The paper describes a programme which has been prepared for a high-speed digital computer for calculating speed/time curves, energy consumption and motor heating for a train with given characteristics travelling on a given route. The analysis prior to the preparation of the programme is given in some detail to illustrate the preliminary work necessary before a problem can be solved on one of these machines. The results of a sample calculation of the performance of d.c. 4-motor-coach trains on the Liverpool Street-Shenfield line of the Eastern Region of British Railways are given and compared with actual performance.The possibility of using digital machines in connection with a number of other traction problems is also discussed. These problems are fuel-economy studies, the design of overhead structures, weight-transference calculations, the spacing and loading of substations, the study of rectifier harmonics, the compilation of timetables and traffic cost studies.