GATE 2019 CE (CE1) – Question 55

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

A road has free-flow speed 60 km/h and jam density 120 vehicles/km. With a linear speed–density relationship, find maximum flow (vehicles/h).

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Correct answer: 1800 to 1800

Explanation

For a linear speed–density model, $q=u_fk(1-k/k_j)$. Differentiation gives maximum flow at $k=k_j/2=60$ vehicles/km and speed $u_f/2=30$ km/h. Capacity is **60 × 30 = 1800 vehicles/h**.