Module 2 : Traffic Measurement Procedures
Lecture 08 : Automated Traffic Measurement
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Numerical Example

  1. If the vehicle 10% time occupied by loop M and 32% time occupied by loop N, the distance between two loops are 4.22 m find the spot speed of the vehicle. Also find the length of the vehicle if time occupancy for M - loop is 0.26sec and 0.32 for N-loop?

    Solution: Length is 4.22 m and occupancy times are 0.32 and 0.1.Therefore,the spot speed(v)is given by:
    $\displaystyle v$ $\displaystyle =$ $\displaystyle \frac{l_{dist}}{t_2 - t_1},$  
      $\displaystyle =$ $\displaystyle (4.22)/(0.32 - 0.1) = 19.18~\mathrm{m/sec}.$  

    For length calculation, the speed is 19.18 m/sec and occupancy times are 0.26 and 0.32.
    $\displaystyle L_{vehicle}$ $\displaystyle =$ $\displaystyle \frac{Speed(ot_2 + ot_1)}{2},$  
      $\displaystyle =$ $\displaystyle \frac{19.18(0.26 +0.32)}{2} = 5.56~\mathrm{m}.$  

  2. The average length of vehicle is 4.25 m and the length of loop detector zone is 1.85 m. The time occupancy in the loop is 32 percentages, find the spot speed of the vehicle?

    Solution: The average vehicle length is 4.25 and detector zone length is 1.85 m and t0 is 0.32.The spot speed(s)is given by:
    $\displaystyle s$ $\displaystyle =$ $\displaystyle \frac{EVL}{t_o},$  
      $\displaystyle =$ $\displaystyle \frac{4.25 + 1.85}{0.32} = 19.06~\mathrm{m/sec}.$  

  3. In freeway 1500 vehicles are observed during 120 sec interval. The lane occupancy is 65 percentage and the average length of vehicle observed as 6.55 m. Find the space mean speed on the freeway section?

    Solution: The number of vehicle N is 1500 vehicles; observation period is T= 120 sec.
    The lane occupancy O is 0.65 and average length is 6.55, so g is (40.9/6.55).The space mean speed(s) is given by:
    $\displaystyle s$ $\displaystyle =$ $\displaystyle \frac{N}{T \times O \times g},$  
      $\displaystyle =$ $\displaystyle \frac{1500 \times 6.55}{120 \times 0.65 \times (40.9)}$  
      $\displaystyle =$ $\displaystyle 3.08~\mathrm{m/sec}.$