That’s the compression, same story in factorio. Before/after compression it’s static, so you can avoid having to update any value.

The main difference from factorio belts I think is actually in the insertion — if there’s no room in the belt, insertion is blocked; whereas I’d expect a car to “slip in”.

But I think you can still say that maintains the property that a compressed belt will always be compressed, excepting insert/removal; and insertion/removal just requires updating a static number of deltas (2, in the middle of the line, 1 at the end of it)