We’re talking road salt.

Of course nobody likes salt residue on the car or garage floor, including the folks who spread salt on highways.

But the job of the Idaho Transportation Department is to clear snow and ice for the traveling public, and salt has proven to be the best alternative.

Salt clears roads quickly and economically. Unlike sand or other grit, it melts ice; salt does not have to be swept up each spring like sand.

Salt is environmentally safe. Concentrations of salt in surface and underground water bodies along state highways do not reach thresholds dangerous to humans, wildlife or plants. Sand, on the other hand, has been shown to choke fish-spawning beds, killing fish eggs and reduces air quality when kicked up by motorists.

Sand provides temporary traction, but salt provides permanent traction by exposing bare pavement. Salt melts snow and ice by lowering the freezing point.

The amount of road salt used in Idaho is still well below the amount used in eastern states. Most of these states have used large quantities of road salt for decades. Drivers simply hit the car wash every so often to limit corrosion, which is the primary disadvantage of road salt.

Transportation department crews started spraying salt brine on roads in advance of storms last year to help break up snow floors. The brine dries as white streaks or lines on the roadway. Applying salt in this way minimizes the length of time travelers have to drive on snow by preventing it from sticking to the pavement. Snowplows can then peel the snow off more readily.

To minimize salt buildup, the transportation department strives to apply needed amounts to clear roads and no more. The goal is to keep roads wet. Applying too little salt brine or granular salt invites melted snow and ice to refreeze. Applying adequate concentrations of salt to an already wet road prevents freezing down to -7°F.

Depending on the snowstorm, location and conditions, maintenance crews previously used various combinations of grit and salt to clear roads. They plowed and sanded, as needed. Now crews use mostly straight salt and brine.

Spreading precise amounts of salt at the right time is challenging, because storms can be unpredictable and road conditions vary. Meanwhile, striking a balance between the benefits (reduced slide-offs and crashes) and costs (vehicle and concrete corrosion) of salt usage is elusive, and not everyone agrees on what constitutes balance.

Sand-salt mixtures still work as road treatments and will continue to be used under certain conditions. Options must be available to meet changing weather developments and road surfaces.

The transportation department will continue to study application effectiveness for all traditional and innovative road treatments, since these treatments work differently under diverse circumstances.

Officials are in the process of identifying optimum timing and concentration of applications in general. The transportation department is conducting a three‑part study on salt usage and other winter operations to be completed in 2015.

Ultimately, the department wants to minimize corrosion impacts while maintaining highway safety, mobility and economic opportunity for all travelers. Officials constantly seek to improve the department’s snow- and ice-control programs.

The advantages of road salt outweigh its disadvantages. Reducing slide-offs and crashes saves lives and otherwise spares people from serious bodily injury and property loss. When considered in that light, using salt over other alternatives appears to be the best choice.


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