Emergency vehicle equipment in the United Kingdom

This usage is colloquially known as "blues and twos", which refers to the blue lights and the two-tone siren once commonplace (although most sirens now have a range of tones like Wail, Yelp, Phaser, and Hi-Lo).

From 1993-1998 a television documentary following Britain's emergency services was titled Blues and Twos for this reason.

Provision exists for a national standard to be required in order to utilise speed limit exemptions, but this has not been brought into force.

In the UK, vehicles used for certain purposes may have exemptions from some road traffic regulations whilst responding to an emergency.

Merely being authorised to use blue lights and sirens does not of itself grant exemptions from road traffic law.

An Incident Response Unit operated by Norfolk Fire and Rescue Service with a blue lightbar on top, alternately flashing LED lights on the front, and flashing headlights. This vehicle is part of the New Dimension programme and consequently does not carry any insignia of Norfolk Fire and Rescue Service .
Electronic sirens have replaced two-tone horns on most emergency vehicles
Six Metropolitan Police Service motorcycles driving with the blues and twos on. They can be seen breaking a number of normal traffic rules. Each motorbike has driven through a red light, and the motorbike on the far right can be seen driving on the wrong side of the road and passing on the right of a keep left sign.