Department for Transport circular 01/2007 provides guidance to local authorities on the deployment, visibility and signing of speed and red light cameras. This came into effect on 1 April 2007 and recommends the use of camera warning signs where permitted and practicable. The signing is contained in the Traffic Signs Regulations and General Directions (TSRGD) and its use is not mandatory. However, in order for a speed limit to be enforced all speed limit signing must be lawful and correct and in accordance with TSRGD. The guidance was placed in the Library of the House and is also available on the Department's website.