Depending on whether a driver follows long-haul or local routes, state and federal rules regulate licensing, training, hours on the road per day, log books, and even the safety equipment on the vehicle. Also, many commercial trucking incidents need to be reported to the department of transportation which can demonstrate a history of unsafe practices by a particular driver or company. Many of these records can be destroyed after six months. Contact an experienced commercial trucking lawyer right away so that the evidence you need in your case will be preserved.