GATE 2016 CE (CE1) – Question 64

Traffic Engineering and Transportation Planning · Fundamental relationships of traffic flow · 2 marks · Numerical answer

While traveling along and against the traffic stream, a moving observer measured the relative flows as 50 vehicles/hr and 200 vehicles/hr, respectively. The average speeds of the moving observer while traveling along and against the stream are 20 km/hr and 30 km/hr, respectively. The density of the traffic stream (expressed in vehicles/km) is _________

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Correct answer: 2.9 to 3.1

Explanation

For an observer moving with traffic, net count satisfies q−20k=50. Against traffic, the count is q+30k=200. Subtracting eliminates q:50k=150, so **k=3vehicles/km**. Substitution gives q=110vehicles/hour, checking both observations.