Perhaps I am misunderstanding the question…
However, this seems far more elegant
Design/draw a road network with two points a and b such that the fastest route between a and b is not the shortest route.
error in solution?
I may be wrong but I think there is a typo in the proposed solution.
So the distance from a to b through d is 10 miles. Assuming you drive 30 miles per hour, the time to travel this would be 20 minutes, but due to the busy intersection at d, you are delayed 15 minutes, the total time would be 35 minutes.
Shouldn't it be:
d instead of c right?