Numeric

3 link coupling
See Couplings

4 foot
A commonly used term for `between the rails' (UK standard gauge being 4 foot 8½ inches).

6 foot
Commonly used term for the space between two adjacent tracks.

7 year overhaul
Steam locomotives working on the National Network are required to undergo thorough boiler examinations every 7 years.

10 year overhaul
Steam locomotives working on independant railways are usually required to undergo thorough boiler examinations every 10 years, although this may sometimes be extended.