you CAN use your horn, to let other drivers know of your presence, and by doing so stops an accident happening. you cannot sound your horn while stationary between the hours of 2300 to ( i think ) 0700 hours in built up areas, so those taxi drivers that do are breaking the law, and quite honestly if thats the attitude of the police i am surprised that there has been as few accidents with pedestrians due to their careless driving, this unelected goverment must train them better before plod kills another innocent.