an ambulance. In the UK, it is known as an RV or RRV (rapid response vehicle). It is sent to 'red' and 'purple' calls where the call taker has determined that an 8 minute response time is required as the incident is immediately life threatening.
It carries the same medical equipment and medication as is carried on a front line ambulance - but no stretcher or spinal immobilisation gear.
RRVs are occasionally used to transport patients. If we decide a patient needs to go to hospital, we can transport some of them in the back of the RV if they don't need to be 'attended' (i.e. no ongoing intervention or monitoring).
The ambulance service in my area generally use Skoda, Ford or Volvo cars as RRVs - but I'd love to drive one of these as well as my own. It would be interesting to drive one at speed routinely without running the risk of getting a ticket