The problem of ensuring road safety is of crucial importance when operating transport in road conditions. Road safety largely depends on the active and passive safety of vehicles, road infrastructure, and driver qualifications. The design of the car and road train (AP) must, first of all, meet the requirements of active safety, which reduces the likelihood of an accident. Automobile trains are among the most dangerous vehicles in terms of active safety compared to single vehicles. This is largely due to their large weight and size parameters, the presence of articulated links between the links (tractor and trailer), which in turn worsens such performance indicators that affect safety, such as maneuverability and handling, as well as the stability of the trajectory of the trailer links as a result of transverse vibrations (wagging trailers). The article deals with issues related to the influence of variable-length and adjustable-length traction devices of a single-axle trailer on the operational properties and safety of a road train. The method of determining the main kinematic parameters of the traction coupling device, which can be applied at the pre-design stage of the design of traction coupling devices and when completing tractor trains with single-axle trailers, is clarified.