All motorists must honk before passing another car, bicyclist, skater, and even a skateboarder.

Lipka, Mitch. Honk Before Passing? Few Do. The Philadelphia Inquirer. 13 Mar. 2003.

One must make a loud noise before passing a car on the left.

While passing another vehicle, you must honk your horn.

Citizens must honk their horn while passing other cars.

Drivers must warn those who they pass on highways before they do so.

Traffic police must report all bribes that they receive from motorists.