How long should a station platform be?

The platform will need to be as long as the longest rake of coaches you are running plus the length of the engine.

Many people fall foul of not allowing for the length of the engine but you need to remember the driver needs to get out as well! Obviously this mistake makes the platform too short.

If you look at any photograph of a railway station you will see that the platforms are extremely long to accommodate the longest of trains.

As an example, a steam train like a Flying Scotsman or Mallard with only 3 coaches behind (so quite a small train) will require a platform about 90cm long (that is 3 feet) in OO gauge.