A vehicle is moving with uniform speed along 3 different shaped roads as horizontal, concave and convex. The surface of road on which, the normal reaction on vehicle is maximum is

The normal reaction on the vehicle is determined by analyzing the forces when moving at uniform speed v on different surfaces.

On a horizontal road, the gravitational force mg is balanced by the normal reaction N_H, giving N_H = mg.

At the lowest point on a concave road, the centripetal force mv²/r is provided by the normal reaction exceeding gravity: N_C − mg = mv²/r, leading to N_C = mg + mv²/r.

At the highest point on a convex road, gravity exceeds the normal reaction to provide the centripetal force: mg − N_X = mv²/r, so N_X = mg − mv²/r.

Comparing the expressions shows N_C > N_H > N_X, indicating the maximum normal reaction occurs on the concave road.

The answer is $\boxed{B}$.