A rural roadway departure is defined by the Federal Highway Administration (FHWA) as when a vehicle crosses the edge line or centerline or otherwise leaves the traveled way in a rural area. These departures are deadly, taking an average of 12,000 lives each year.
These staggeringly high numbers are due to several factors that increase rural roadway departures, such as distracted driving, less lighting and higher driving speeds.
Many countermeasures for rural roadway departures are placed on the road’s surface. Here are five of the most common and effective.
HIGH FRICTION SURFACE TREATMENTS (HFST)
Frequent, heavy braking at roadway curves can prematurely polish the pavement, reducing the friction necessary to help drivers maintain control of their vehicles, especially in wet conditions. In fact, research from the National Transportation Safety Board and FHWA shows approximately 70 percent of crashes on wet pavement can be prevented or minimized with better pavement friction.
Fortunately, high friction surface treatments (HFST) are specifically designed to restore or maintain that friction. HFST is a polish-resistant and abrasion-resistant aggregate added to a roadway via a polymer binder — and it can be applied in mere hours. On top of having little environmental impact, treatments can often last over a decade.
The Pennsylvania Department of Transportation (PennDOT) has installed HFST at more than 400 locations, and an analysis of 15 sites found that the treatment saved an average of one life per year. Costing $262,000 to install, the treatment saved PennDOT $5 million dollars, likely due to less first responder and maintenance crew resources being needed.
EDGE LINES AND CENTERLINES
Many rural roads lack edge lines and centerlines, but adding them to all major rural roadways, as well as minor ones with a history of crashes, can significantly increase safety.
A ten-state, 500-site study conducted by the FHWA found that adding edge lines and centerlines on rural two-lane highways reduced crashes by 36 percent. In addition, adding edge lines to areas with existing centerlines reduced crashes by eight percent.
If existing lines are narrow, widening them to six inches can be effective. According to the FHWA, a study found that “6-inch markings have a statistically significant improvement over 4-inch markings for detection distances among both older and younger drivers under dry conditions at night.”
Another road-marking improvement is to maximize line visibility with retroreflective paint.
Because they produce a noise and vibration when driven over, edge line and shoulder rumble strips are ideal for reducing run-off-the-road crashes.
On rural, two-lane roads, shoulder rumble strip implementation was shown to reduce crash frequency by 36 percent, according to a National Cooperative Highway Research Program (NCHRP) report.
If the shoulder is narrow, the rumble strip can simply be layered over the edge line.
When a vehicle begins to leave the road, the height and slope of the pavement’s edge impacts how easily the driver can get back on. Standard pavement edges are nearly vertical, which makes it difficult for drivers to reenter the roadway without losing control of their vehicle.
In fact, pavement edges may have contributed to as many as 18 percent of rural roadway departure crashes in the U.S. from 2002 to 2004.
To reduce this problem, the FHWA’s Safety Edge initiative encourages state and local agencies to slope roadway edges downward at a 30-degree angle, a simple and inexpensive change that is especially helpful for smaller vehicles.
Faded pavement markings pose a major safety hazard – on top of being time-consuming and costly to fix – and are all too common in rural areas. Thermoplastic pavement marking paints, on the other hand, are designed to last.
Made of thermoplastic material, these paints are often formulated to withstand region-specific temperatures. They also feature glass beads that maximize paint reflectivity.
Despite a high initial cost, thermoplastic paint can be less expensive over time because of its superior durability and lifespan.
These five on-road countermeasures are effective options for reducing rural roadway departures in various regions. Their impact on rural roadway safety is backed by strong statistics and impressive data, driving home that they are key countermeasures worth the investment.
TAPCO | Senior Product Manager
With several years of product and project management experience, Nick is an expert on wrong-way solutions, dynamic curve warning systems, intersection conflict warning systems, overheight warning systems and LED-enhanced signs.
He manages product life cycles from inception to realization and compiles traffic safety market research to drive innovative ITS solutions.