In the nation of Partoria, large trucks currently have a much higher rate of traffic accidents per mile driven than other vehicles do  However, the very largest trucks-those with three trailers-had less than a third of the accident rate of single- and double-trailer trucks
Clearly, ttherefore, one way for Partoria to reduce the number of traffic accidents would be to require shippers to increase their use of triple-trailer trucks
Partorian trucking companies currently use triple-trailer trucks only for long trips using major highways, which is the safest kind of trip for large trucks.