Mythbusters: blues 'n' twos & teabreaks
Popular misconceptions of policing: when a police car goes through a red traffic light on blue lights and 2-tone "audible warning signal" only to stop both immediately upon getting to the other side of the junction, the officers within that car are late for their dinners, and are just trying to make better progress towards the holy kebab.
Truth: when a call comes through on the radio, different units volunteer for that call if they are free, often several units per call, especially if it is an "I" call (I="immediate", ie get there quickly - someone is in danger or some offence is in progress and there is a realistic chance of doing some good by getting there asap). This is called "putting up" for a call. The radio controller assigns the several units and whoever gets there first assesses whether other units (officers OR cars are counted as "units") are still needed to attend. The radio communication might go, "Cancel any further to Letsbe Avenue", "Full cancellation" or, occasionally, the slightly less professional addition, "it's L.O.B."*
The marked police unit, now having no need or justification for speeding through junctions, treating red traffic lights as Give Way, proceed-with-caution signs any more, cancels the blue lights and 2-tones and reduces to the regular level of speed and driving proficiency of the rest of the driving public (ie probably too fast, on their mobiles, no seat-belts and up the car in front's bum-hole).
And if there happens to be a nice cup of tea and a kebab at the end of that journey, all's well and good, but the officers you've just slagged off were probably diverting from the highlight of the day - REFS! - in order to take the emergency call in the first place, so leave them alone! Grr...
* LOB = silliness, inconsequential trifle.