Hello

The maximum achievable speed is the minimum value of the maximum speeds of the various objects involved. You must therefore take the minimum value of the speeds of: tracks, locomotives, carriages. To be clear, a very fast locomotive with slow carriages or old tracks will never go at its maximum speed.

Another factor to consider, the weight of the train. If you add too many carriages it will not be able to go at maximum speed, in extended to each added carriage you will be shown the maximum speed that can be reached by the train.

Giuseppe