Road accident types

Road traffic accidents generally fall into one of four common types:

* Head on Collisions
* Accidents at junctions
* Run-offs
* Accidents involving pedestrians/cyclists

Although other types of accident do occur.

Head-on Collisions

See also Head-on_collision#Road_transport.

Head-on collisions often have poor outcomes because of the speed involved when the collision takes place. On a 60mph single carriageway road with no separation of opposing lanes of traffic, the legal closing speed of two vehicles will be 120mph.

The obvious cause of head-on colissions is when one vehicle inadvertantly strays into the path of an oncomming vehicle. However, the root cause sometimes lies in a steering overcorrection after veering to the side of the road as opposed to the centre [ cite web|url=http://www.irap.net/toolkit/default.asp?p=crash&ds=1&i=10|accessdate=2008-09-26 |title=Head on Crashes|publisher=International Road Assessment Programme] .

Risk of Head-on Collisions

The likelihood of head-on collision is at its greatest on roads with no separation of lanes of opposing traffic and worsens as traffic flow increases. While the outcome worsens as speed increases.

Therefore the roads with the gratest risk of head-on collision are busy single-carriageway roads outside urban areas where speeds are highest cite web|url=http://www.eurorap.org/accidents_in_eurorap|accessdate=2008-09-26 |title=Accidents on European Roads|publisher=European Road Assessment Programme] .

Contrast this with Motorways, which rarely have a high risk of head-on collision inspite of the high speeds involved [ cite web|url=http://www.eurorap.org/mapfullscreen.asp?ID=2|accessdate=2008-09-26 |title=Great Britain Risk Rate Map|publisher=Road Safety Foundation] , because of the median separation treatments such as Wire_Rope_Safety_barriers, Concrete_step_barriers, Jersey_barriers and Metal Crash Barriers.

Countermeasures

The greatest risk reduction in terms of head-on collision comes through the separation of oncoming traffic, also known as median separation or median treatment which can reduce road accidents in the order of 70% [ cite web|url=http://prelive.eurorap.org/save_lives|accessdate=2008-09-26 |title=Practical Ways to Save Lives|publisher=European Road Assessment Programme] . Indeed both Ireland and Sweden have undertaken large programmes of safety fencing on 2+1 roads.

However the installation of median barriers can cost in excess of $100,000. Much cheaper accident reduction methods are to improve road markings, reduce speeds and to separate traffic with wide central hatching [ cite web|url=http://www.irap.net/toolkit/default.asp?p=crash&ds=1&i=10|accessdate=2008-09-26 |title=Head on Crashes|publisher=International Road Assessment Programme] .

Sealing of safety zones along the side of the road (also known as a hard-shoulder) can also reduce the risk of head-on collisions caused by steering over correction when drivers accidentally veer off the side of the road [ cite web|url=http://www.irap.net/toolkit/default.asp?p=treatment&i=70|accessdate=2008-09-26 |title=Shoulder Sealing|publisher=International Road Assessment Programme] .

Intersection Accidents

Crashes at intersections (road junctions) are a very common type of road accident types. Accidents may involve head-on impact when one vehicle crosses an opposing lane of traffic to turn at an intersection, or side impacts when one vehicle crosses the path of an adjoining vehicle at an intersection.

Risk of Intersection Accidents

The risk of intersection accidents differs on rural and urban roads, with around 50% of urban crashes and 30% of rural crashes occurring at junctions [cite web|url=http://safety.transportation.org/doc/1P%20Unsignalized%20Intersection%20Crashes.pdf |accessdate=2008-09-26 |title=A Guide for Addressing Unsignalized Intersection Collisions|publisher=National Cooperative Highway Research Program] . In urban areas the likelihood of an intersection accident occuring is high as they typically have a higher density of junctions. On rural roads while the likelihood of an accident may be lower (because of fewer intersections) the outcome of the accident is often significantly worse because of the increased speeds involved [ cite web|url=http://www.irap.net/toolkit/default.asp?p=crash&ds=1&i=27 |accessdate=2008-09-26 |title=Intersection Accidents|publisher=International Road Assessment Programme] .

Because intersection accidents often result in side-impacts they are therefore often fatal because people are seated close to the part of the car that provides little protection.

Countermeasures

Although expensive to implement roundabouts are an effective way of reducing the speed of traffic at intersections reducing the likelihood of high speed right-angle collissions [ cite web|url=http://www.irap.net/toolkit/default.asp?p=treatment&i=75|accessdate=2008-09-26 |title=Intersection - Roundabouts|publisher=International Road Assessment Programme] . Clear road markings and signing are low cost methods of improving safety at intersections [ cite web|url=http://www.irap.net/toolkit/default.asp?p=treatment&i=82|accessdate=2008-09-26 |title=Intersection - Delineation|publisher=International Road Assessment Programme] ..

References

External Links

* [http://www.irap.net/toolkit/default.asp?p=crash&ds=1&i=27 iRAP Road Safety Toolkit - Intersection Crashes]
* [http://www.rta.nsw.gov.au/licensing/tests/hazardperceptiontest/novicedriversareatrisk/5mostcommoncrashtypes.html Illustrations of Intersection Accident]
* [http://www.rta.nsw.gov.au/licensing/tests/hazardperceptiontest/novicedriversareatrisk/5mostcommoncrashtypes.html NSW Government - 5 most common crash types]
* [http://www.eurorap.org/accidents_in_eurorap Accidents on European Roads]