There is a special font they use - very like helvetica but with a couple of tweaks.Off the top of my head I think you can download it from Dept of Transport's website somewhere.
what does google have to say on the matter?
(what does google have to say on the matter?
barryheadwound Mul-ti-pass? Multipass!,
Thu 4 Dec 2008, 16:03,
archived)