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Speed zoning studies are conducted to evaluate safety issues and identify appropriate speed limits for specific roadway segments. In addition to actual travel speeds, there are several other types of information that may be appropriate input to the process of setting speed limits.
Spot speeds are useful to study paints of congestion, for locating traffic signals, or for enforcing speed limits. Running speeds are useful to assess the traffic capacity of highways.
Assessing roadway safety questions. Evaluating and verifying speeding problems. Assessing speed as a contributor to vehicle crashes. Investigating input from the public or other officials.
Methods in conducting Spot Speed Study. Manual methods: To observe the time required by a vehicle to cover a short distance. Two reference points are located at a roadway at a fixed distance apart.
Speed data is needed for a variety of traffic analyses. Spot speed data refers to measurement of individual speeds of vehicles passing a point on a roadway. Care must be taken to conduct the study appropriately so that the sample data will adequately reflect speed characteristics of the population.
These are compared from point to point along the route, and the difference in time values, through use of synchronized watches, is computed. This method requires careful and time-consuming office work and does not show locations, causes, frequency, or duration of delay. Four basic methods are:
Running Speed (RS). The test vehicle’s average speed (in miles per hour) while the vehicle is in motion (does not include delay time) it can be calculated by the formula: RS = Distance TT - D Running Time (RT). The elapsed time (in seconds) excluding delay spent driving a distance. Special Control Points (SCP).
