winter maintenance equipment and technologies

winter maintenance equipment and technologies
Syntheses of Best Practices
Road Salt Management
Transportation Association of Canada
This is one in a series of Syntheses of Best Practices related to the effective management of road
salt in winter maintenance operations. This Synthesis is provided as advice for preparing Salt Management
Plans. The Synthesis is not intended to be used prescriptively but is to be used in concert with the legislation,
manuals, directives and procedures of relevant jurisdictions and individual organizations. Syntheses of Best
Practices have been produced on:
1. Salt Management Plans
8. Snow Storage and Disposal
2. Training
9. Winter Maintenance Equipment and
3. Road, Bridge and Facility Design
4. Drainage
10. Salt Use on Private Roads, Parking Lots
and Walkways
5. Pavements and Salt Management
11. Successes in Road Salt Management: Case Studies
6. Vegetation Management
For more detailed information, please refer to TAC’s
Salt Management Guide - 2013.
7. Design and Operation of Maintenance Yards
Winter maintenance operating and research personnel
in many parts of the world have identified new methods
and technologies that can improve snowfighting
efficiency and significantly reduce the amount of road
salts used to maintain roads, highways, sidewalks and
parking lots in the winter. Equipment is now available
that incorporates these developments to reduce salt
use, control the impact on the environment, improve
winter travel conditions, safety and mobility, and
reduce overall costs.
equipment and material availability, capability and
limitations in use
snow and ice control strategies and methods
available to them
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pavement and weather conditions that exist, that
are forecasted and that need to be acted upon
Equipment is a significant cost component (along with
labour and materials) in a winter maintenance
program. It is understood that it takes time to adjust
the fleet and to incorporate an acquisition strategy into
When selecting and deploying equipment, proper and
timely information is important to good decisionmaking. In order to properly match equipment and
service delivery in a way that optimizes winter
maintenance performance, winter maintenance
personnel need to understand:
Syntheses of Best Practices
Road Salt Management
an ongoing budget. Further, it is important for an
organization to continuously identify and assess new
and innovative technologies that supports best
practices. Also, there are seasonality and frequency of
use considerations as well as multi-functionality aspects
in evaluating the economics of renewing the fleet.
Management must balance all of the competing
agendas in choosing the preferred equipment
configuration, and a phase-in/out strategy for the fleet,
with an understanding of salt use considerations.
To optimize salt use, it is important to look continually
at new and innovative technologies as they are a
valuable option. Some salt use “optimization factors” to
consider when making equipment choices include:
Winter maintenance equipment is primarily used to
prevent or control accumulations of snow and ice. A
significant amount of the accumulation can be
controlled by mechanical methods such as plowing.
When mechanical methods alone would be
inappropriate or ineffective, deicers must also be used.
For a “saltable” situation, the approach is to place an
amount of material on the pavement to prevent snow
and ice from bonding to the pavement surface, to
control the accumulation of snow and ice and to
achieve bare-and-wet followed by bare-and-dry
pavement within prescribed standards
Improved information and decision making tools
will allow equipment, personnel and salt to be
better used and salt applications better timed.
Efficient mechanical control of snow and ice will
minimize the amount of snow and ice to be
controlled by chemicals.
Proper equipment choices will help operators to
place a predicted amount of salt at the desired
location where it is needed, at the right time.
Chemical applications should occur at a time that
prevents bonding of snow or ice to the surface.
Keeping good records of snow and ice control
actions taken, along with material usage and a
record of changing pavement conditions, will
improve planning and budgeting and limit an
organization’s liability.
The safe and effective use of any equipment
requires operators to be properly trained; this is
particularly important when introducing new
equipment and techniques.
Winter maintenance equipment, once optimized, can
help an organization meet the 4-R’s of Salt
the Right material
the Right amount
the Right place, and
the Right time.
Information & Decision-making Tools
To make the best use of available equipment and
personnel and meet the 4 R’s of Salt Management,
experienced decision-makers in winter maintenance
operations need information to support their judgment.
In addition to the 4-R’s, a final key to effective salt
management is:
The critical information required can be divided into
three categories:
Keep it on the pavement to work
Each organization will need to assess the winter
materials available, to determine appropriate
application rates for a given situation and determine
the best time for application in order to achieve the
established level of service.
weather and pavement forecast information
(what will happen), for predicting upcoming
storms and potential icing events
current information (what is happening), providing
surface temperatures and conditions, and
Following a principle of determining what is “right” for
a given organization, considering the 4-R’s will help any
winter maintenance operation optimize the use of salt.
Public safety will be maintained while controlling the
impact of salt on the environment.
status information (what did happen), recording
what was done and the Level of Service achieved.
A number of tools are available to help provide the
required information. Typical examples follow.
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Syntheses of Best Practices
Road Salt Management
Sensor-based RWIS has been in use since the mid 1970s
by road and airport authorities around the world. The
Canadian network of RWIS stations has grown
significantly in the past decade. Beyond giving road
information and trends, RWIS sites and networks
provide information required to develop specific
forecasts as well as some service documentation.
RWIS supports winter operations in the following ways:
An understanding of pavement temperature
forecasts and trends can improve the accuracy of
Sensors embedded flush in the pavement, as well
as sub-surface, generate data that can be sent
back to central locations allowing trends and
forecasts to be developed.
Pavement sensors can monitor pavement
temperature, wet/dry status, freeze point of the
solution on the pavement, presence of chemical
and concentration (for some chemicals), as well as
subsurface temperature.
Tower-based sensors can also provide real-time
information of typical atmospheric conditions such
as precipitation, relative humidity, dew point, air
temperature, and wind speed and direction.
Weather forecasting services can use road-based
information to provide “road weather” forecasts
to help the snowfighters make better decisions
regarding snow and ice control.
Salt use optimization is achieved by more accurate
deployment of equipment and application of
Other types of sensors, cameras and systems can
be added to RWIS to further support snowfighters
(e.g. automated liquid deicer application system –
Fixed Automated Spray Technology (FAST),
cameras, remove pavement and friction sensors,
Both hand-held and truck-mounted versions are
available; with the mounted versions measuring
ambient air temperature as well. There are also
units that include a humidity sensor thus allowing
the dewpoint temperature and relative humidity
to be measured.
Truck-mounted versions allow continuous
monitoring of the road surface while the vehicle is
moving along the road.
The data can be recorded and transmitted as part
of the data stream of a GPS/AVL system (see
Operational Support Equipment later in this
Stationary pole mounted remote surface
temperature sensors are also available. These can
provide the surface temperature, air
temperature, dew point temperature and relative
humidity at the specific location. Because they are
mounted at the edge of pavement, they avoid the
disruption associated with installation of inpavement sensors.
Like all equipment, IRTs need to be checked and
calibrated to confirm their accuracy and to be
confident in the reading.
Not all of the IRTs on the market can be recalibrated. A simple way to check the accuracy of
an IRT is to create a water/ice mixture and
measure the temperature of the surface of the
mixture with the IRT. If the IRT is accurate it
should record 0o C. The difference between the
reading and 0o C will provide the accuracy. It is not
unusual for a hand held IRT to have a 1-2 degree
Moisture, snow and ice degrade surface friction
producing slippery conditions. Road salts and,
sometimes, abrasives like sand, are applied to improve
traction, increasing the coefficient of friction. Decisions
about material application can be improved by having
better information about the current friction level of
the surface:
Decisions about material application are improved by
knowing the current road surface temperature and the
temperature trend. There are portable or stationary
infrared thermometers on the market that can be used
to determine the current surface temperatures.
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The presence of precipitation or applied winter
materials such as anti-icing liquids, sand and salt
can provide inconsistent friction across the
pavement surface.
Syntheses of Best Practices
Road Salt Management
Road authorities around the world are working
with suppliers to develop reliable and accurate
equipment to measure the available traction on
Friction sensors have been used extensively on
airport runways, but their high cost is currently
restricting widespread use on roads. Alternative
designs promise lower cost.
