when allowing a car to start a turn. It causes
https://github.com/dabreegster/abstreet/pull/276#discussion_r470269394
and also the lakeslice scenario to gridlock (a regression that began a
few weeks ago). But keep the flag on for now, to keep the montlake
scenaro running at least.
https://dabreegster.github.io/abstreet/trafficsim/gridlock.html has
notes about the many different causes and in-progress fixes for
gridlock. This experiment hasn't been explained very well yet, but
roughly it treats a cluster of traffic signals as one, so that once a
vehicle gains access through the first light, they guarantee immediate
access through the entire sequence. This interacts with the "don't block
the box" behavior (don't start a turn if you might get stuck in the
intersection) strangely.
While attempting to get this rollback to work, I also had to manually
redraw the traffic lights for a few manually specified intersections.
They became out-of-date a few weeks ago when I cleaned up the OSM
geometry upstream and the referenced IDs changed, and I hadn't bothered
to re-time the signals. Luckily, with the new multi-signal editor,
redrawing the timing was much easier than originally!
Regenerated all data and lots of bus routes vanished. Plan to get back
to that project soon.
