Lanekind
A GREEN ARROW may be provided in addition to the full green signal if movement in a certain direction is allowed before or after the full green phase. If the way  is clear you may go but only in the direction shown by  the arrow. You may do this whatever other lights may be showing. White light signals may be provided for trams

lanekind.co.uk/road-signs/traffic-light-signals/a-green-arrow-may-be-provided-in-addition-to-the-full-green-signal-if-movement-in-a-certain-direction-is-allowed-before-or-after-the-full-green-phase-if-the-way-is-clear-you-may-go-but-only-in-the-direction-shown-by-the-arrow-you-may-do-this-whatever-other-lights-may-be-showing-white-light-signals-may-be-provided-for-trams

Light signals controlling traffic · Traffic light signals

A GREEN ARROW may be provided in addition to the full green signal if movement in a certain direction is allowed before or after the full green phase. If the way is clear you may go but only in the direction shown by the arrow. You may do this whatever other lights may be showing. White light signals may be provided for trams

One of 5 signals the Highway Code files under traffic light signals. The other 4 are at the foot of this page.

Category
Light signals controlling traffic
Group
Traffic light signals
Address
/road-signs/traffic-light-signals/a-green-arrow-may-be-provided-in-addition-to-the-full-green-signal-if-movement-in-a-certain-direction-is-allowed-before-or-after-the-full-green-phase-if-the-way-is-clear-you-may-go-but-only-in-the-direction-shown-by-the-arrow-you-may-do-this-whatever-other-lights-may-be-showing-white-light-signals-may-be-provided-for-trams