The cost of transmission development, especially for automatic transmissions, requires special methods for evaluating both power transfer and fuel consumption. Previous methods have deviated substantially from actually driving conditions; consequently, data for this investigation was based on driving cycles consisting of:1) acceleration at full engine loading2) driving at constant speeds ranging from 35 to 60 km/h3) braking at 1 m/s2 decelerationTest results on a Diesel-equipped, city bus indicated:1. Automatic transmissions are advantageous and economical, especially at high speeds.2. Manual shifts can be improved through shorter gear-shifting times.3. Potential use of unstepped transmissions are promising if optimal means of control are incorporated.4. Theoretically, energy storage can provide significant savings, but the complexity of its practical application makes its implementation unlikely.Although the tests were run on a city bus, the analytical approach can be applied to more complicated driving patterns of other heavy vehicles.