Not quite MRM, different forces have different driver grades.
In my old force there were 3 driver grades
Basic: No blue light jobs, could only stop vehicles using blues and twos, no exceeding speed limits.
Response: As the name suggests, responding using Blues and Twos, could pursue cars if it was authorised by Control Room Insp and road conditions dictated it was safe to do so.
Advanced: Traffic.
But as MRM says, when the orange button was pressed, all bets are off, a fellow bobbies life was in danger, although you took your life into your hands if you exxeded your driving ticket.
Aopolgies for a techie posting on a water fairies forum, but I saw one of the old Range Rover Rapid Intervention Vehicles today, with civvie plates on, non fire service. Haven't seen one since I drove one when on Fire Piquet(sp?) at Colt in the early 90's.