Applications and Innovations
By Tina Grady Barbaccia
Back in the late 1960s, the Alexandria, Va.-based Salt Institute started a program called “Sensible Salting,” which was based on applying the minimum amount of salt or other proper deicing/anti-icing material at the right time. “You need to have an objective measure of what’s important to you in whatever material you use,” Salt Institute President Emeritus Dick Hanneman tells Better Roads.
Hanneman says to achieve this, it’s crucial to get plow operators involved. “If you only educate the manager and don’t educate the people on the truck – the people actually pushing the buttons – it’s unlikely to be very successful,” he says. “More than just the managers need to understand the [salting and deicing] program.”
Highways are the arteries linking our economy and our society, but only if they are open and safe. “Driving in a snowstorm increases a driver’s risk of a crash far more than driving impaired by alcohol or drugs,” according to the Salt Institute’s website. “We need to operate our roads so that would-be highway users can be assured that they and their cargos can arrive safely within a predictable window of time. Snow and ice contribute to congestion and traffic crashes. Winter weather congestion affects 70 percent of U.S. roadways.”
However, the standard definition of sustainability doesn’t really help when it comes to how often you should plow and how much salt you should use, adds Wilf Nixon, a professor of civil and environmental engineering at the University of Iowa.
“We need something that is more inclusive and more precise, if we are really going to make sensible winter maintenance decisions,” Nixon says. “Sustainability is typically defined as meeting the needs of the present without compromising the ability of future generations to meet their own needs. Sadly, this is rather imprecise,” he says. “It does not tell us whether a given activity is sustainable, or how we can develop a sustainable winter maintenance program.”
What Is Your Level of Service (LOS)?
The Winter Service Committee of the World Road Association (also known as PIARC) has been examining how to bring sustainability into the winter maintenance process, Nixon says. “The approach is that sustainability lies at the intersection of three areas of interest: societal, economic and environmental,” he says. “They represent this by three overlapping circles, each of which represents one of the areas of interest [similar to a Venn Diagram]. The area in which all three circles overlap represents a sustainable balance of the three interests of driving forces.”
Nixon says that the point is “that we come up with sensible decisions good for safety and mobility on the highway and the environment. Good environmental maintenance is good environmental stewardship.”
These decisions often depend on societal expectations, which can change over time, Nixon says. “What do people in the area you are serving expect from winter maintenance that you do?” For example, Nixon says, a farming community might be quite comfortable with snow on the roads and may not see a need for bare and wet pavements. “If they all have four-wheel-drive cars, completely clear roads aren’t a concern,” he says. But if it’s an urban environment, bare and wet pavements may be the expectation.
These expectations, known as level of service (LOS), can change over time, Nixon says. “Maybe folks who used to live in the ‘burbs think it might be nice to get a place out in the country,” he says. “But they are very surprised when they have snow and ice as part of a daily commute when they aren’t used to it. Should that be what drives what we do, or should we simply say, ‘You moved to the country, live with it.’?
“These are sorts of questions we need to be asking,” Nixon continues. “If we don’t ask them, we’ll be saying there is a one-size-fits-all solution. We have to be much more flexible than that. What works for a city in Iowa might be completely inappropriate for an urban county in Washington state.”
There are several ways (singularly and in combination) highway agencies characterize the LOS they provide. These include the level of effort, priority of treatment, types of treatments and results in terms of pavement conditions at various points in time during and after snow and ice events, according to the National Cooperative Highway Research Program (NCHRP) Report 526 “Snow and Ice Control: Guidelines for Materials and Methods” (http://www.onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_526.pdf).
The level of effort category includes assigning more people and equipment to higher priority routes, providing more or less effort during certain time frames, and varying the number of people and equipment providing treatment in relationship to the predicted severity of the event, according to the NCHRP report. “The priority of treatment category includes giving first and/or more frequent treatment to higher traffic routes, high-accident/problem locations, commercial/business locations, school bus routes, transit routes, health facilities, firehouse locations and schools,” the report notes. Some highway agencies use a system of providing treatment on a highway priority basis whereby the next lower category of highway is not treated until higher category roads are in “satisfactory” condition, according to NCHRP Report 526.
“A good way to define LOS is in terms of results at various points in time,” the report notes. Examples include maximum accumulation of snow on highways during a storm, absence of pack or bond during a storm, bare/wet pavement (x) hours after end-of-event, plowed and sanded (x) hours after end-of-event, friction number > (y) (x) hours after end-of-event, road plowed and road passable, according to the report.
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