The most widespread grade-separated road junction — cloverleaf interchange — is a complex engineering structure, in which all the parameters and limitations of the plan and longitudinal profile must be coordinated with each other. The goals of the analysis: traffic safety, technical and economic indicators of the movement of transport units, the compactness of left-turn and right-turn exits and, as an additional, but extremely important aspect, the minimization of the area occupied by the entire transport structure, which is very important in tight urban conditions. 
 First, let's emphasize that the trajectories of cars at the intersection must correspond to their real variable speeds on left-turn exits, since this is traffic on curves of small radii. In our previous studies, it has been experimentally proven that cars entering a left-turning exit reduce their speed, and conversely, when leaving the exit, their speed increases. Therefore, it is necessary to use braking curves as transition curves of left-turn exits, and not clothoid curves, which are often used, and which are designed for constant speed of movement.
 Some braking transition curves designed for variable speed are also used in traffic junctions [4]. But, analyzing these curves, we came to the conclusion that they do not meet the classical purpose of the transition curve, namely, they do not provide the necessary radius at the end of the curve, which is equal to the radius of the circular insert for a smooth transition from a transition curve to a circular curve. This leads to dangerous moments of the car's movement at the junction of the transition and circular curves.
 Therefore, we previously derived the formulas of refined braking transition curves that meet the requirements of the radii of classical transition curves [1, 2]. In addition, it later turned out that these refined transition curves have, as an additional effect, the property of reducing the area occupied by the left-turn exit, as shown in Fig. 1.
 We offer a method for optimizing the spatial parameters of cloverleaf interchanges with refined braking transition curves.