A vehicle is moving on a two-lane highway with design speed of 65 kmph on a horizontal curve of radius 300 m. What is the required length of transition curve based on rate of introduction of super elevation? Consider width of pavement = 7.5 m, rate of super elevation, e = 0.06, rate of introduction of super elevation, N = 1 in 150 and outer edge of the pavement is rotated with respect to centre line.

A vehicle is moving on a two-lane highway with design speed of 65 kmph on a horizontal curve of radius 300 m. What is the required length of transition curve based on rate of introduction of super elevation? Consider width of pavement = 7.5 m, rate of super elevation, e = 0.06, rate of introduction of super elevation, N = 1 in 150 and outer edge of the pavement is rotated with respect to centre line. Correct Answer 33.75 m

Concept:

The length of the transition curve should be determined as the maximum of the following three criteria: rate of change of centrifugal acceleration, rate of change of super-elevation, and an empirical formula given by IRC.

BASED ON RATE OF CHANGE OF SUPERELEVATION AND EXTRA WIDENING:

Let 1 in N is the allowable rate of introduction of superelevation and E is the raise of the outer edge with respect to the inner edge. W is the normal width of pavement in meters. W_e is the extra width of pavement in meters and e is the rate of super-elevation.

If the pavement outer edge is raised and the inner edge is depressed with respect to the center of the pavement then,

L_s = / 2

For simplicity we can ignore value of extra widening for objective type of question.

So, L_s = eNW/2

Calculation:

Given,

e = 0.06, N = 150, W = 7.5 m
∴ L_s = eNW/2

L_s = (0.06 × 150 × 7.5)/2 = 33.75 m