Traffic Merges on to Main Carriageway Sign Diagram 509.1 RA2 Post Mountable Size:450mm Tri As per the UK Highways Option:3 4" (19mm) Buckles x100 As per the UK Highways Traffic Sign Manual Chapter 3 Regulatory Signs page: 23 The following advice is given: diagram 501 with the appropriate distance plate should be used traffic merges on to main carriageway ahead sign is used to warn road users that the road they are travelling on is going to merge onto a main carriageway ahead These signs may be used only in situations where the traffic stream joining from a slip road crosses a road marking to diagram 1010 and is required to concede priority to any through traffic