This blank advanced warning triangle is used to show there is a junction ahead where there is a give way or stop line. This sign is often used when the junction can not be seen on approach and uses supplementary plates to give specific warning to the road user, as per below.
Material: R2/RA2 reflective overlay on aluminium composite backing
2.1.1. The sign to diagram 501 (S2‑6‑1, see Figure 2-1) should be used where the clear visibility distance (see 1.9.3 and 1.9.4) to the STOP or GIVE WAY sign is less than the distance given in Table 2-1. The sign may also be accompanied by the word SLOW (diagram 1024) marked on the carriageway. Where the junction is with a dual carriageway road, the “Dual carriageway” plate remains below the STOP or GIVE WAY plate (see also 5.6). Where there is a gap in the central reservation and a right turn is permitted, this should reduce the risk of drivers turning into the wrong carriageway. See Chapter 3 for further guidance on the STOP and GIVE WAY signs, and Chapter 5 for road markings at junctions.