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Crossing the line has consequences

Brent Jennings
Highway Safety Manager

As hard as it is to believe, at times while growing up I would exhibit bad behavior. My mother would remind me if "I crossed the line, the consequences would not be pleasant." No truer words were ever spoken!

Lane-departure crashes (crossing the line) contribute to almost half of the total economic cost of crashes in Idaho. This includes run-off-the-road and head-on crashes (the most severe types of crash). Crossing the painted line on the pavement can result in severe consequences. As we rummage around in our highway safety improvement tool box, solutions are sought in the worlds of education, enforcement, and engineering to help "maintain the lane." If the lane cannot be maintained, then unfortunately the fourth "E" or emergency medical services might need to be employed to help save lives.

So as we peak inside our "4E" tool box, one engineering solution to help maintain the lane is installation of rumble strips along the edge and, in some cases, the centerline of pavements. Over the last decade, Idaho has routinely placed rumble strips along roadway shoulders and along centerlines on the state highway system. I want to share some information that ITD's Ted Mason helped gather for me. Thanks Ted.

An analysis of Idaho's crash data from 2008 to 2012 showed that single-vehicle run-off-the-road (SVROR) crashes are one of the leading types of crashes causing fatal or serious injuries on Idaho's roadways. SVROR crashes have contributed to more than half (51 percent) of the fatal crashes in Idaho. Of those 470 fatal crashes during this time period, 416, or 89 percent, were on rural roads. One-third of the serious injury crashes are SVROR crashes. Of the 1,809 serious injury crashes, 1,436, or 79 percent, were on rural roads. National studies have shown that rumble strips and stripes can decrease these types of crashes 20 percent to 35 percent. This is also proven to be true in Idaho.

According to Ted, in 2012 our highway safety partners at the University of Idaho studied the installation of shoulder rumble strips on 2-lane rural highways. Dr. Ahmed Abdel-Rahim and his team found a 15-percent reduction in all SVROR crashes and a 74-percent reduction in severe SVROR crashes. In the case of rural freeways, the percent reduction in all SVROR crashes and severe ROR crashes was 29 percent and 67 percent, respectively.

Ted also found the focus of these rumble strip applications has been on wider shoulder areas such as found on the interstate and rural arterial highways, leaving many of the narrow shoulder areas (2 to 6 foot) with no rumble strips or with centerline rumble strips in only double yellow areas on curves. As part of a continuing safety improvement effort to further eliminate fatal and serious-injury crashes caused by drivers running off the road within these narrow shoulder areas, edgeline rumble stripes are being recommended as a low-cost roadside treatment that can yield high returns on safety.

There is a difference between the rumble strips on the interstate and the rumble stripes that are being proposed for two-lane roadways. The smaller stripes run under the painted edgeline (which actually make the edgeline easier to see at night and in wet pavement conditions). The narrower width and more shallow depth of the rumble stripe also create less noise when driven over by vehicles – enough to wake the driver but not so much to be as disruptive to people living along the state route.

This engineering solution will help drivers maintain the lane and help all of us from crossing the line. This "E" strategy, coupled with the "E" strategies of enforcement and education will help us reduce lane-departure crashes, which in-turn helps us move Towards Zero Deaths in Idaho.