This problem stems from この先 being able to mean “ahead from here in space”, or in time which (mis)translated to “the future”. Without proper context (that it is a sign on a road) the translation software had to make a guess, and it guessed wrong.

It may be possible to infer from 前へ行く in the second sentence that it is more likely referring to space than time, but I still think it is possible to construct some similar sentences which even humans might misunderstand.