In some cases friction sensors are mounted on the
spreader vehicles and used in conjunction with onboard mounted pavement temperature
measurement equipment to automatically control
the application rate of snow and ice control
Using Mechanical Means to
Control Snow and Ice
Mechanical removal of ice and snow is usually
preferable and this can be facilitated by preventively
treating paved areas with road salts. Such pre- or earlystorm applications will often minimize the overall
amount of road salts required to achieve the desired
surface friction level. Reacting to a snow and ice event
and applying road salts after a bond has formed
requires significantly more salt to be used.
Some organizations choose to leave a small amount of
snow on the pavement before salt is applied in order to
keep the salt from bouncing or being blown off the
surface by traffic or wind.
Alternatively, the device could be mounted on a
“smart patrol truck” with other winter
maintenance tools.
There are also stationary sensors available that
are pole mounted. These use infra-red beams to
determine the pavement condition (e.g. dry,
moist, wet, icy, snowy/frosty or slushy). They can
also measure friction.
Technically, the equipment can be accurate and
dependable, and has the potential to eliminate
the unnecessary use of salt where adequate
traction exists.
Accumulated snow and ice or slush can be controlled
mechanically by removing it with plows mounted on
trucks, motor graders or loaders. Snow blowers and
power brooms are also used in some areas. Repeated
plowing operations in areas with limited snow storage
will require the stockpiled snow to be removed for
disposal. The following discussion provides a general
overview of snow removal equipment and some
advantages and disadvantages of their use.
A wide range of plowing options are available including
the type of vehicle used to carry the plow, the type of
plow and mouldboard and even the type of cutting
edge or blade.
After a storm event has passed and the pavement has
become bare and dry, there often is a residue of
chemical remaining on the surface. This fine layer of
chemical will be activated with the next precipitation
event. This residual will also help to prevent the
formation of frost and can melt a small amount of
snow. As well the concentration of salt contained in
slush is the determinant of the freeze point
temperature of the slush. It is helpful for decisionmakers to know the residual salt concentration on the
pavement. An RWIS pavement sensor will provide this
information. Portable salinity sensors are also available,
although their cost and the fact that one needs to
stand on the pavement to take the measurement,
make widespread use impractical. Another tool being
tested is a “chemical presence” sensor that can
measure the chloride concentration of pavement spray
in a vehicle’s wheel well.
The vehicle type and size must be selected properly to
be able to operate in the required area, carry and
operate the mounted equipment and provide a safe
and comfortable environment for the operator.
Vehicles may also be multi-purpose, and be used for
other duties during non-storm event times and during
the off-season, summer months.
Considerations for typical units in use include the
Trucks come in various capacities and dimensions,
and are commonly referred to as single axle,
tandem axle or tri-axle units.
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Smaller, more maneuverable vehicles may be
more suited to urban operations, parking lots and
sidewalks, whereas larger, more powerful trucks
may be preferred on roads and large parking lots.
Underbody plows can also be mounted on trucks
and be used with down pressure.
Trucks with front mounted plows and wings often
provide the best solution on roads as they can
operate at higher speeds. This allows roads to be
cleared sooner and allows the truck to operate at
safer speeds. Trucks operating closer to the speed
of other traffic present less of a safety hazard.
Higher operating speeds may be inappropriate in
urban areas and in proximity to environmentally
sensitive areas where snow thrown beyond the
edge of pavement could damage roadside
features and the environment.
Trucks can be configured with a hopper or tank to
serve the dual-duty role of spreading materials as
well as plowing.
Careful attention must be paid to the truck
specification to configure it as a frame-stiffened
winter truck of suitable horsepower and
hydraulics, rather than simply a generic cab-andchassis off the production line.
municipalities and contractors during the summer
for road construction and maintenance, and are
little used otherwise during the winter.
Trucks operating at higher speeds can effectively
“throw” snow a sufficient distance back from the
edge of the shoulder to minimize snow bank build
Syntheses of Best Practices
Road Salt Management
Graders are useful when working in tight quarters
on urban streets with cul-de-sacs, elbows, bus
bays, and varying road widths.
They work at lower speeds and promote a safer
operation when working in the presence of
pedestrians and heavy traffic because of enhanced
operator visibility.
They can be fitted with front plows, including one
way and reversible plows, “V” plows, and side
wings, with or without driveway gates.
Graders can also be mounted with a tooth or
stacked-disc ice blade to scarify hard ice-pack and
provide improved, temporary friction.
Modern graders can operate at much higher
speeds than older models but are limited to thirty
to thirty-five kilometres per hour and thus are
slower than truck mounted plows.
Graders are effective during fall freeze-up and
spring thaw when roads are soft and susceptible to
digging-in by truck-mounted plows.
Loaders are occasionally fitted with plows, wings
and snow blowers for snow removal.
Modern loaders with large glass areas on the sides
and front, and a high mounted operator position,
provide the operator with excellent vision of the
area around the loader.
Front axle capacity is a consideration, and the
vehicle should meet legal weight requirements as
Loaders (particularly articulated loaders) are
useful when working in tight quarters on parking
lots and urban streets with cul-de-sacs, elbows,
bus bays and varying road widths.
Trucks require locking differentials or electronic
traction control to prevent traction loss due to a
spinning wheel.
They can also be used to pick up and remove snow
on parking lots, cul-de-sacs, bridges and other
tight areas with limited snow storage.
Loaders are readily available for winter road
maintenance as they are widely used by
municipalities and contractors during the summer
for road construction and maintenance and are
used extensively to load sand and salt onto
spreader trucks at the maintenance yards.
Loaders are also an important tool for loading
materials into spreaders. The buckets must be
To ensure adequate traction and load baring
capacity, both front and rear tires must be
selected carefully to ensure suitable tread
pattern, material and sufficient load rating to
handle both the material load and plows.
Motor Graders
Graders are often fitted with plows and wings to
remove snow.
Graders are often readily available for winter road
maintenance as they are widely used by
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Syntheses of Best Practices
Road Salt Management
sized for the spreaders being loaded so that
spillage of materials is limited.
Front Mounted One-Way Plows
That Move the Snow to the Right
Front mounted one-way plows are designed to move
snow to the right side for plowing roadways. The
following are their characteristics.
The type of plow and cutting edge must be
selected properly to be able to be mounted
properly on the vehicle, to operate in the required
area and achieve the desired performance in snow
The selection of the appropriate type of plow and
proper adjustment of the plow will reduce costs
and lessen the amount of salt needed to clear the
Plows should be operated with sufficient weight on
the blade to effectively cut through packed snow
and ice, resulting in a near-bare surface, in order
to minimize the amount of salt required to fullybare the pavement.
Plows for high speed operations should be fitted
with shoes to prevent the plow from dropping into
holes or catching on obstructions. In low speed
operations (e.g. parking lots) the shoes are usually
removed to maximize snow removal.
Plows should be adjusted to minimize the amount
of weight carried on the shoes, but the shoes
should be close enough to the pavement to absorb
the weight of the plow if the plow strikes an
obstruction. Castors are sometimes substituted for
shoes to minimize wear.
Plows should be fitted with a tripping mechanism
that will reduce damage to the plow if it impacts
catch basin or manhole covers, curbing or other
obstructions. The trip mechanism will also prevent
the truck from being violently deflected from its
traffic lane.
Various plows angles are used depending on the
goal. An angle of about 75° between the blade
and the pavement provides the most effective
cutting of heavily packed snow and ice. An angle of
55° between the blade and the pavement is the
most efficient at moving large quantities of snow
and causes the least amount of snow to be blown
up at the front of the vehicle. One jurisdiction has
used a 40° angle to improve snow pickup.
This plow provides the most efficient blade
available for plowing snow.
The snow is not thrown as far at the outlet end of
the plow so more snow remains on the shoulder.
The standard shape allows more snow to escape
from the mouldboard and contributes to a cloud of
snow surrounding the truck. Newer designs
improve driving safety by minimizing the amount
of snow that escapes into the snow cloud at the
point of impact.
These plows commonly are used for high-speed
removal of snow, slush and packed snow.
They can be used to clear from minor amounts up
to approximately 50 cm depths of snow at
highway speeds;
Steel one-way plows can be large and heavy;
therefore the truck must be fitted with a high
capacity front axle, and heavy duty wheels and
The size of the vehicle may be a disadvantage
when clearing snow in congested urban areas and
subdivisions with cul-de-sacs, etc.
