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•Determine following characteristics of spot speed – mean, median, mode, pace, 85th percentile, sd •Fit a speed distribution •Check for normality •Comparison of assumed versus observed distribution
Spot speed studies are used to determine the speed distribution of a traffic stream at a specific location. The data gathered in spot speed studies are used to determine vehicle speed percentiles, which are useful in making many speed-related decisions.
Spot speed studies are conducted to estimate the distribution of speeds of vehicles in a stream of traffic at a particular location on a highway. The speed of a vehicle is defined as the rate of movement of the vehicle; it is usually expressed in miles per hour (mi/h) or kilometers per hour (km/h).
A stopwatch spot speed study includes five key steps: 1. Obtain appropriate study length. 2. Select proper location and layout. 3. Record observations on stopwatch spot speed study data form. 4. Calculate vehicle speeds. 5. Generate frequency distribution table and determine speed percentiles.
At this stage of the analysis, it is already possible to calculate the mean speed, mode, and pace as demonstrated below. • • The mode is 29 mph as it is the observed speed that was most frequently observed, as it was observed for 26 vehicles.
Spot speed studies are conducted to estimate the distribution of speeds of vehicles in a stream of traffic at a particular location on a highway. Speed: the rate of movement of a vehicle (mi/h) or (km/h). Carried out by recording the speeds of samples of vehicles at specified location.
1. Calculate the 95th, 85th, and 15th percentile speeds and the 10 miles per hour pace speed range. Equipment – Radar Unit, Laser Unit or Stop watch. Locations – where drivers can obtain uninterrupted free flow speed. (i.e. tangent sections, outside of braking area for intersection)
