On a circular curve, the rate of superelevation is $e$. While negotiating the curve a vehicle comes to a stop. It is seen that the stopped vehicle does not slide inwards (in the radial direction). The coefficient of side friction is $f$. Which of the following is true:

1. $e \leq f$
2. $f < e < 2f$
3. $e \geq 2f$
4. none of the above