Additionally (I still love roundabouts) there can be a max-wait-time problem when there is heavy traffic in one direction.
If a basketball game ends there can be 20,000 cars bumper-to-bumper trying to leave. Let’s say (looking at a map) they’re going left-to-right through an intersection.
If there’s 1 car trying to go top-to-bottom…
- If the intersection is a stoplight it doesn’t matter. Even if there were 20 million left-to-right cars; it’s still a 5 or 10min wait for the top-to-bottom car.
- If the intersection was a stop sign it also doesn’t matter; it’ll be the left-to-right cars turn then the top-to-bottom cars turn
- At a roundabout though (at least in the US), vehicles entering on the left always take priority over vehicles entering from the bottom. So the top-to-bottom guy could be there all night
Game days on my campus can cause a 2 hour wait on a 1 mile road. My campus is unusual, but just FYI absolutely insane wait times do happen regularly in some cities.
Yeah I think scribbling out the 30% with a 100% and saying “roundabouts” would make for a pretty good punchline. I figured I’d get complaints about AI being quick and low cost compared to road construction, which is why I ended up going with the “bikes” punchline instead.