The article presents the results of simulation calculations of the braking process in a straight-line motion of a set of a two-axle vehicle and a single-axle unbraked trailer. The stopping distance of the set on a horizontal and sloping road surface, dry and wet, was assessed. The longitudinal inclination of the road was changed, as well as the weight of the trailer and the longitudinal and vertical position of its centre of mass. The result of the work is a qualitative and quantitative assessment of the impact (on braking efficiency) of attaching an unbraked single-axle trailer to a two-axle car when going up and down a hill and on a level road surface. The obtained results showed that the additional load of the vehicle itself (without the trailer) had no effect on the length of the stopping distance or on the value of the maximum braking deceleration when the driver could fully use the traction of the road wheels to the road surface. Attaching an unbraked trailer has the greatest effect on the lightest vehicle. As expected, positive elevation shortens the stopping distance, while negative elevation lengthens it. The length of the stopping distance increases significantly on a wet surface, which is particularly noticeable for negative elevation.
