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SPOT SPEED STUDY
Transcript of SPOT SPEED STUDY
performed by measuring a series of individual speeds of the vehicles passing a given point (spot) on a street or highway.
used to estimate the speed distribution of the entire traffic stream at that location under the conditions prevailing at the time of the study.
Spot speed studies are undertaken for relatively short time periods.
Method of Conducting Spot Speed study
(1) stopwatch method,
(2) radar meter method, or
(3) pneumatic road tube method
Application of spot speed data
For speeds at the problem locations, to determine whether speeds are too high and if complaints received are justified
For traffic operation:
- To establish speed limits
- To determine safe speeds at curves
For geometric design features
Driver - distance of his trip, the no. of passengers, age residence;
Vehicle - including type, age, weight, manufacturer and horse power;
Roadways & Environment- including the graphic locations, type, grade, sight distance, no. of lanes frequency and spacing of intersections, including volume, density, passing, passing movements, speed regulations, including time of day and weather
Factors effect spot speed studies:
ROADWAY & ENVIRONMENTS
Where to make spot speed studies?
Straight, level, open sections of rural
Midblocks locations on urban streets
High accident frequency purposes
At points where the installation of traffic signals and traffic signs is contemplated
- To observe the time required by a vehicle to cover a short distance.
- With the direct timing procedure
- Two reference points are located at a roadway at a fixed distance apart.
- Observer starts and stops a stopwatch as a vehicle enters and leaves the test section.
- It is most uncomplicated way.
- Disadvantage because of parallax effect
Pneumatic road tube method
Radar Meter method
Using reflected waves (radar meter detector).
Very high frequency is directed from the radar speed meter to the moving vehicle.
The waves which is directly measurable is proportional to the speed at which the vehicle is moving.
Should be within a cone of 20 of the line of the vehicle movement.
Following actions might be considered after determining the spot speed analysis:
adjust the posted speed limit
increase speeding enforcement
propose traffic calming measures
increase public awareness efforts
To observed the pattern of speed trend
To perform simple statistical analysis on speed samples collected and interpret the result obtained
- Identify the spot at which the data will be located
- Use the radar gun to measure the speed of vehicles according to their respective class
- Record the speed measurements for at least 150 vehicles in form SS1
- Based on the data, determine the mean, median, modal speed and standard deviation
- Plot the Frequency Histogram and Cumulative frequency curve to get the 85th percentile speed (Speed Limit)
- Comments on your findings