there are even more (small) problems with riding on belts, eg when starting to go on a belt, green and white arrows behave differently: when using green arrows we need to put a green arrow under the first tile of the belt so that the arrow in front of the belt can move the cart onto the belt, but when we use white belts and have one white arrow in front of the belt and another under the first tile of the belt, the cart (not sure whether that applies always, but at least most of the time) stops moving by itself and only rides the belt passively instead of driving on the belt.
why does this happen? maybe at an arrow under the start of the belt the carts old command is cleared and the new command would be activated on the next tick, but on a belt it already has moved and thus the "drive offroad" is not set again, making the cart go slow on the belt?
a workaround is simple: don't use green arrows in connection with belts. to get the best speed you need to use white arrows anyway, and thus there is no need to ever have any arrows under a belt, neither at the start nor at the end.
but Verhofin is right: something should be done so that recovering carts is easier. they too easily can get stuck between tiles when moved across a belt. and similar problems exist when carts hit an obstacle (the player, or a power pole etc), thus stop outside the tile grid and cause accidents, with up to a dozen or more carts being squeezed together.
I also think that improved speed (either from belts or from floor bonus) is nice (and would look great when carts drive faster on roads) but it's not really needed. it improves travel times and thus less carts are needed for a route, but for the throughput "spacing of carts times speed" is important, and won't be improved much when carts mostly have a 1+ second gap between them so that higher speed causes larger gaps and thus doesn't change throughput a lot.
