This job was too much fun to not do it...
The customer turned up with a board that looked like this:
It had been running for about 16 years, but was undocumented and unreliable. I persuaded them to go for the nuclear option, and designed this:
The processor is a P18, with plenty of I/O
It is fitted inside this:
Fun bits included radio calling from each bank, 60GHz radar to detect the bank and anything in the direction of travel, speed control, interlocks with gates and other bits of user interface...
It runs across the Thames, about 50 miles west of London.