Question

A transportation engineer uses the formula, R = (1600)/(15+127e), to determine the minimum radius of curvature (R) in meters, for a roadway with a 40 km/hr design speed and a maximum superelevation rate (e). What is the maximum superelevation rate recommended if the radius of curvature is 400 meters? Answer as a decimal, rounded to two decimal places.

Answer 1

From the problem, we have the formula for the radius of curvature :

`R=(1600)/(15+127e)`

If the radius of curvature is 400 meters, the super elevation rate (e) is :

`\begin{gathered} 400=(1600)/(15+127e) \\ \text{Cross multiplication :} \\ 400(15+127e)=1600 \\ 6000+50800e=1600 \\ 50800e=1600-6000 \\ 50800e=-4400 \\ e=(-4400)/(50800) \\ e=-0.09 \end{gathered}`

ANSWER :

e = -0.09