The first problem contributing to rollovers is that trucks are more top heavy, and therefore are more likely to tip over. A typical tractor-trailer tips over about three times more readily than a car during a steady turn at an intersection. Some trucks are even worse. For example, Ontario allows single semitrailers that are even more top heavy and inclined to tip over than tractor-trailers at recommend loadings. Tanker trucks are at increased risk of rollover, because the load can shift.
Tankers can also carry hazardous goods that can spill.
This problem is even worse in Ontario, where certain types of tankers are allowed to be loaded more heavily. The second problem occurs at higher speeds when a double or triple trailer truck has to swerve to avoid something on the road. The tractor can make the move, but the rear trailer suffers a crack the whip force that make it skid into other lanes or rollover. The more trailers there are, and the more hitching points between trailers, the more likely it is the rear trailer will tip over. New Trucks Federal Transport Minister David Collenette announced on Feb 9 that ABS brakes will be required on new big trucks as of December, 1999.