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Although the problem/the post is written in good English, it does not make sense.
Two evident solutions come to the mind first.
a) Hypotenuse.
But how do you know that there is straight way/street/highway available along the hypotenuse ??
What if there is a huge lake between the starting and ending points ??
b) Returning back by the same way as the driver got the final point . . .
But how do you know that the way back is two-side street . . . ?
Therefore I say that the problem formulation presented makes no sense.