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Traffic engineering miscellaneous

Traffic Engineering

  1. On an urban road, the free mean speed was measured as 70 kmph and the average spacing between the vehicles under jam condition as 7.0 m. The speed-flow-density equation is given by
    U = Usf1 -
    k
    and q = UK
    k1

    where, U → space-mean speed (kmph); Usf → free mean speed (kmph); k → density (veh/km); kj → jam density (veh/ km); q → flow (veh/hr). The maximum flow (veh/hr) per lane for this condition is equal to
    1. 2000
    2. 2500
    3. 3000
    4. None of these
Correct Option: B

u = usf1 -
k
kj

q = uk
q
= usf1 -
k
kkj

⇒ q = usf1 -
k
k
kj

Diff. w.r.t.k,
dq
= 0 ⇒ usf1 -
2k
= 0
dkkj

⇒ k =
kj
2

∴ qmax = usf = 1 -
1
×
kj
= usf ×
kj
224

= 70 ×
1000
= 2500
7 × 4



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