Multiple choice

A roundabout is provided with an average entry width of 8.4 m, width of weaving section as 14 m, and length of the weaving section between channelising islands as 35 m. the crossing traffic and total traffic on the weaving section are 1000 and 2000 PCU per hour respectively. The nearest rounded capacity of the roundabout (in PCU per hour) is

  1. 3300

  2. 3700

  3. 4500

  4. 5200
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B Correct answer
Explanation

Wardrop's formula for roundabout capacity: C = (284 * w * (1 + e/w) * (1 - p/3)) / (1 + w/l). Given w=14, e=8.4, l=35, p = 1000/2000 = 0.5. C = (284 * 14 * (1 + 8.4/14) * (1 - 0.5/3)) / (1 + 14/35) = (3976 * 1.6 * 0.833) / 1.4 = 5298 / 1.4 = 3784. The closest value is 3700.

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