What do you particularly mean by ignore?

Because my issue could be it or related.

I mean when e.g. you've set up timed traffic lights then saved game and after next load vehicles ignores your settings and behave like there were no traffic lights set.
Check out issues page on github[github.com] there are plenty of issues. You can add yours if you wouldn't find similar and track development progress ;)

Well, I found out what was causing my problem - it was the "priority rules at junctions with timed traffic lights" policy. Whoops!

I'm happy you resolved the problem

I've found something related; I gave a busy junction (six - eight lane roads) slip lanes, which resulted in a very short segment at the intersection. I set up a timed light but vehicles continued to drive through from both sides. The segments were short enough that they held about 2 vehicles before the cars backed into the slip-lane "intersection", and I used the lane connector, if that helps.