According to a 2007 Large Truck Crash Causation Study released by the Federal Motor Carrier Safety Administration, truckers who were driving too fast for road conditions were an associated factor in 23% of crashes.

Nevertheless, FMCSA regulations (49 C.F.R. § 392.14) require truck drivers to use “extreme caution” in hazardous conditions.  In addition, many state commercial driver’s licenses require truck drivers to slow down by as much as a third during rain or other poor weather conditions.

Good cause existsts for mandating that semi drivers slow down in bad weather: It takes much longer to stop an 18-wheeler. Cars weigh an average of 3,500 pounds, while large commercial trucks (known as semis, eighteen wheelers, and tractor-trailers) can weigh up to 80,000 pounds with full loads. Drivers and passengers in cars can suffer severe injuries when they collide with large trucks because of that weight difference. In car-truck collisions, 98% of the fatalities were persons in a car.