Piston-like cushions are available to reduce the
pounding/bouncing of the blade on the road
surface, which reduces the impact on both the
truck and operator.
These plows should be fitted with nose points to
prevent the plow from catching on bridge
expansion joints and cross cracks.
A thorough training program is required to ensure
that the operators are familiar with the
adjustments to maximize snow removal and
maintain all safety features in a fully functional
Either right and/or left side plow wings are usually
fitted to extend the plowing width (see Wings or
Various designs and improvements to
aerodynamics have been made to improve the
operators’ visibility by trapping some of the snow
cloud kicked up by the cutting edge.
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Road Salt Management
Front Mounted Reversible Plows
Wings improve efficiency and allow for increased
snow removal, being especially useful in multi-lane
clearing and when operating in an echelon
formation since they help prevent leaving a
windrow of snow on the traveled surface.
Wings may be inappropriate in some urban
settings where they can throw snow beyond the
edge of pavement and damage roadside features.
Usually the vertical angle of the plow can be
adjusted by a cable/chain or hydraulically, allowing
the wing to be used for clearing shoulders or for
cutting side banks of snow.
Front mounted reversible plows are used to move snow
to the left or right side of the truck. The following are
some of their characteristics.
These plows are useful for clearing left hand lanes
(especially adjacent to a median) and ramps.
They are widely used in urban areas because of
their versatility.
Some manufacturers offer reversible plows with
mouldboards that can be reshaped to match the
shape of one-way plows when the mouldboard is
angled in either direction. These plows have been
strongly endorsed by the plow operators, but are
significantly more expensive.
Underbody Plows
The underbody plow is suited to applications on
crowded urban streets, urban laneways and back
alleys, as well as in some rural settings.
They effectively serve as a two-way reversible
plow and are normally stable.
Front mounted “V” plows effectively handle
deeper accumulations of snow.
They are effective in clearing highly compacted
snow and ice by way of variable downward
pressure, using the truck’s compressed air system
or hydraulic pressure and springs, to maximize
These plows have been designed to lift snow over
adjacent windrows and to balance side loading by
pushing snow to both sides.
These plows are limited to clearing snow
accumulations up to 30 cm.
Their use is now restricted mainly to areas with
high snowfall rates and as back-up units to open
roads closed during severe storms.
Underbody plows are not normally used with side
wings so the plowed path is limited and a lane-side
windrow of snow is created.
A rear mounted snow wing can be added to trucks
with underbody plows but the plowing width is less
than that of a front mounted wing. With this
configuration the vehicle might be expected to be
less stable than front mounted wings as the side
thrust from the wing is located further from the
centre of gravity of the truck.
In some cases the vehicle might be less stable due
to excessive down pressure.
§ A unique variation of the reversible plow is a
centre-hinged-reversible plow that can push left or
right or effectively become a V-plow.
The plows may be fitted with nose points to
protect against catching on minor roadway
obstructions, bridge expansion joints, etc.
Front Mounted “V” Plows
A smaller version of the v-plow is often used to
clear sidewalks.
Wings or Wing-plows
Wings are smaller side-mounted plows that can be
mounted on a tower or mast near the front of the
plow truck, or further to the rear at the back of
the cab.
Wings can also be mounted on graders.
They can be mounted on either or both sides of
the plow vehicle, and effectively increase the
width of the plowed path.
One disadvantage of wings is that operator
visibility can be impaired.
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Vertical Plows
A recent development in plows is the vertical
blade which is flat but hinged in two locations (at
third points) so as to push straight, right or left, or
to effectively scoop snow by catching it and
pushing it forward.
Syntheses of Best Practices
Road Salt Management
This plow is usually loader or tractor mounted, and
can accommodate a snow load traveling at slower
speeds either forward or in reverse.
Ice blades are used to cut into hard packed snow
and ice that cannot be removed with conventional
A vertical plow is preferred in areas of unique
geometry, or where access is tight.
Special plow blades with sliding segments that
move up and down vertically facilitate the
thorough clearing of rough or distorted pavement,
reducing the amount of salt required to bare off
the pavement. The manufacturers also claim that
these blades minimize damage to the plow and
truck from hitting obstructions, such as catch basin
covers, as less force is required to retract one
segment clear of the obstruction. These blades are
well suited for high speed and rural plowing.
Tow Plows
Tow plows consist of a secondary plow towed on a
trailer behind a plow truck.
They are used to plow multiple lanes with one
truck on urban multi-lane roadways, rural high
speed highways, climbing and passing lanes and
rural shoulders.
The operator can raise and lower the tow plow
blade and swing the plow out into the adjacent
lane allowing a single truck to clear a width of
more than 7.3 meters (24 feet) – the equivalent to
2.5 conventional trucks. This generates over 30%
savings on equipment, fuel and manpower costs.
When not needed, the operator can raise the
blade on the tow plow and redirect the unit back
behind the truck.
Tow plow trailers can also be outfitted to spread
conventional materials or with liquid tanks for
applying straight liquids at the same time the road
is plowed. .
Over the course of a winter and multiple plowing
operations snow will build up along roadways or in
parking lots. Areas with limited space for plowed-snow
storage may develop visual obstructions for drivers, act
as a snow fence causing drifts to form a cross roads,
restrict use of the facility and prevent future plowing
operations from being productive once the snow
capacity of the area is exceeded. In addition,
accumulations next to guide rail, barrier walls and
bridge approaches can freeze solid and create an
unsafe ramping condition.
The piled snow, containing salt and other road
contaminants, may need to be removed and disposed
of or stored in an appropriate manner. Refer to the
Snow Storage and Disposal Synthesis of Best Practices
for more information.
Cutting Edge or Blade
Snowplow cutting edges and blades are available
in various designs and configurations for various
Regular blades are made of heat-treated steel or
fitted with tungsten carbide inserts to improve
durability (by a factor of up to eighty times in high
speed operations).
Rubber and polymer/plastic blades have been
tried to minimize damage to catch basins, bridge
expansion joints, centerline pavement markings
and raised reflective markers, etc. These blades
can be used to effectively “squeegee” the surface
to remove slush in areas where the ambient
temperatures usually rise above the freezing point
during daylight hours after a storm. In areas with
colder temperatures the use of theses blades has
not been as successful.
Snow removal is usually considered a fair-weather or
clean-up operation, and may entail traffic control
considerations. Also, most removal operations often
leave some snow on the road that must then be
treated with abrasives or snow and ice control
chemicals to maintain safe driving conditions.
Various removal methods and equipment are available
and should be selected based on local needs. The
following discussion provides a general overview of
methods and equipment used to remove and dispose of
accumulated plowed snow, and some advantages and
disadvantages of their use.
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Road Salt Management
Snow bank accumulations may simply be handled
by a conventional plow truck and physically
relocated further back beyond the roadway and
Snow melters melt snow that is picked up and
place into a heated box. The resulting melt water
is usually drained directly to the storm sewer
High-winging or stepped-winging commonly is
used to cut the bank height.
In a rural and/or urban environment, a grader
with or without a wing can be used to move the
snow further back to create space for subsequent
plowable storm events or to act as a barrier (snow
ridge) instead of using a snow fence.
Melters provide a solution for unique problem
areas, particularly tight urban areas with limited
snow storage available adjacent to the road on
the right-of-way. They are also used to melt snow
in parking lots where snow volumes are restricting
usable parking spaces or meltwater is causing icing
Alternatively, the bank may be cut forward,
toward the roadway, immediately followed by a
full speed one-way plow run that effectively
throws the loosened snow to the fence line.
Melters may be an economical solution where the
hauling costs are high (i.e. where snow disposal
facilities are far from snow removal locations.
Melters can be mobile or stationary.
Mobile melters move under their own power and
picks up the snow by a conveyor and delivers it to
an onboard melting tank and the melt water is
released to the drainage system. The production
of mobile melters can be quite slow.
Stationary melters are melting tanks that are
moved and set up at where the demand for
melting exists. Snow is trucked to the melter. In
some cases these are a temporary set up where
once the melting operation is completed, the tank
is moved to its home base. In other cases they are
permanent set ups.
Where sanding is a major activity in a winter
operation, there can be a problem with plugging
when melting sand-laden snow.
