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Roadway departure
A roadway departure (also called roadway excursion or run-off-road collision) is a type of incident that occurs when a vehicle leaves the roadway. Such incidents can lead to a single-vehicle collision.
Contributing factors can include:
If the vehicle strikes a fixed object (an object that will move very little when struck, such as a tree, bridge structure or utility pole) or rolls over, the crash is likely to result in injuries or fatalities. US statistics for 2005 show that roadway departure crashes resulted in 31% of fatal crashes, but were only 16% of all crashes. Roadway departure collisions where the vehicle is sliding or spinning and runs broadside into a fixed obstacle are particularly dangerous since the vehicle doors and sides provide less protection to occupants than the front of the car.
Target fixation is an issue for drivers, causing them to impact with objects that could be easily avoided.
An important concept in understanding roadway departure is the clear zone. This is the roadside area that is free of obstacles and dangerous slopes. Early research at the General Motors Proving Grounds found that 80% of their test drivers stopped or regained vehicle control within 30 feet (9 m) of the edge of the travel lane. As a result, civil engineers began to try to provide thirty feet of clear, flat ground next to rural highways. The result was fewer crashes. Current guidance adjusts the desired clear zone width for curvature, roadside slope, speed and volume. More width is recommended on the outsides of curves, where the ground slopes down away from the road, and on high-speed, high-volume roads.
There are several ways to reduce the consequences of roadway departure collisions. They fall into three main categories: preventing excursion incidents, minimizing the likelihood of a crash or roll-over if the vehicle travels off the shoulder, and reducing the severity of those that do occur.
Roadway cross section improvements include high-friction overlays, improving curve banking, and widening shoulders or travel lanes. The intention is to help the driver to keep the car on the roadway. They are usually expensive unless included in a highway reconstruction project.
A relatively inexpensive countermeasure is the placement of a Safety Edge—a 30° compacted taper on the edge of the pavement. This helps any driver that runs off the edge of the roadway to maintain control while trying to steer back onto the pavement. A vertical edge drop-off often results in overcorrection, leading to a head-on collision, rollover, or a run-off-road collision on the far side of the road. Pavement edge drop-offs are problematic on roads where the hard shoulder is narrow or nonexistent. The safety edge adds about 1% to the pavement costs while building or resurfacing a road.
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Roadway departure AI simulator
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Roadway departure
A roadway departure (also called roadway excursion or run-off-road collision) is a type of incident that occurs when a vehicle leaves the roadway. Such incidents can lead to a single-vehicle collision.
Contributing factors can include:
If the vehicle strikes a fixed object (an object that will move very little when struck, such as a tree, bridge structure or utility pole) or rolls over, the crash is likely to result in injuries or fatalities. US statistics for 2005 show that roadway departure crashes resulted in 31% of fatal crashes, but were only 16% of all crashes. Roadway departure collisions where the vehicle is sliding or spinning and runs broadside into a fixed obstacle are particularly dangerous since the vehicle doors and sides provide less protection to occupants than the front of the car.
Target fixation is an issue for drivers, causing them to impact with objects that could be easily avoided.
An important concept in understanding roadway departure is the clear zone. This is the roadside area that is free of obstacles and dangerous slopes. Early research at the General Motors Proving Grounds found that 80% of their test drivers stopped or regained vehicle control within 30 feet (9 m) of the edge of the travel lane. As a result, civil engineers began to try to provide thirty feet of clear, flat ground next to rural highways. The result was fewer crashes. Current guidance adjusts the desired clear zone width for curvature, roadside slope, speed and volume. More width is recommended on the outsides of curves, where the ground slopes down away from the road, and on high-speed, high-volume roads.
There are several ways to reduce the consequences of roadway departure collisions. They fall into three main categories: preventing excursion incidents, minimizing the likelihood of a crash or roll-over if the vehicle travels off the shoulder, and reducing the severity of those that do occur.
Roadway cross section improvements include high-friction overlays, improving curve banking, and widening shoulders or travel lanes. The intention is to help the driver to keep the car on the roadway. They are usually expensive unless included in a highway reconstruction project.
A relatively inexpensive countermeasure is the placement of a Safety Edge—a 30° compacted taper on the edge of the pavement. This helps any driver that runs off the edge of the roadway to maintain control while trying to steer back onto the pavement. A vertical edge drop-off often results in overcorrection, leading to a head-on collision, rollover, or a run-off-road collision on the far side of the road. Pavement edge drop-offs are problematic on roads where the hard shoulder is narrow or nonexistent. The safety edge adds about 1% to the pavement costs while building or resurfacing a road.