Head-on Collision - Road Transport

Road Transport

Head-on collisions are an often fatal type of road traffic collision. U.S. statistics show that in 2005, head-on crashes were only 2.0% of all crashes, yet accounted for 10.1% of US fatal crashes. A common misconception is that this over-representation is because the relative velocity of vehicles traveling in opposite directions is high. While it is true (via Galilean relativity) that a head-on crash between two vehicles traveling at 50 mph is equivalent to a moving vehicle running into a stationary one at 100 mph, it is clear from basic Newtonian Physics that if the stationary vehicle is replaced with a solid wall or other stationary near-immovable object such as a bridge abutment, then the equivalent collision is one in which the moving vehicle is only traveling at 50 mph. The television show MythBusters performed a demonstration of this effect in a 2010 show.

Head-on collisions, sideswipes, and run-off-road crashes all belong to a category of crashes called lane-departure or road-departure crashes. This is because they have similar causes, if different consequences. The driver of a vehicle fails to stay centered in their lane, and either leaves the roadway, or crosses the centerline, possibly resulting in a head-on or sideswipe collision, or, if the vehicle avoids oncoming traffic, a run-off-road crash on the far side of the road.

Preventive measures include traffic signs and road surface markings to help guide drivers through curves, as well as separating opposing lanes of traffic with wide central reservation (or median) and median barriers to prevent crossover incidents. Median barriers are physical barriers between the lanes of traffic, such as concrete barriers or cable barriers. These are actually roadside hazards in their own right, but on high speed roads, the severity of a collision with a median barrier is usually lower than the severity of a head-on crash.

The European Road Assessment Programme's Road Protection Score (RPS) is based on a schedule of detailed road design elements that correspond to each of the four main crash types, including head-on collisions. The Head-on Crash element of the RPS measures how well traffic lanes are separated. Motorways generally have crash protection features in harmony with the high speeds allowed. The Star Rating results show that motorways generally score well with a typical 4-star rating even though their permitted speeds are the highest on the network. But results from Star Rating research in Britain, Germany, the Netherlands and Sweden have shown that there is a pressing need to find better median (central reservation), run-off and junction protection at reasonable cost on single carriageway roads.

Another form of head-on crash is the wrong-way entry crash, where a driver on a surface road turns onto an off-ramp from a motorway or freeway, instead of the on-ramp. They can also happen on divided arterials if a driver turns into the wrong side of the road. Considerable importance is placed on designing ramp terminals and intersections to prevent these incidents. This often takes to form of special signage at freeway off-ramps to discourage drivers from going the wrong way. The Manual on Uniform Traffic Control Devices provides instruction on this signage installation in its Section 2E.50.