Snow melters may have water/waste treatment,
noise and air emission issues (see Snow Storage &
Disposal Synthesis of Best Practices).
Loading, Hauling and Dumping
The most cost effective and easily mobilized
removal operation for isolated locations is by
means of a loader that fills conventional
contractor dump truck(s), which then haul the
snow to an appropriate site.
The capacity of the loader and the truck body will
determine the production rate and effective cost.
Auxiliary equipment may be required to increase
the efficiency of the operation. For instance, a
grader may “peel” a snow bank into a suitable
windrow in order to accommodate the loader and
truck position.
Since a loading operation necessarily impacts the
flow of traffic in the area, traffic control or
protection is often required, and consideration
should be given to doing this work at night.
Mobile Conveyors
Mobile conveyors are used to load snow from the
shoulders or a windrow directly into trucks for
They can operate entirely on the shoulder with
both the unit and the truck being loaded lined up
on the shoulder with minimal traffic disruption.
While blowers can be used during storm
conditions, they are a slower production unit than
a plow and are normally used for post-storm snow
They are useful in areas with high traffic volumes
or limited access
Blowers are also used to load trucks for snow
removal in urban areas, along roads and in parking
lots with limited snow storage space.
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Syntheses of Best Practices
Road Salt Management
They are often owned by contractors or are a part
of an equipment fleet that services a network of
open roads in an area with very high snowfall
All blower operators must be aware of wind
direction and the visibility concern that traffic
could encounter.
Blowers are typically mounted on dedicated
trucks, tractors or are attached to large front-end
They are available with hydraulic powered vanes
to control the direction of the blower in snow
Preventing a snow and ice bond to the pavement
surface should be the top priority. If prevention efforts
from early-storm treatments fail and a bond forms,
then destroying this bond must be done as quickly as
possible. There are many chemicals including road salts
that prevent and/or destroy that bond, making
mechanical removal easier, and melt that portion of
the frozen precipitation that cannot be removed
mechanically. The key is to apply the right amount of
the right material, in the right place and at the right
time. Various chemical control strategies are available.
There are a number of liquid deicers available. Most of
these liquids are chloride based and are manufactured.
Sodium chloride brine is commonly used because it can
be made from rock salt by the user inexpensively and its
performance is well understood. There are also natural
brines available that contain a mixture of chlorides.
Newer liquid products include organic byproducts such
as beet juice and carbohydrates (condensed distiller
soluble) that claim to reduce the amount of salt
needed, reduce the working temperature of the
mixture, reduce vehicle corrosion, increase residual and
inhibit the refreeze process.
The following discussion provides a general overview of
methods and equipment used to apply salt and sand,
and some advantages and disadvantages of their use.
Some liquid road salts such as calcium chloride and
magnesium chloride are exothermic (give off heat) and
therefore can act synergistically with sodium chloride
which is endothermic and requires heat to create brine.
Anti-icing can involve application to the pavement
of liquids, pre-wetted or pre-treated solid granular
materials or dry granular material. Thus, anti-icing
is not confined to using liquids.
Anti-icing creates a safer condition, quicker and
with less chemical than does deicing.
Liquid deicers are popular because they are already in
the state necessary to melt snow and ice. As such they
enhance the melting performance of deicing chemicals.
They also help to keep solid materials on the surface
longer. For these reasons and others, liquid deicers are
being applied through direct liquid application (DLA) or
to sand and solid salt - either through pre-treatment of
stockpiles or through on-board pre-wetting. These
techniques are discussed later.
Using Road Salts to Control Snow and Ice
A solid chemical must first dissolve in water, creating
brine, before it can melt snow or ice. The lag time while
solids dissolve delays the effect of the chemical
Blowers can be used simply to widen the snow bank
area and relocate the snow by blowing it beyond the
bank toward the ditchline (where storage capacity is
Anti-icing is the proactive use of any melting agent
to assist melting and resist the formation of a bond
between snow and ice and the pavement surface.
Deicing is a reactive strategy of destroying an
existing bond between snow/ice and the
pavement where a chemical is applied after the
bond has formed between the snow and the
pavement. In these cases the chemical must work
its way through the snowpack to the pavement
surface where it can break the bond and allow the
snow to be removed mechanically.
Liquid Deicers
They may also have hydraulic controls on the
chutes to accurately direct the snow into the
trucks used for haulage.
Direct Liquid Application (DLA)
Direct liquid application (DLA) is the placement of
a liquid deicer directly onto the pavement surface.
April 2013
DLA is efficient since it provides immediate melt
action and does not take the time to dissolve and
form brine that a solid chemical does. As well,
liquids do not depend on the presence of heat
from the ground, sunlight or traffic to dissolve
(endothermic reaction).
Generally, an equivalent weight of salt applied as a
liquid (e.g. dissolved in water) performs better
than the same weight of dry granular salt because
the liquid is fully retained on the pavement
The cost on a dollar-per-gram basis may be
greater for liquid only applications (depending on
the liquid used); however the merits of DLA should
be assessed on a full cost basis including the
offsetting safety benefits.
The timing of the application of DLA is not as
critical as with granular materials. One significant
advantage of using a liquid is that it can be applied
to dry pavement in advance of the start of a storm
provided conditions suit the use of DLA. The
resultant residual chemical will be present when
the event (frost or snow) occurs. This means that
roads, parking lots and sidewalks can be treated
during times when traffic is low or parking lots are
Syntheses of Best Practices
Road Salt Management
Where the application is earlier than the onset of
a storm, the water in NaCl brine will evaporate
leaving a salt crystal residue in the surface pores/
texture of the pavement. This residual will later
dissolve and form brine when moisture becomes
present (either from precipitation or dew).
Liquids can also “scrub” the oils from the pores of
pavement, especially with an application after a
prolonged dry period. The resultant slurry can be
slippery. It does not take a lot of liquid to achieve
the desired anti-icing effect. Over applying a liquid
can cause some of these slipperiness conditions.
The impact of this temporary effect can be
minimized by using pencil nozzles that leave
alternating dry and wetted strips on the
The approach to resisting the bond is not to wet
the pavement, but simply to provide enough
chemical to enhance early-storm safety with an
application of chemical that stays on the
pavement surface. In most cases, the intention is
not to “wash” or even fully wet the pavement with
an equivalent chemical loading as that of a
granular application.
It is acknowledged that a direct liquid application
has much less “staying power” than granular salt;
however the use of this procedure lessens overall
chloride loadings per storm and allows for bare
pavement to be achieved sooner.
The application of liquids can be triggered by
sensors and sprayed on a surface such as a bridge
deck using Fixed Automated Spray Technology
DLA can be applied over multiple lanes by trucks
traveling at higher speeds (than conventional salt
spreading) with due regard for traffic.
Trucks used for DLA can range in size, to
accommodate frame-mounted or slide-in tanks.
Truck configurations may include:
Conversely, hygroscopic brines (such as CaCl2 and
MgCl2) will attract moisture and continually wet
the road until they are dissipated.
There is evidence that as chemicals move from a
liquid state to a solid or from a solid to a liquid,
there is a short period where a “slurry” state can
occur. With some chemicals this “slurry” state can
reduce friction on the pavement creating a shortterm slippery condition. Humidity is the most
important factor in creating this slippery
condition. Temperature also seems important.
Higher temperatures and lower humidity can dry
out a solution creating the liquid-to-solid
transition. On the other hand with high humidity, a
dry chemical residual can re-hydrate causing a
solid-to-liquid transition. This is more of an issue
with hygroscopic chemicals.
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small trucks ranging from pickups and two-tons
with tanks or collapsible bladders, to vehicles
used for vegetation spraying or bridge washing
in the off-season
- larger trucks used for water applications or
calcium dust suppression applications in the off
season, and
- full-size, larger capacity tractor trailer tanker
units used for long distance hauling in the off
Trailer-mounted tanks are also used.
Custom built units may be required for specialized
high-speed, multi-lane, long-range applications, or
small scale operations such as sidewalks and
transit platforms.
Syntheses of Best Practices
Road Salt Management
Mid-sized trucks used for DLA can also be outfitted
with a plow and wing harness for subsequent use
later in the storm.
