Traffic Infraction Information

A traffic infraction is NOT a criminal offense. A traffic infraction is a violation of the rules of the road set forth in RCW Chapter 46.61 and related sections. The most common traffic violation is "speeding." If you get a speeding ticket, you might consider the deferral process. This process is explained at

Speed traps, RCW 46.61.470.

No evidence obtained in a speed trap is admissible as evidence unless the state can show compliance with RCW 46.61.470 (2) which reads:

  • Evidence shall be admissible against any person arrested or issued a notice of a traffic infraction for violation of any of the laws of this state or of any orders, rules, or regulations of any city or town or other political subdivision regarding speed if the same is determined by a particular section of or distance on a public highway, the length of which has been accurately measured off or otherwise designated or determined and either: (a) The limits of which are controlled by a mechanical, electrical, or other device capable of measuring or recording the speed of a vehicle passing within such limits; or (b) a timing device is operated from an aircraft, which timing device when used to measure the elapsed time of a vehicle passing over such a particular section of or distance upon a public highway indicates the speed of a vehicle.
  • The exceptions of subsection (2) of this section are limited to devices or observations with a maximum error of not to exceed five percent using the lapsed time during which such vehicle travels between such limits, and such limits shall not be closer than one-fourth mile."

A speed trap is defined as:

"...A "speed trap," within the meaning of this section, is a particular section of or distance on any public highway, the length of which has been or is measured off or otherwise designated or determined, and the limits of which are within the vision of any officer or officers who calculate the speed of a vehicle passing through such speed trap by using the lapsed time during which such vehicle travels between the entrance and exit of such speed trap...."

Radar (Doppler)

Police traffic radar results are admissible in a criminal prosecution if the particular radar device used is shown to be reliable. The reliability of a radar device requires: (1) testimony of the police officer who used the device to measure the speed of the defendant's vehicle that the device was functioning properly when so used and (2) testimony from a qualified expert that the device passed the requisite tests and checks to ensure its operational accuracy.

You have the right to require expert testimony concerning the operational accuracy of the device. See IRLJ 6.6; Seattle v. Petersen, 34 Wn. App. 524 (1985), Bellevue v. Lightfoot, 75 Wn. App 214, 877 P.2d 247 (1994). See also RCW 46.61.470.

Radar (Laser)

The laser gun, unlike Doppler Radar, uses invisible light pulses to record the speed of a moving vehicle. All laser devices emit a very narrow, intense beam of light. With laser speed guns, the light is just outside the visible spectrum in the 701 to 10,000 nanometer range. The laser speed gun calculates the distance by measuring the legth of time it takes for the beam to reflect back from a target. The LTI 20-20 is the most common device and was first produced in 1986.

Note: Refraction errors can produce incorrect speed readings. Because the light is refracted differently by hot air than cooler air, a spot of air rising from the roadway can confuse the laser. When the laser beam bounces off more than one solid object, refraction errors also occur, producing an incorrect speed reading. The laser is also affected by dust, water vapor and exhaust fumes in the air.