Train drivers from rail union ASLEF on strike at Derby railway station over planned changes by East Midlands Trains to their pensions.
Members of the drivers' union Aslef plan further stoppages on Thursday and on May 8, 10, 15 and 17.
A reduced service will be in place today, and again on Thursday, with a replacement bus services in operation on many routes.
East Midlands Trains says it will aim to provide as many seats as possible for people travelling to the Olympic Games.
Communications have broken down between East Midlands Trains and ASLEF, as the union confirms train-drivers will strike during the Olympics
Train drivers are staging three days of strikes during the Olympics in a row over pensions.