The following table presents occupancy output from two 6-ft in-pavement loop det

Question

The following table presents occupancy output from two 6-ft in-pavement loop detectors during a 30-second observation period. The output indicates the times at which each detector had a vehicle enter and exit the detection zones (starting from an arbitrary time zero). The detectors are spaced such that the front edge of the second detector is 16 ft downstream from the front edge of the first detector. Based upon these data, you are asked to estimate the following: Speed of each vehicle Length of each vehicle Mean speed for all vehicles Flow rate Density This dual detector setup has been shown to outperform single loop detectors. Provide an explanation for why this would be the case. Provide appropriate references if necessary.

Explanation / Answer

the distance bettween two starting points is 16 feet = 4.8768 meters

So speed of each vehicle can be calculated by speed =Distance/time formula as

speed = 4.8768/(tsu - tsd) (1)

where tsu = time start at up stream and tsd = time start at down stream

for the length of each vehicle we get the speed of each vehicle from (1) using again the speed-time formula

we have leangth of vehicle = speed * (tsu - teu)

where teu = time end at up stream

- Mean speed ofall vehicles can be calculated by = (sum of speeds of all vehicles)/(total no of vehicles = 8)

- Flow rate = no of vehicles that pass in span of 30 sec = 8/30 = 0.27 vehicles per second

-

tsu teu tsd ted (tsu - tsd) (tsu - teu) speed length 2.00 2.23 2.15 2.38 0.15 0.23 5.00 5.21 5.13 5.35

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