When a motorcyclist taps his helmet, it is usually a warning message to other riders that members of law enforcement are nearby and are monitoring traffic. This is a signal to slow down and adopt a well-behaved riding attitude to avoid getting a ticket. In most of the U.S., this is a warning that the police are nearby, which could be any number of scenarios where the police would typically be present, such as an accident, a road closure, an officer waiting to catch speeding motorists, or an officer who’s already pulled over a speeding motorist. It is important to slow down and be cautious when you see this warning from other riders.