Demand for road salt could be reduced if we found alternate ways to improve winter driving safety. One obvious way is to reduce winter driving speeds. Surveys show that the typical driver understands reducing speed improves safety, yet they are unwilling to reduce speed.
Winter speed limits are becoming standard practice on some highways in northern states, and dynamic message signs are a means to achieve this. The signs flash speed limits, that change in response to weather.
Statistics show that during winter, accident rates do go up. But not all accidents in winter are due to icy roads. Many of these accidents would have occurred anyway, without snow on the roads. So, there's a tendency for the public to believe that all accidents in winter are due to ice. This creates an unreasonably high demand for salt.
The demand for salt can be managed by opinion surveys, public education, and the promotion of alternate pathways to winter highway safety--such as reduced speed limits and a requirement for snow tires.
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The ideas above come from A Low-salt diet for Ontario's Roads and Rivers. I've quoted that report below.
Winter speed limits are becoming a standard practice in areas where winter driving conditions lead to increased accident rates.
Finland has established regulation mandating reduced winter speed limits on express motorways from 120 kilometres per hour (km/h) to 100 km/h and on secondary roads to from 100 km/h to 80 km/h. These winter limits allow for reduced service levels of roads that reflect a lower accident incidence. This is another shift in social responsibility for driving habits relative to weather and road conditions.
The Washington State Department of Transportation implemented a system of Dynamic Message Signs (DMS) for a variable speed to counter a significant increase in winter season accidents on Interstate 90 through the Cascade Mountains Snoqualmie Pass. Utilizing a comprehensive road weather information system, the state varies speed limits depending on the weather conditions.
Although it makes sense to consider reducing speed on highways when road conditions are less than ideal, there is no social expectation to reduce speed in winter. More to the point, the goal of winter roads maintenance is to maintain conditions such that speeds themselves can be maintained.
However, as the Estonian Road Administration points out, drivers are less than enthusiastic about cutting their speed even when they recognize the safety advantages.Ontario research correlating accidents and weather states that, “…snow events are associated with disproportionately more single-vehicle crashes; more collisions at locations without traffic controls and on roads with speed limits of 60 km/h or higher; and they are less likely to involve a turning manoeuvre than ‘normal’ driving.” The predominance of single vehicle crashes is attributed to speed.
The same work notes that seven percent of all injury collisions are attributable to weather with 21 percent of injury collisions occurring during inclement weather. It states that the relative risk ratio for injury during inclement weather is approximately 1.5. Therefore two in three injuries would likely have occurred even in good weather; one in three can be attributable to the weather. The total health costs associated with road collisions are approximately $10 billion with weather related injuries costing $700 million. Property damage on the other hand is higher with approximately 25 percent of property damage collisions occurring during inclement weather. One-half of property damage collisions would likely have occurred even in good weather; the other half can be attributable to weather. The total property damage associated with collisions in Canada is approximately $3.5 billion ($1.25 billion in Ontario; Ontario accounts for 35 percent of collisions in Canada). Twelve percent of $3.5 billion is approximately $400 million. The combined cost estimate is $1.1 billion.
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