Trivia: The only member of the cast to have actually served in the Home Guard was John Laurie. Arthur Lowe, John Le Mesurier, Clive Dunn and Arnold Ridley were in the regular army.
Trivia: Hodge's BSA motorbike, reg. no. JVB54, used in Dad's Army is the same one used in the TV series on the buses as Arthur's motorbike.
Trivia: Clive Dunn was a prisoner of war during World War 2.
Trivia: Godfrey's middle initial is 'P'. This is probably a reference to his character's trait of constantly getting 'caught short' (needing to go to the bathroom).
Trivia: Jon Pertwee was the producers' first choice for the role of Captain Mainwaring.
Answer: The show is a comedy, this was played for comedic effect and to show that in times of extreme fear, in this case about to be crushed by a steam train, the men had an adrenaline surge strong enough to pedal fast enough.