Continuity mistake: In War Dance (4-2) the verger Mr. Yateman's wife's Christian name is Anthea. In Everybody's Trucking (8-1) it is Beryl, and in Knights of Madness (10-3) she is called Tracy.
Continuity mistake: (Colour episodes only) In the section of the closing credits that features the main cast members marching, the sky colour and positions of the shadows on the ground change depending on the actor being featured at the time (the sky is blue when Arthur Lowe, John Laurie and Ian Lavender are seen, but it is grey when John Le Mesurier, Clive Dunn, James Beck and Arnold Ridley feature). This is more obvious on episodes that have had colour restoration undertaken.
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.