Explanation: At some junctions, there may be separate signals for different lanes. These are called 'filter' lights. They're designed to help traffic flow at major junctions. Make sure that you're in the correct lane and proceed if the way is clear and the green light shows for your lane.
Category: Road and traffic signs
References: The Official DVSA Guide to Driving: Section 6, Highway Code: Page 102, Know Your Traffic Signs: Page 119
