42 and 44 are attached to the dolly 10 and the stabilizer bars 42 and 44 are longer than the length of the tongue 28 this connection precludes rotation of the dolly 10 about the vertical yaw axis while allowing rotation about the longitudinal roll axis and the transverse pitch axis consequently jack knifing of the dolly 10 is precluded also extreme pitching movement such as would allow the towing vehicle to flip backward in top of the trailer is precluded by the fact that the attaching points 46 of the stabilizer bars 42 and 44 with the towing vehicle 34 are not on a common line with the attaching point 32 of the tongue 28 as clearly seen in fig4 in use the user connects the trailer dolly 10 to the towing vehicle 34 by means of coupling means 32 and connects the trailer not shown to either the fifth wheel 22 or to the ball mounts 26 and 27 as appropriate in this way the trailer dolly 10 bears the weight of the trailer rather than the towing vehicle 34 also the trailer dolly 10 enables the towing vehicle 34 to be connected to the trailer regardless of which type of connection the trailer has stabilizer bars 42 and 44 are connected between the trailer dolly 10 and the towing vehicle 34 to preclude yawing of the trailer dolly 10 with respect to the towing vehicle 34 while the hydraulic system of fig5 ensures precise tracking of the dolly 10 with the.