21. Name three methods or devices that are used to collect traffic data. 22.Usin

Question

21. Name three methods or devices that are used to collect traffic data. 22.Using Greenshield's model, what is the speed of traffic if the free-flow speed is 55 mph, the jam density is 80 veh/mi, and the current density is 50 veh/mi? 23. Using Greenberg's model, what is the speed of traffic if the free-flow speed is 55 mph, the jam density is 80 veh/mi, and the current density is 50 veh/mi? 24. Using Underwood's model, what is the speed of traffic if the free-flow speed is 55 mph, the jam density is 80 veh/mi, and the current density is 50 veh/mi? 25.Where are car-following models mainly used?

Explanation / Answer

(1) Answer:- Three instrument used for traffic data control:-

(i) Pneumatic tubes

(ii) Inductive loops

(iii) Weigh in motion sensor types.

(2) Solution:-

Greenfield Model:-

V = Vf - (Vf/Kj )*K

    = 55 – (55/80) * 50

V = 20.62 mph    Answer

(3) Solution:-

Greenberg model

V = V0*ln(Kj/K)

V = 55 * ln( 80/50)

V = 25.85 mph Answer

(4) Solution:-

Underwoods model

V = Vf * e(-K/K0)

V = 55* e(-50/80)

V = 29.439   Answer

(5) Answer:-

Car following models:- One aspect of interest in car following is the average spacing S , that one vehicle would follow another at a given speed V

C = 1000 * (V/S)

C = capacity of single lane

V = speed (km/hour)

S = average spacing rear bumper to rear bumper in meter

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