The use of automobile trains and tractor-transport units with trailers helps to increase labor productivity in transport operations during the transportation of agricultural goods, and improves the efficiency of transport use. Tractor trailers compared with tractors have not improved much and, due to their technical characteristics (stability of rectilinear movement, shunting performance, etc.), do not allow to use the full-speed capabilities of modern wheeled tractors. The article discusses issues related to increasing the stability of a tractor overturning train on a bend when picking transport units with trailers whose wheels are controlled through the steering trapezoid, as well as with trailers equipped with front swivel trolleys. An updated method for determining the critical speed of a tractor train by the stability of a biaxial trailer with a rotary axis on a curved path is given. The analysis of stability and critical speed on rollover at the turn of a biaxial trailer with a rotary axle and a trailer with steered wheels through the steering trapezoid. The results of the calculated data of the critical speed for rollover using the proposed method are presented on the example of a tractor-transport unit composed of a 2-PTS-6 biaxial trailer equipped with a steering mechanism of steered wheels through the steering trapezoid and with a trailer having a rotary axle of the front wheels. The reasons for the decrease in the critical speed for capsizing trailers with a rotary axis are determined. A number of technical solutions are proposed, confirmed by patents, which make it possible to compensate for the effect of centrifugal force acting on the trailer when turning, causing it to tip over, the use of which would increase the safety of tractor trains in operating conditions.