Using Physics to Beat a Traffic Ticket


Lacking a legal argument to get out of your traffic ticket?  Try physics.  Dmitri Krioukov, a UC San Diego physicist, submitted a four-page physics paper to a city traffic commissioner arguing that three coincidences occurred at the same time, making a nearby police officer believe that he had seen him run a red light, when really he had not.  Krioukov writes in the paper, “We show that if a car stops at a stop sign, an observer, e.g., a police officer, located at a certain distance perpendicular to the car trajectory, must have an illusion that the car does not stop, if the following three conditions are satisfied: (1) the observer measures not the linear but angular speed of the car; (2) the car decelerates and subsequently accelerates relatively fast; and (3) there is a short-time obstruction of the observer’s view of the car by an external object, e.g., another car, at the moment when both cars are near the stop sign.”

You can read the paper Krioukov submitted to the court, “The Proof of Innocence,” here.

In the end Krioukov did get out of his ticket.  However, the San Diego Superior Court commissioner who heard the case, Karen  Riley, states that it was not the physics argument that was persuasive, but the fact that the police officer was not close enough to the intersection to have a good view of the light.

Read more about the case on the San Diego Union-Tribune website.