The 'peeing on the front wheel' was never a national law. It was a bylaw adopted by many city councils (including London) allowing Hackney Carriage drivers to pee without leaving their horse and cart where it might get stolen. Given that 'black cabs' operate under 'Hackney Carriage' regulations, then this applies to modern 'black cab' taxi drivers in those areas where it originally applied. There was also, in some cities, an offense of leaving a horse and cart unattended, so the Hackney Carriage driver would be legally obliged to stay with his vehicle. They also had to carry food for the horse (bale of hay = can of petrol) and a way of collecting the waste (bucket & shovel = catalytic converter). I have often wondered, if you are on the motorway and have been caught in traffic jams for a few hours and you absolutely MUST go (to the point of being in pain) and there are no services nearby, what is your legal stance ? I have been told by medical people that not peeing when you REALLY need to can be harmfull.