Single Carriageway Ahead Permanent UK Road Sign
- Post Mountable with 2 fixing rails
- Class 2 R2/RA2 Reflective
- Available in 450mm, 600mm, 750mm, 900mm Tri
This sign allows road users to be prepare to merge both lanes of a dual carriageway into a single carriageway. Often placed directly before a two way traffic sign to further emphasise the change in road layout. Diagram 520 has no variations.

Specification:
Material: R2/RA2 reflective overlay on aluminium composite backing
Fixing Method: 2 fixing rails for post mounting
Reflectivity: Class 2 R2/RA2
As per the UK Highways Traffic Sign Manual Chapter 4 - Warning Signs page: 29 The following advice is given:
5.1.1. The signs to diagrams 520 (S2‑2‑15, see Figure 5-1) and 521 (S2‑2‑16, see Figure 5-2) indicate the resumption of two-way traffic on a single carriageway road after a length of dual carriageway and, in the case of diagram 521, after a one‑way road. The sign to diagram 522 indicates a two‑way road crossing ahead (S2‑2‑17, see Figure 5-3 and 5.2.2).