The green light allows traffic to proceed in the direction denoted, if it is safe to do so and there is room on the other side of the intersection.
The yellow (or amber) light warns that the signal is about to change to red. In a number of countries – among them the United Kingdom – a phase during which red and amber are displayed together indicates that the signal is about to change to green.[3] Actions required by drivers on an amber light vary, with some jurisdictions requiring drivers to stop if it is safe to do so, and others allowing drivers to go through the intersection if safe to do so.