It’s largely filled with letters and maybe small packages (e.g., my coffee subscription). Anything larger than a large book seems to still be delivered by someone driving a van. The trikes roam the streets going door to door, the vans operate more like a courier service.
That, and also the post offices in towns are pretty close. In my area that means there's 4 of them, around 1km apart. Covering probably 20k people in the town itself + another 10k in the general area.
