>>1466184Double-deckers have to intrinsic bottlenecks, the first one being the stairs that are usually narrow, the second one being the doors, especially when compared to an articulated bus with 4 to 6 doors.
This leads to longer stopping times, which is suboptimal for routes within a city.
For long distances, this is negligible, with the two deck structure enabling more comfortable rides, for example by having an undisturbed view of the road ahead or less crammed toilets.
