only has traffic weaving in and out from one side. This is one of the big reasons why single rider motorcycles are always allowed in carpool lanes. They are much less likely to be sideswiped or cutoff by inattentive drivers there.

The laws are very deliberately written to allow extended travel in the carpool lane regardless of speed. They are also deliberately written to disallow extended travel in the passing lane unless you are passing (or prevented from passing by the car in front of you when all lanes are congested).

The carpool lane is rarely the fastest lane except during rush hour. Buses are perhaps the most deserving of that lane, and they almost never travel faster than the posted speed limit. The laws relating to carpool lanes make it very clear that it is intended to be a safer, lower stress extended travel lane.