The article is aimed to determination of necessary condition of wheel rolling onto the rail head for heterogeneous train made up of empty and loaded cars using a simplified algorithm for computing the longitudinal compressive forces. It was investigated the distribution of the maximal compressive forces in the train sections during emergency and service braking. To determine the dynamic longitudinal compressive force the differential equations of the mass center movement of the fore and tail parts of the train are formulated. The cross section is set in which it is necessary to determine the longitudinal force, the time of passage of the braking wave along the train and the time of the passage of braking wave to the defined cross-section, the difference of mass centers velocities of the fore and tail train parts. Based on the results the maximum value of the dynamic longitudinal compressive force acting on a particular car is calculated. In calculating the radius of the curve elevation and train speed are taken as the constant values. Object of research is a freight train formed of thirty empty and thirty loaded cars moving in the curved track section. The article studies the dynamic values of longitudinal compressive forces that occur in a particular section of the train during service and emergency braking. It was studied the distribution of maximum compressive forces in the cross sections of the train during service and emergency braking. The check of execution of necessary condition of wheel rolling onto the rail head for thirtieth empty car during service and emergency braking was completed. The algorithm of simplified calculation of the maximal longitudinal forces in heterogeneous cross sections of the train when braking was improved. There were determined compressive forces in the train and checked the conditions of wheel rolling onto the rail when moving in a curved track section. It was shown that the irrational train forming can result in efforts, which can cause cars derailment. The obtained results can be used to establish the causes of rolling stock derailment during the railway-transport expertises, as well as to conduct estimating calculations when forming the trains.