An 80,000 pound semi truck isn’t a sports car. It’s designed to haul freight while handling is a secondary consideration. This leaves truck drivers with few options in emergency situations. They can hit the brakes and possibly not stop in time, or swerve and possibly rollover or jackknife their rigs. In spite of these handicaps, some truck drivers depower the brakes on their tractor and rely solely on the trailer brakes for braking action.
Why would they risk their lives and safety this way? To save money. This unsafe practice is illegal and probably isn’t done by the reputable trucking companies. They have too much to lose by engaging in such a practice. Instead, it’s the small owner operator who is most likely to do this. It is especially tempting when the owner operator is contracted by a trucking company to haul their trailers.
The owner operator hooks his tractor to the client’s trailer and hauls it to its destination. By depowering his tractor’s brakes, he can avoid wear and tear on his tractor’s brakes and tires. At this point he relies solely on the trailer brakes, which belong to his client the trucking company. Trailer brake maintenance is, of course, paid for by the trucking company.
This practice reduces the number of brakes used for slowing down the rig, which increases its stopping distance. It also increases the risk of jackknifing. The owner operator, if he chooses to do so, tries to cope by increasing his following distances. However, he is also taking a risk at the expense of the driving public.