Speed Zone Study

Speed Zone Study under free flow conditions- The intent of the speed zone study is to determine the actual speed of unimpeded traffic in free flow condition. A free flow condition exists where a vehicle’s speed is not influenced by anything other than the roadway geometry.  The conditions that are present in a free flow traffic are:

• There must be at least 5 second gap between vehicles
• There must be enough distance to reach a steady speed that is not influenced by acceleration or deceleration speeds due to traffic signals, stop signs, or other traffic control devices
• There must not be slow moving vehicles such as; trucks or buses
• There must not be speed enforcement or the perception of speed enforcement, police activity, construction or lane closures, inclement weather (rain, fog, snow) or special event traffic
• Measuring Vehicle Speeds for Speed Zone Study
• The speed data collected during the spot speed survey are used to determine the 85th percentile speed or the critical speed. Therefore, extra care must be taken to obtain an accurate measurement of free flow traffic speed. The guidelines for conducting a spot speed survey include:
• The spot speed survey locations must be selected that are representative of the roadside development, pedestrian and bicycle traffic, and other physical conditions for the entire posted speed limit area
• In urban areas, the speed zone study locations should be at 0.25-mile apart to ensure representation of the unimpeded speeds midway between traffic signals or 0.2 miles away from signals, whichever is less
• In rural areas, speed zone study locations may be more than 0.25 miles, provided the roadside development, pedestrian and bicycle traffic, and other physical conditions remain consistent
• Collect speed data for speeds that are representative of the entire speed zone section
• The data sample size must be at least 100 vehicles in each location for the speed zone study
• All speed data must be recorded directly from the speed detection radar device or other electronic speed measuring devices
• Collect speed data on speeds in both directions for all types of roadways, during any daytime period with free-flowing traffic and under dry conditions and clear visibility
• The data collection equipment should not be in a location that will affect the traffic speeds before the speed is measured
• Vehicles with more than two axles or towing a trailer should be ignored for speed data
• Speed data collection must be avoided in the roadway horizontal or vertical alignments (i.e., curves or steep grades)

In California the use of radar or lidar for speed enforcement requires a valid speed zone survey. In most cases, the violation code 22350 vc is used for roadways where the speed limit was reduced below the maximum speed limit law. 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.