Tank, pump and nozzle configurations, as well as
the controller, will determine the preferred
application practice and route range.
The liquid is delivered to the pavement by means
of pumps or gravity-fed nozzles. The preferred
applications makes use of “pencil-sized” streams
at 200 mm to 300 mm spacing; this prevents
misting or atomizing the liquid that then blows
away and doesn’t make it to the road surface.
An alternative to pencil-nozzles is the use of tubetrailers that run from each nozzle to the road
surface and directly target the liquid without the
stream passing through the air; though the tube
has to be adequately clamped and will wear from
the pavement surface, it better targets the liquid
onto the pavement.
Pre-wetting provides significant potential for
reductions in salt use but can increase the
complexity of the required equipment and
Pre-wetting requires additional equipment.
Storage tanks for the liquid(s), or brine making
equipment are required, along with pumps to load
the spreaders.
The on-board liquid capacity and loading time are
factors to consider.
The application pumps on the spreaders should be
regulated by ground speed controllers to ensure
the correct liquid application rate is maintained
under all conditions.
Additional maintenance is required such as
ensuring that the liquid filters, lines and nozzles
are purged and the equipment cleaned at the end
of the storm to prevent clogged lines and seized
Pre-wetting is a commonly used practice to
improve performance and keep material on the
pavement by reducing the effects of bouncing,
blowing and sliding of the salt or sand particles.
This technique uses a liquid chemical to wet the
sand or salt as it is spread on the pavement.
Pre-wetting enhances the melt action of the
chemical present by speeding the dissolving of salt
and the formation of brine.
Pretreatment is the addition of a liquid to solid salt
at the time it is stockpiled.
Pretreated salt can have the same benefits as prewetted salt without having to invest in new
equipment thus providing an easy entry into the
use of liquid technology.
Practical considerations relate to the gradation of
the salt being wetted, the maximum liquid to solid
ratio that can be mixed, the amount of mixing
action, caking/clumping concerns, etc.
Adjustment of the spray nozzles is critical. Tests by
one US state department of transportation
showed that they never achieved more than 60%
coverage of the salt. The remaining 40% of the
pre-wetting liquid was effectively being applied
directly onto the pavement.
As the wetting agents are corrosive, it is
important that corrosion resistant nozzles and
non-contact pumps are used to ensure dependable
The total amount of salt used for winter
maintenance is significantly influenced by the
characteristics of the spreader equipment.
Spreader controls must be capable of delivering
several precise application rates.
The application rate should be consistent whether
the spreader is full or nearly empty, regardless of
material variations, or temperature changes.
When purchasing new equipment, organizations
should require test results from suppliers to
confirm that the equipment will achieve precise
application rates under all conditions.
Spreaders must operate in a severe environment
of low temperatures, high moisture, poor visibility
and corrosion.
Spreaders must be easy to load, and simple to
April 2013
Ideally, a spreader should be adaptable for other
tasks, or the hopper should be easily removed so
the trucks can be used for other operations during
the summer.
Hoppers must be constructed so that all sand and
salt can be easily removed from the body.
Spreaders should be fitted with screens to ensure
that frozen clumps of material or other
contaminating material that would jam the chain/
conveyor mechanism are not loaded into the
Cab shields should be fitted to assist in loading the
spreaders to ensure that all loaded salt enters the
box, and material is not spilled over the truck or on
the ground.
Spreaders should be manufactured from a
material that will resist corrosion. Special
chlorinated rubber primers and epoxy-based
primers will increase coating life. Stainless and
galvanized steel and fiberglass bodies are available
but can be relatively expensive. High strength, low
alloy self-coating steel, used with good surface
preparation and special primers has been proven
to provide a cost effective body life of up to fifteen
years. Manufacturers also supply spreader bodies
constructed of fiberglass. These bodies are lighter
and thus provide increased payload possibilities,
but are also more expensive than steel.
Electrical wiring for controls and lighting, and
hydraulic components must be enclosed in vapour
proof, or sealed systems.
Neoprene spinners are frequently used to improve
durability and spreading efficiency.
Syntheses of Best Practices
Road Salt Management
solution drains down the crossfall of the road, and
can migrate under packed ice and snow; a uniform
section of road is then bared off initially along the
centre of the road to provide two-wheel stability
for traffic. This reduces the unnecessary loss of salt
that can come from broadcast operations.
Application in a windrow is achieved without using
the spinner, by dropping the material from a
chute. In some cases the salt is dropped onto a
slowly rotating spinner centered over the crown.
Windrowing on the centre line will not work if the
crown of the road is not consistently on the
centerline, or the road surface is badly
deteriorated which could cause the salt brine to
pond in some areas.
Centre line application is not appropriate if the
entire road surface is slippery and immediate deicing is required. In these situations, higher salt
application rates may need to be spread across all
traffic lanes using a spinner.
Some rear-discharge spreaders have the ability to
vary the spread pattern (widths and symmetry)
allowing the operator to adjust the spread pattern
to unique road network conditions. For example to
pick up an acceleration/deceleration lane or bus
stop or to address a super-elevation.
Application ahead of the drive wheels can provide
improved traction under the drive wheels of the
spreader vehicle. Application close to the driver’s
cab also enables the driver to monitor the
application to ensure that material flow has not
been impeded.
One argument in support of rear-discharge
spreaders is that the drive wheels should not have
enhanced friction if the steering wheels do not
also have the benefit of improved friction.
Otherwise, the driver may not be able to control
the steering as the front wheels slide while the
drive wheels continue to push forward. This is not
normally an issue on bare-pavement policy roads
unless there are significant grades in the area.
Spreaders designed with discharge at the rear can
allow for a slide-in capability that can be mounted
and dismounted quickly.
Discharge at the center-rear of the vehicle is
simple but may restrict the vehicle to treating the
lane in which the vehicle operates; some designs
Spread Patterns
Salt and sand application methods can be modified
to meet differing requirements.
Typically one of two spread patterns is used: i)
Placing a windrow on the crown or high side of the
pavement; and ii) Broadcasting material uniformly
over the pavement.
In most cases on roads, solid or pre-wetted salt
should be applied in a continuous narrow windrow
along the centerline of the road. The
concentrated mass of material minimizes the
tendency of the material to bounce or be blown
off the road by passing traffic. Salt going into
April 2013
Syntheses of Best Practices
Road Salt Management
allow for the spinner “throw” to place the
material at an offset from the vehicle.
Broadcast spread patterns are suited to situations
where broad coverage is needed immediately. This
is typical on parking lots and sidewalks.
Broadcast spreading is also appropriate on roads
where immediate traction and melting over the
entire surface is required. This would be in the
case of freezing rain or black ice or when placing
gasoline or diesel engine. Though a few are still in
use, these engines are problematic and a constant
source of downtime and maintenance. Reliable
hydraulic pumps, driven from the truck engine, are
now common.
Conventional hopper spreaders provide good
control of material application and dependable
service. However, they are the least versatile for
other operations during the off-season.
New hopper designs, including rear-discharge,
slide-in units with a longitudinal agitator bar and
belt conveyor is gaining popularity, particularly for
pre-wetted applications.
Drop spreaders are best for sidewalks because the
material can be confined to the sidewalk and not
lost to the vegetated areas.
Tailgate Spreaders
Manufacturers provide different spreader types to
meet various requirements. The various designs have
different characteristics that must be considered when
a spreader is selected for a particular application.
These include hopper spreaders, tailgate spreaders,
reverse dumping spreaders, and some new variations of
these types.
Tailgate spreader units mount on the rear of the
truck dump box and are filled by raising the body
and dumping salt into the integral hopper. The salt
is then conveyed to the spinner by a chain or auger
and applied in a windrow or broadcast over the
surface using a spinner.
These spreaders are considered a simple and
dependable unit. They are used extensively in
areas where storms are less frequent and the
trucks can be used for other purposes, or as
backup units for hopper spreaders.
Their primary limitation is the inconvenience of
raising the dump box and the possibility that the
box will not be raised high enough to ensure that
sufficient material is dumped in the hopper to
provide consistent delivery.
The rear discharge restricts the operator view of
the operation and ability to ensure that the
material is being discharged at the right location.
