The issue about hearing inside cars is made largely irrelevant because cars move at the same speed as other traffic.
In my experience and where I ride, cyclists and velos, generally, move slower than other traffic. This means that they are likely to be frequently overtaken by other traffic so there is a much greater need for a cyclist or velo-rider to know (however the cyclist wants to gain that knowledge) what's coming up behind than there is for a car driver.
I think the whole issue of velomobiles is pretty irrelevant as well, never having seen one on the road I'm not sure that they can be used as any sort of reference point.
That said, I understand that many police motorbikes in London now carry use to move traffic, as they can be heard inside the car and over any internal distractions much easier than sirens.
In my experience and where I ride, cyclists and velos, generally, move slower than other traffic. This means that they are likely to be frequently overtaken by other traffic so there is a much greater need for a cyclist or velo-rider to know (however the cyclist wants to gain that knowledge) what's coming up behind than there is for a car driver.
I think the whole issue of velomobiles is pretty irrelevant as well, never having seen one on the road I'm not sure that they can be used as any sort of reference point.
That said, I understand that many police motorbikes in London now carry use to move traffic, as they can be heard inside the car and over any internal distractions much easier than sirens.