[BUG]: Choose signal fails to find alternative route

[freddyhayward]

I'm unsure what's causing this. In my testing, choose signals can find routes around obstructions heading east and south, but fail heading west and north, causing vehicles to wait for clearance forever.

[jamespetts]

Thank you for the report: I believe that I have now managed to fix this. I should be grateful if you could re-test with the next nightly build.