[throwaway60703]

Also bicycles, motorbikes, e-scooters, trams, trains, runaway objects...

I always thought that the city itself could be part of the swarm system. Roadside sensors could broadcast information to all relevant participants - such as "emergency vehicle incoming, move to the right lane, vehicles ID 123, 456 and 789 stop immediately" or "danger - static object at 45th km", or even "slow down/speed up to 60 km/h to optimize traffic flow".

[cratermoon]

In the science fiction of my youth, where roads or similar systems existed, there were cases where the infrastructure was part of the autonomous vehicle system. It was often car-exclusive, never mentioning pedestrians, mobility devices, or anything that wasn't motorized, but it was an interesting bit of speculation.