Question 1043507
Center of the rode is like the origin on a cartesian coordinate plane.
{{{x^2/18^2+y^2/15^2=1}}}
Solve for y and use the upper branch.


Decide how you want the truck to be positioned; middle over the center line of the rode, or none of the truck crossing the center line.  How tall is the truck?  Width is only part of the problem to solve.  


Imagine the truck will drive in the middle of the rode to try to pass under the tunnel.  This leaves 6 feet on either side of the center of the rode.  Now, what must y be?  Is the truck too tall for this?