Understanding the “Makes a Straight Line” Warning After Closing a Road

When you’ll see this #

After merging a road’s near-duplicate start/end points to close it — see Fixing “Road Needs Closing” Errors with Close Road Autofix — the Verification panel may show a follow-up message at the newly-closed joint:

[IP4-Start] makes a straight line with [Start-IP1]

Why it appears #

Closing the road creates a small curve at the new joint, because every point on a closed road alignment is required to have one. If the two lines on either side of that joint are already collinear (common right after this kind of merge), that curve ends up with effectively zero length — and the software’s own check for parallel lines correctly notices that the lines either side of it are parallel, and flags it.

What to do about it #

This message is a Warning, not an Error. It does not block generating platforms, slopes, or any other output for the road, so it’s safe to leave in place.

If you’d rather have a fully clean verification list with zero messages, you can follow the message’s own suggestion and manually combine the two lines either side of the joint into a single line.

For other verification messages MiTS can flag, Autofix, or Resolve, see Verification Messages in MiTS.