Question

A 5° curve (measured at the centerline of the inside lane) is being designed for a highway with a design speed of 100 km/h. The curve is on a 2% upgrade, and driver reaction time may be taken as 2.5 seconds. What is the closest any roadside object may be placed to the centerline of the inside lane of the roadway while maintaining adequate stopping sight distance?

Answer 1

SSD = 0.278vt + v² /254( + x/100)

= 0.278 x 100x2.5 + 100² /254(0.29 + 2/100) for 100 km/hr, f =0.29

= 196.50 m

Closest any roadside object may be placed to the centerline of the inside lane of the roadway while maintaining adequate stopping sight distance

Mid ordinate

M = R - R cos /2

/2 = (SSD /2R) x 180/π

R = 5730/D = 5730/5

R = 1146

/2 = (196.50 /2x1146) x 180/π

= 4.912

M = R - R cos /2

= 1146 - 1146 cos4.912

= 4.209 m