The infraction or offense of speeding is committed when the driver of a motor vehicle exceeds the posted speed limit or exceeds the speed limit that is reasonable and prudent under the circumstances or conditions—such as the road (straight, curved, wet, dry, icy, flat, hilly); the weather (clear, foggy, raining, snowing); and the visibility (smoke from a grass fire or a tractor trailer obstructing the view).

Speeding laws (and enforcement) vary from state to state and among cities and towns (local ordinances) and are usually located in a state’s statutes. The penalty for speeding is usually a fine and demerit points added to the driver’s license or driving record.

To measure the speed of a moving vehicle and issue speeding tickets, police officers generally use radar guns that rely on radio signals and the Doppler Effect, or Light Detection and Ranging (LIDAR) technology that relies on lasers rather than radio waves. These devices require training on their proper use and regular calibration to be accurate.

In Washington State (WA), the offense of speeding occurs when a driver operates a vehicle at a speed exceeding the posted limit or drives too fast for the current conditions, considering factors such as road characteristics, weather, and visibility. Washington's speeding laws are codified in the Revised Code of Washington (RCW), particularly in Title 46, which pertains to motor vehicles. Penalties for speeding typically include fines and the accumulation of demerit points on the driver's record, which can lead to increased insurance rates and, with enough points, license suspension. Law enforcement officers in Washington use radar and LIDAR technology to measure vehicle speeds. These devices must be properly calibrated and operated by trained officers to ensure accurate readings. If a driver believes a speed measuring device was inaccurate or improperly used, they may challenge the speeding ticket in court with the assistance of an attorney.