The problem is that whilst \s* is greedy, it will also match zero spaces, which means that '1/2' followed by zero spaces is not followed by 'MILE', because it is followed by ' MILE' which satisfies the condition, so the expression is true.
The only thing that overrides a regexes natural greediness is it's desire to achieve a match. If it can, it will, and it can, so it does:)
Examine what is said, not who speaks.
"Efficiency is intelligent laziness." -David Dunham
"When I'm working on a problem, I never think about beauty. I think only how to solve the problem. But when I have finished, if the solution is not beautiful, I know it is wrong." -Richard Buckminster Fuller