A March 7, 2008 collision in Chattanooga reminds me again of how important it is to hire a lawyer early in collisions involving tractor trailers. In this wreck, according to the Chattanooga Times Free Press article on page B3, "The driver of one of the semi (sic) lost control of his truck… The truck jackknifed and hit another 18-wheeler, and three cars were caught between the trucks…"
The speed of the semi can be determined by downloading the black box computer which records sudden braking events. This data can be deleted if not downloaded promptly by a proper expert.
Driver logs, which might show the driver fell asleep at the wheel after driving more hours than the law allows, may be destroyed after six months.
The roadway marks that will show driver actions, as well as the sequence of events, start to fade and you may have other marks from other vehicles placed on the roadway.
So what would cause a driver of an 18 wheeler to loose control and jackknife?
Jackknifing means the accidental folding of an articulated vehicle (i.e. one towing a trailer) such that it resembles the acute angle of a folding pocket knife. If a vehicle towing a trailer skids, the trailer can push it from behind until it spins round and faces backwards. This may be caused by equipment failure, improper braking, or adverse road conditions such as an icy road surface.
By far the most common skid is caused when the rear wheels lose traction through excessive braking or acceleration. Skids caused by acceleration can usually be stopped by the driver taking his foot off the accelerator. If the rear drive wheels lock due to excessive braking they will have less traction than freely rolling wheels. The rear wheels then move sideways in an attempt to "catch up" with the front wheels, allowing the trailer to push the towing vehicle sideways, causing the jackknife.