On my last trip to London, I spent a lot of time on the number 23 from Westbourne Park to Liverpool Street (and Liverpool Street to Westbourne Park), getting down and climbing back on whimsically. Armed with my camera phone and the will to stand next to the information display rather than sit comfortably, I clicked a lot of photographs of the LED letters.
The lowercase letters are five units high. The ascenders and capitals extend two units upwards, and the descenders are two units deep. Every letter space comprises a single unit and word space three units. Here is a selection of images—