Head-on collision

A head-on collision is a traffic collision where the front ends of two vehicles such as cars, trains, ships or planes hit each other in opposite directions, as opposed to a side collision or rear-end collision.

With railways, a head-on collision occurs most often on a single line railway. This usually means that at least one of the trains has passed a signal at danger, or that a signalman has made a major error. Head-on collisions may also occur at junctions, for similar reasons. In the early days of railroading in the United States, such collisions were quite common and gave to the rise of the term "Cornfield Meet." As time progressed and signalling became more standardized, such accidents became less frequent. Even so, the term still sees some usage in the industry. The origins of the term are not well known, but it is attributed to accidents happening in rural America where farming and cornfields were common. The first known usage of the term was in the mid-19th century.

The distance required for a train to stop is usually greater than the distance that can be seen before the next blind curve, which is why signals and safeworking systems are so important.

Note: if the collision occurs at a station or junction, or trains are traveling in the same direction, then the collision is not a pure head-on collision.

With shipping, there are two main factors influencing the chance of a head-on collision. Firstly, even with radar and radio, it is difficult to tell what course the opposing ships are following. Secondly, big ships have so much momentum that it is very hard to change course at the last moment.

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 U.S. 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., except for the case of a lighter car colliding with a heavier one. The television show MythBusters performed a demonstration of this effect in a 2010 show.

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