Abstract: A new and improved anti-jackknife apparatus for tractor to trailer connections includes a fifth wheel assembly connected to a tractor and a pair of locking pin assemblies connected to the fifth wheel assembly. Each of the locking pin assemblies includes an extensible and retractable lock pin. A control assembly is connected to the pair of locking pin assemblies. The control assembly is capable of being controlled by a first control signal in response to actuation of tractor brakes and is capable of being controlled by a second control signal in response to manual actuation of a bypass switch assembly by a tractor driver. A plate is connected to a trailer such that the trailer plate encircles a kingpin extending downward from the trailer. The trailer plate includes a pair of partially-ring-shaped slots adapted to receive the lock pins of the locking pin assemblies when the lock pins are in an extended position.