The vertical clearance and the upward and
rearward shift of the centre of gravity when the
box is raised can cause instability and can be a
safety concern.
Hopper Spreaders
Hopper spreaders have provided optimum
performance and durability in the past.
These spreaders are usually installed on trucks
during the winter and removed and replaced by
standard dump bodies or other equipment for the
summer (e.g. water tanks, concrete mixers, etc.).
The design incorporates steeply sloping sides to
eliminate material hanging up.
A conveyor chain, belt or auger is used to move
the material to the discharge location. Conveyor
chains have proven over the years to be more
trouble free than belts, and both can be more
accurately calibrated than augers.
Augers have shown very high wear and poor
accuracy in material control.
The application rate of the material being spread
is controlled by adjusting both the speed of the
chain used to convey the material to the chute or
spinner and the gate opening on the body.
These spreaders were developed to overcome
problems identified for tailgate spreaders while
still providing a multi-purpose spreader that could
be used year round.
A constant source of power to drive the hydraulic
pump was once provided by an integral small
They function as regular rear dumping bodies
when not being used to apply winter maintenance
Reverse Dumping or Dual Dump Spreaders
April 2013
Syntheses of Best Practices
Road Salt Management
The pivot pins can be repositioned so the standard
hoist can be used to raise the rear of the body. This
moves the salt or sand to the chain conveyor at
the front of the body that moves the material to
the distribution point ahead of the rear wheels.
These spreaders have the advantage of providing
year round service and can be switched from
hauling construction materials to winter
maintenance use with no adjustments required.
Disadvantages of this spreader are the high
weight compared to a regular dump truck, and
the need to raise the body while driving to move
the material to the front of the truck. This reduces
the truck’s stability and care is required by the
operator to ensure that sufficient material covers
the cross conveyor at the front to maintain a
precise application rate. The pivots have been a
source of failure and replacement is expensive.
A variation of the reversing dump body is the sidetipping floor. The floor and passenger side of the
box are raised to move sand or salt to the driver’s
side of the truck where a longitudinal conveyor
moves the material to the front of the box for
distribution ahead of the rear wheels. This
arrangement eliminates the strong weight shift to
the front of the vehicle and the material is
distributed ahead of the rear wheels where the
operator can easily monitor the application. The
complexity involved in ensuring that the box is
tipped far enough to cover the conveyor is a
disadvantage. Some problems have been
encountered with body integrity, as the full
support of the contractors dump box is not
available. The vehicle is also more heavily loaded
on the driver’s side and braking on slippery roads
could be affected.
A lateral conveyor at the front transports the
material to the left or right side of the body for
distribution ahead of the rear wheels.
The material is either discharged in a windrow
using a chute for concentrated action, or spun
across the lane using spinners.
The spreader provides precise application rates
and all the advantages of distribution in front of
the rear wheels.
The cross conveyors are easily removable during
the summer so that there is no tare weight
The units are lightweight and provide year round
The body can be easily switched to carrying
construction materials (simply by installing a pan
or tray across the floor conveyor).
These units can carry substantial loads so care
must be exercised to ensure that adequate truck
components, axles, springs and wheels, are
specified to carry the load. This is particularly
important on combination units that are also
equipped with snow plows.
Rearward Casting Spreaders (e.g. Zero Velocity)
With normal spreaders, a high percentage of the
dry salt applied to the road bounces off the road
due to the combination of the impact of the
granules hitting the pavement, and the speed of
the spreading vehicle. This is reduced somewhat
by pre-wetting or pre-treating materials.
Most organizations now theoretically constrain
their spreading speed to avoid wasting salt due to
the scatter effect at higher speeds. In practice
however, speeds of 40 km/hr and more are not
uncommon. If salt could be applied at higher
speeds, combination units would be much more
productive as the unit could apply salt at plowing
speeds. This would allow for safer operating
condition since trucks could move at the speed of
Casting material rearward has shown potential for
salt use reduction by increasing the percentage of
applied salt that is retained on the road, and in the
required location on the road.
Multipurpose Spreaders
Multipurpose spreaders incorporate most benefits
of the other spreaders.
They use a longitudinal conveyor to transport salt
or sand to the front of a large modern contractors
dump box.
A recent design makes use of a U-shaped box to
ensure that no material hangs up in the box and
that all material can be easily removed from the
box at the end of the shift.
April 2013
Syntheses of Best Practices
Road Salt Management
This is a concept by which the salt is discharged
rearward at exactly the same speed as the
spreading vehicle is traveling forward. The two
velocity components cancel each other causing
the salt to drop on the road as if the spreading
vehicle was standing still.
self-contained stilt legs in the maintenance yard,
and remain tarped until needed.
To-date, the available equipment has experienced
some operational problems such as material
caking, uneven discharge and mechanical
complications (fan/blower) under certain
conditions and is not in broad use.
One manufacturer makes use of a shielded-spinner
at the mid-chassis discharge location, discharging
at a point just beyond the width of the rear wheels
where the material is “flung” rearward.
Another manufacturer used a high-speed blower
to discharge the salt rearward. This results in a
large cloud of salt that can be hard to control and
may be affected by side winds.
Also, the spreader units may not suitably handle
pre-wetted material or finer sands.
Though useful for salt applications, there is no
good way to spread sand with these spreaders.
Based on the premise that no salt particle should
be placed dry onto the road surface, and that fine
salt is the gradation of choice for prompt dissolving
and melting, certain spreader design
characteristics cater better to liquid and fine salt
use in pre-wetted applications.
The salt must be of a fine gradation in order for it
to retain the brine moisture content and fine salt
does not travel as easily on certain chain-type
conveyor systems.
Increased liquid use can have detrimental effects
on equipment when the discharge location is other
than at the rear.
These spreaders allow a “high-ratio” salt
application rates up to 255 litres per tonne of salt,
or at a ratio of 30:70 liquid-to-solid by weight. This
requires a large capacity of onboard liquid and
adequate pumping capability which may not be
possible or practical on a conventional retro-fitted
In one design, an internal longitudinal agitator bar
meters salt from the hopper, while breaking down
chunks in the load, onto a belt conveyor that
moves the material to the rear-discharge location.
Calibration by weight can be done accurately off
the rear belt.
Pre-wetting liquid can be applied directly on the
spinner that is designed to spread the material
across a given area of the road cross section.
Some of these units are also configured to apply
DLA either from the spinner or using a spray bar.
Though some units are considered to be well-built,
they cost more than conventional spreaders.
One consideration is that areas that only have
access to coarser salt may find that the liquid
component must be reduced since saturation can
be achieved with less liquid.
Overall spreader designs are evolving and are
worthy of continual investigation.
Electronic Spreader Controls
Rear-discharge Spreaders
These spreaders are either frame-mounted or
slide-in rear-discharge v-hoppers that can stand on
All spreaders require an accurate electronic
controller to ensure that the appropriate
application rate is achieved.
Simple hydraulic circuits, used to maintain a
steady application rate, are still in use in many
road authorities and most private contractors
servicing parking lots. This equipment starts to
exceed the desired application rate as soon as the
truck speed drops below the design speed and an
excessive salt application is then dumped on the
Early models of the electronic controllers were not
dependable and required extensive maintenance.
The new models are improved but can still require
some patience.
Modern spreaders use electronic groundspeed
spreader controls to provide consistent, accurate
application rates. The truck speed is monitored
from the truck’s speedometer drive, and the
spreader output is adjusted to maintain a steady
output at the set rate per kilometre. Both open
loop and closed loop systems are available to
monitor material flow and provide increased
April 2013
Syntheses of Best Practices
Road Salt Management
accuracy of the spread rate (closed loop systems
provide confirmation of the actual application
Electronic controllers automatically increase the
output rate if a second spinner is actuated (if so
equipped) to treat truck climbing and turning
With some electronic units, calibration settings
can be applied electronically using infrared
Information that is captured and logged can
include: amount and type of material applied,
gate position, run time, blast information, average
speed, spread width/symmetry, etc.
operations by generating useful data or by supporting
the service delivery itself. These are discussed in the
following sections.
