Speed Zone Survey

Speed Zone Survey Equipment - Proper equipment is essential for an accurate speed zone survey measurement of the uninterrupted free flow of traffic, including:

An unmarked (no police markings), plain colored vehicle.  If the vehicle is equipped with flashing lights, the lights must be taken off the vehicle and placed inside the vehicle to not affect the drivers’ speed of traffic.  The vehicle must be of a kind not to attract attention or cause drivers to slow down.  Marked police vehicles cannot be used.

Portable Radar or Lidar should be used to conduct the spot speed zone survey speed measurements. The accuracy of the radar or the lidar should be verified to assure the reviewing engineer the subject study vehicle speeds were accurately measured to within 3 mph.

Prior to use of the speed detection Radar or Lidar equipment for the speed zone study all such equipment must be calibrated the same way as radar or lidar is calibrated and used by law enforcement.

All automated data gathering equipment such as pneumatic hoses should only be used to assist personnel that have proper training.  Automated equipment cannot determine the vehicle’s state of free flow, therefore trained personnel must use their training to eliminate the non-free flow vehicles from the data table for speed zone study.

The personnel must be trained and understand the principals and impact of the cosine effect to avoid recording data for vehicles that are impacted and ignore such data in the speed zone survey.

The cosine effect shows that the speed measured by the radar (or other device), Vm, can be an inaccurate measurement of the vehicle’s actual speed, Vo depending on angle, a, between the radar’s line of sight (LOS) and the vehicle’s direction of travel.  One can minimize the difference between Vm and Vo by minimizing the perpendicular distance, d, between the radar and the vehicle’s direction of travel.

Location of Speed Measurements for speed zone survey

Locations to take the spot speed measurements should be carefully selected to provide true free flow speeds. All uncharacteristic locations should be avoided.  Speed Zone Surveys must not be conducted at:

• Intersections with traffic signals or stop signs
• Roadway narrowing for a short period
• Unsignalized intersections or driveways with high turning movements
• Any location affected by emergency personnel
• Roadwork or law enforcement presence

In California to use electronic speed detection devices such as radar or lidar for speed enforcement, a valid speed zone survey is required. In most cases the violation code 22350 vc is used for roadways where the speed limit has been reduced below the maximum speed limit based on the 85th percentile speed. If the speed zone survey is not valid or it does not follow the requirements of the California Vehicle Code then a speeding ticket for 22350 vc can be contested. If you have a speeding ticket and if you would like to fight your speeding ticket without going to court using a trial by written declaration, we can help. Signup for our service and take advantage of our 100% money back guarantee. We provide trial by written declaration samples and examples to fight speeding tickets.