Warning lights must be no more than 1.5 metres above the road for speed limits of 40 mph or less, and no more than 1.2 metres above the road for speed limits of 50 mph or more. In terms of body colour, lamp colour, flash rate and steady light performance, etc. warning lights must conform to the TSRGD (TSR (NI) in Northern Ireland).
| Warning lights | Lights can be used | Lights must be used | |||
|---|---|---|---|---|---|
| Speed limit | 20 mph | 30 mph | 40 mph | 50 mph | 60 mph |
| Maximum height | 1.5 m | 1.5 m | 1.5 m | 1.2 m | 1.2 m |
| Flashing option permitted? (on street lit roads only) | Yes | Yes | Yes | No | No |