There is the saying – You Can’t Manage What You
Don’t Measure! Review of salt management practices
over the past 5 years shows that most road
organizations have many if not all of the tools to
properly manage their salt use but the actual salt use is
not always being optimized.
Often what is missing in salt management practices is
active tracking of salt use against targeted objectives
and a concerted effort to adjust wasteful practices.
Manufacturers can now provide units that record,
for printing, information about the amount of salt
used, the time it was used and the associated
application rate, for analysis and control by the
The following sections discuss equipment that is
available to help with this monitoring process.
Modern controllers incorporate global positioning
systems (GPS) for automated vehicle location (AVL)
and to identify where the material was discharged
(either generating a passive history or a live
It is important to know how much material should be
applied for given precipitation and pavement
temperature conditions over a given area.
Snowfighting organizations should have multiple
application rates (low, medium, high) for each
type of material they are applying that are geared
to weather and pavement conditions.
The size of the various areas to be serviced (e.g.
routes, parking lots, sidewalks, platforms etc.)
should be determined.
The amount of each material required to service
specific areas can be determined for the various
application rates by multiplying the area by the
application rate.
This benchmarking only needs to be done once and
reviewed when changes are made to the rates or
the service area.
Some road authorities print the amount of salt
needed to service an area (route or lot) on the
beat/route maps provided to the operators.
It is these benchmarks and their monitoring/
reporting system that allow organizations to
ensure that they are placing the right amount of
salt and meeting their goals.
Regardless of the spreader chosen, the service provider
must calibrate each spreader to have faith that the
application rate settings are indeed accurate. A
calibration policy should be established to assure the
material settings are correct. Preferably, if application
is by weight, then calibration should also be by weight.
All spreaders should be calibrated before the start of
the season and recorded. Calibration checks or
recalibration should take place several times during the
season, including:
after repairs to and system that can affect salt
when distribution calculations show a
discrepancy between theoretical and actual
spot-checks on units in the fleet throughout
the season
Various types of equipment support the winter
maintenance program either by helping manage the
April 2013
Syntheses of Best Practices
Road Salt Management
Loading extra material onto a spreader can lead
to overloading or the temptation to over apply the
salt. In the past, operators tended to load a little
extra salt as there was no exact method of
determining the amount of material loaded, and
they did not want to run out without completing
the route.
Pump meters at the brine loading station should
be used to measure the amount of brine delivered
to each truck in order to track loading times and
Overloaded trucks also contribute to
contamination in the area of the salt storage
facilities. Salt heaped above the side boards is
thrown off the trucks as they negotiate curves to
exit the yards.
There should be records kept of the amount of
liquid loaded onto pre-wet and DLA units as well
has how much liquid is used for each round. This
will help to confirm overall usage and proper
application rates for management and legal
It is also important to have testing methods for
confirming that liquids are at the ideal
concentration. Some liquid production units
measure concentrations on an ongoing basis
during the production process and only deliver the
completed brine to storage once the desired
concentration has been reached. Brine
concentrations should be checked using other
means to ensure that the production process is
delivering the desired product.
With electronic scale control systems operators
can more precisely load the right amount of salt.
This device is a relatively inexpensive, durable and
accurate weighing device consisting of a
transducer load cell mounted to the loader bucket
These devices can measure a predetermined load
size for the scheduled route (length of route X
application rate + a limited contingency amount
for bridge decks, intersections, etc.). In other
words the benchmarked amount for the conditions
of the event.
Models are available that will record with the
loader in motion so that the loader operation is
not impeded.
The units will record the amount loaded and can
download or print out a ticket for tracking
Liquid Meters
Automated Vehicle Location (AVL)
Though the equipment can be overridden, it
provides the operators with a mechanism to
accurately measure and control the amount of
material loaded on the spreaders.
AVL is a way of tracking equipment movements
along with the services provided using GPS
receivers/transmitters and software.
The process usually involves a third-party provider
that receives and assembles the vehicle position
data from the GPS and operational data from the
vehicle’s controller by cell phone and provides it to
the client over the internet.
Many organizations have had difficulty getting
quality data and management reports from their
third party provider. Typical issues relate to
equipment failure, operator sabotage, holes in the
cell phone coverage and software mismatches.
The electronic records can either be actively
followed real-time or can be passively recorded for
later analysis. It is also archived for future
reference in the event of an incident or for review
and management purposes. On-board data
storage help to manage transmission costs, deal
with communication gaps and ensure data
The AVL provider needs to be able to collect and
properly interpret the data from the controllers
and relay this to the client. Because all controllers
Truck Scales
Weighing the trucks as they enter and leave the
maintenance yard is a way of confirming the
amount of material loaded and how much was
spread on the serviced route.
This function can be automated with a weigh-inmotion pad that tracks the equipment movement
and can serve to reconcile the data from the
spreader controller and other documentation.
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do not use a common protocol for exchanging
data the AVL needs to provide an interface that
translates the output from each controller into
common language. A problem occurs when there
is a mismatch between the translation software
and the controller. This can happen when a
controller is changed and the translation software
is not matched to the new controller. In this case
the data is useless. Purchasers of this service
should insist that the AVL supplier has a quality
control system that can detect and report when
data issues occur. Otherwise incorrect data can be
The electronic record can either be actively
followed real-time or can be passively recorded for
later analysis. It is also archived for future
reference in the event of an incident or for review
and management purposes.
This equipment can provide operational support to
greatly enhance the monitoring of salt usage, to
demonstrate prudent usage and to correlate with
the achievement of the required level of service. It
is also useful for proving that specified services
were provided, which is useful in defending against
legal action.
Loaders used to fill spreader vehicles are often
fitted with buckets that are too large for the
spreader hopper bodies. This results in spillage.
Though they have a slower production rate,
smaller buckets are available for most loaders, or
side dumping bucket attachments can be used
which provide quick precise loading.
Bulk Material Conveyors
Salt is normally blended into stockpiled winter
sand for the main purpose of keeping the sand
free-flowing and to prevent it from freezing in the
High-ratio mixes are rarely necessary; an
exception might include anticipated periods of
rapid temperature fluctuations.
Ideally, blended winter sand stockpiles are put up
in favourable, dry conditions.
Relatively dry sand stored indoors should not
require more than 1-2% salt by weight; more
moisture in the sand may require more blended
salt (up to 5%), but the purpose still is to keep the
sand free-flowing, and not to support melt action.
Traditionally, blending took place on the apron to
the storage shed, with several buckets of sand
spread level, followed by one bucket of salt
trickled on the surface; the resulting blend was
loaded in the dome, and the process was
Bulk Salt Handling by Loaders
Extensive environmental contamination has been
identified in proximity to salt storage yards. Much
of this contamination results from poor salt
handling practices.
Conveyors are available which are designed to
allow salt trailers to dump directly into the
conveyor for movement into the storage facility.
April 2013
Pre-loaded drop-hopper loaders meter salt into
spreader trucks
- Overhead silos can be pre-filled with salt to
similarly meter salt into spreader trucks
- Pneumatic handling equipment can handle fine
material that is used for either direct
application onto the road or for blending with
Whatever equipment is used for moving salt, it
should provide a way of tracking the flow so the
quantities can be recorded and reconciled.
Sand/Salt Blend Mixers
route optimization to rationalize the number
of trucks required and thus the expected salt
to be used on the roads serviced
thermal mapping where pavement
temperatures from on-board sensors can be
related to location
automatic spreader adjustments by location
determining salt loadings on service segments
or within salt vulnerable areas
Various bulk facilities are in use as follows (and are
further described in the Design and Operation of
Road Maintenance Yards SOBP):
AVL can support a number of management needs
Syntheses of Best Practices
Road Salt Management
Though highly inefficient, it was also highly inaccurate, and produced sporadic result on the pavement surface.
Equipment to support high-production stacking
and uniform, light blends now involves a form of
dual-auger pugmill or a twin conveyor feed. In
either case, two supply lines are metered to an
accurate ratio and the final conveyor stacks the
completed mixture.
when using a 96% pure salt source per one-bucket
(2m3) or 10,000 litre brine batch. Clean-out time
should be accounted for in production rates.
Manufactured salt brine can be pumped directly
into tanks mounted on the spreaders or
transferred to holding tanks at the maintenance
Stored brine will normally stay in solution as long
as there is not evaporation or a drop in
temperature below eutectic.
