Module 2 : Traffic Measurement Procedures
Lecture 07 : Measurement Along a Length of Road
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Numerical Example

A test was conducted to determine the delay in an intersection. Table 1 presents a sample computation on direct observation of vehicle-in-queue counts at the intersection. The traffic signal at the intersection operates with a cycle time of 115 sec. The test was conducted on the 2 lane road over a 15-min period, which is almost thirteen cycles . Count interval was 15-s. The total number of vehicle is 530 and the total number of stopped vehicle is 223. Assume the free flow speed to be 65 km/h and the empirical adjustment factor 0.9
Figure 1: Example of the intersection control delay worksheet
\includegraphics[width = 8cm]{qftable3}

Solution:

  1. Number of lane, N=2
  2. Free-flow Speed, FFS =65 km/h
  3. Survey count interval, Is =15 sec
  4. Total vehicle in queue, $ \Sigma V_{iq}=371$
  5. Total vehicles arriving, $ V_{tot}=530$
  6. Stopped vehicles count, $ V_{stop}=223$
  7. No of Cycle Surveyed, Nc=7.8
  8. Acc./Dec. correction factor, CF=4 (from Table 7.1)
  9. No. Of Vehicles stopped per lane each cycle

    $ V_{stop}{Nc\times N} = \frac{223}{7.8\times 2}=14$

  10. Fraction of vehicles stopping,

    $ FVS=\frac{V_{stop}}{V_{tot}}= \frac{223}{530} = 0.42$

  11. Time-in-queue per vehicle ,

    $ d_{vq} =(Is \times \frac{\Sigma V_{iq}}{V_{tot}})0.9=9.5 sec$

  12. Acc./Dec. correction delay,

    $ dad=FVS \times CF=0.42 \times 4=1.7sec$

  13. Control delay/vehicle,

    $ d=dvq+dad=11.2 sec$