^What I know of hvac on both rail and bus makes me think that it’s the exact reverse of what one would want to minimise exposure to an airborne virus. Most vehiches distribute heated/cooled air throughout the vehicle, ie there are a fresh air ports near each seat. But the return air ducts are central. That’s great for AC ,(and window defrosting) but in covid space it means every passenger’s breath is pulled the length of the vehicle, ie through everyone’s airspace, before it is extracted.
I’m not knowledgeable whether/how air is recirculated and filtered, but to minimise transmission, it should not recirculate.
It strikes me that in covid space one would want each passenger’s breath to be removed as close to that passenger as possible, without taking a trip through the vehicle. Push air pressure in somewhere to maintain a positive internal pressure, and push the air out of the vehicle at every seat. Effectively, a transit vehicle should be a very leaky balloon. Maybe one just reverses air flow from present.
Or, people bring their own SCBA, or a mask that plugs into a central air supply ;-)
I suspect that transit experts are hoping for a vaccine so that new designs aren’t needed. Cleaning vehicles more rigourously is great news, but I suspect that so long as people fear closeness to other people, public transit will remain a non starter for most.
- Paul