Additives such as corrosion inhibitors may
complicate long-term storage, in which case
agitation or recirculation could be considered.
The following two sections discuss aspects of brine
production and delivery. Further issues on brine supply
and liquid storage are contained in the Design and
Operation of Maintenance Yards SOBP.
Brine Delivery Equipment
Brine Production Equipment
Several manufacturers offer equipment to
manufacture salt brine for pre-wetting and direct
liquid applications.
Both batch plants and higher capacity continuous
flow plants are available.
Water is added to rock salt in the batch plants to
produce a saturated brine solution.
In the continuous flow plants, normally water is
forced through salt under pressure. Solution
strength can be metered and controlled
Overhead drop-hoppers can slowly meter the salt
into the water for quicker dissolving.
In all cases, the concentration should be checked
with a hygrometer or refractometer. The
hygrometer measures the specific gravity of the
solution. The percent of saturation is determined
by reference to specific gravity charts for the
specific solution temperature. Hygrometers are
calibrated to a specific temperature and can give
different readings at different temperatures.
Refractometers may be more reliable.
Unlike brine production, no special equipment is
required for liquids that are delivered.
When liquids are purchased laboratory test data
should be provided to ensure that the
concentrations are correct for the temperatures
at which the liquid will be stored and used.
Brine that is delivered should be tested to ensure
that it meets the desired specification before it is
used or mixed with other brine.
Sampling containers and a refractometer or a
properly calibrated hygrometer should be
available for sampling and testing the
Having proper equipment and effectively using this
equipment are the most effective ways of ensuring that
the right amount of salt is placed at the right time and
in the right location. Organizations should strive to
improve their fleet as quickly as possible given their
fiscal realities.
As new equipment is phased in, priority should be given
to allocating the new equipment to Service areas
adjacent to salt vulnerable areas, and reallocating less
salt-efficient equipment to less sensitive areas.
Water supply flow rates are a critical factor.
Production sites may require cisterns that capture
surface drainage to ensure adequate water supply
where well production rates are poor.
Technologies such as the use of liquids should be
implemented as a way of reducing salt use and
improving safety.
Most salt supply specifications allow for some
insoluble contaminants in the salt. This can
amount to approximately 100kg of waste grit
April 2013
Syntheses of Best Practices
Road Salt Management
equally important, choosing not to spread when it is not
required. It is also important to choose to plow the
accumulated snow and slush, but also important to not
prematurely plow salt-laden slush before the salt has
done its job.
The data logging and reporting capabilities of loader
scales, electronic controllers and GPS/AVL systems can
assist organizations in more accurately tracking their
salt use. Progress in implementation of best salt
management practices can be measured in
improvements to the fleet and the type and quantity of
materials used. Monitoring and record keeping should
type and amount of winter materials being placed
per unit area
percentage of fleet equipped with electronic
spreader controllers
percentage of fleet equipped with pre-wetting
percentage of fleet equipped with direct liquid
percentage of fleet calibrated annually
percentage of staff trained in equipment use
To ensure operators are confident in their duties and in
using the assigned equipment, they should have
training in such equipment-related topics as:
Traditionally, equipment-related training focused on
equipment maintenance and the safe operation of the
vehicle. This was followed by specific training on the
differences between vehicles, which covered the
spreader controller features and how to change
settings, etc.
These aspects of staff training are still essential to the
safe and effective use of equipment. Further
equipment-related training, however, should also
emphasize the impact of the operator’s decisions made
along the route, the range of settings and
methodologies available to the operator and tie these
to her/his roles as a “snowfighter” and “decisionmaker.” Equipment training should be integral with
other winter maintenance topics such as the science of
salt and record keeping.
route/site familiarization (preferably during
pre-season driver training
spreader calibration (specific to those doing
“circle-check” procedures
spreader controller operation
brine equipment operation
equipment washing procedures
minor equipment repair
good housekeeping practices
record keeping
effective loader operation (specific to loader
use and interpretation of pavement sensor data
and forecasts
infrared thermometer use;
agency policies
The following equipment-related learning goals should
be included in a training program:
In the past, a plow operator could be forgiven for only
plowing, just as a spreader operator might only spread.
That was the job after all. With today’s understanding
of best practices for snow and ice control and with the
more sophisticated equipment that is available,
operators need to understand that “decision-making”
means choosing to spread when appropriate, and,
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Understand the concept of putting out the right
material, in the right amount, at the right time,
and leaving it there long enough to do the job.
Understand how the electronic controller and
gate settings on each spreader must be set to
achieve the specified application rates.
Understand how to calibrate each spreader to
ensure that the right amount of material is being
spread. The equipment should be calibrated to
multiple rates for low, medium and high
Understand how to recognize when re-calibration
is necessary.
Syntheses of Best Practices
Road Salt Management
Understand the importance of timely plowing.
Understand how to efficiently plow each beat/
route/lot/sidewalk etc.
Understand the role and effective placement of
snowdrift control devices (structural snow fences,
snow ridging, agricultural stubble, living snow
Understand how to fill spreaders and direct liquid
units with liquid chemicals.
Understand the health, safety and environmental
precautions that need to be taken when handling
liquid chemicals.
Understand how to measure brine concentrations.
Understand the components and purpose of RWIS
Understand how to properly mount a truckmounted IRT so as to avoid erroneous readings.
Understand that IRTs are for measuring
temperature trends not exact temperatures.
Understand precautions about handling and using
Understand the importance of proper record
keeping and how to complete the required
documentation on equipment maintenance and
salt use.
icing and the expanded use of liquid materials, winter
maintenance can be completed to the same or higher
standard and with a substantial reduction in salt use.
Equipment is available to facilitate more precise
controlled applications of material, at the newly
reduced rates established as a result of extensive
research and testing. This equipment is much more
sophisticated, durable and easier to use, but the
potential benefits can only be realized if maintenance
staff are thoroughly trained and material use is closely
Snowfighting activities can be tied into sensor based
information systems including real time data, forecasts,
friction measurements, surface temperature
measurements and global positioning equipment. As
the use of this technology evolves, considerable
planning, organization and evaluation are required to
ensure the best use of the equipment that is available.
A transition strategy will be required to shift to new
technologies. This changeover cannot happen
overnight, but the shift can occur strategically. For
instance, the spreaders on the highest salt routes or in
proximity to vulnerable areas could be targeted first for
replacement, and the most versatile mechanical
removal equipment could be stationed where it will
help lessen salt loadings. To gain experience in new
methodology, new equipment could be assigned to
preferred “champions” in the organization for
demonstrated use on less significant areas until there is
confidence in the new practices.
Modern snowfighting equipment used to clear snow
and ice, including snowplows and spreaders, has
improved significantly in recent years. Using new
technologies, together with implementation of anti-
Organizations should review their equipment needs and
fleet management strategy regularly, and stay current
with changes in the business.
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Syntheses of Best Practices
Road Salt Management
The development of this Salt Management Synthesis of Best Practices was undertaken with funding provided by
several agencies. TAC gratefully acknowledges the following funding partners for their contribution to the
 Alberta Transportation
 Regional Municipality of Waterloo
 British Columbia Ministry of Transportation
 Salt Institute
 City of Burlington
 Saskatchewan Highways
 City of Edmonton
 Transport Canada
 City of Moncton
Principle Consultant for update was Ecoplans, a
member of the MMM Group Limited and Bob
Hodgins (previously with Ecoplans, now an independent consultant).
 City of Ottawa
 City of Toronto
 City of Winnipeg
This document is the product of a project conducted
on behalf of the Chief Engineers Council under the
supervision of a project steering committee. TAC
thanks all the committee members who contributed
their time and effort to this project.
 Manitoba Infrastructure and Transportation
 Ministère des transports du Québec
 Ministry of Transportation Ontario
 Newfoundland Transportation
 Nova Scotia Transportation and Infrastructure
Transportation Association of Canada
2323 St. Blvd., Ottawa, Canada K1G 4J8
Tel: (613) 736-1350 ~ Fax: (613) 736-1395
 New Brunswick Transportation and Infrastructure
 Regional Municipality of Halifax
April 2013
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