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 :

$R=\frac{1600}{15+127e}$

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

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

ANSWER :

e = -0.09