Road Narrows on Left Permanent Post Mounted Sign - Dia 517 R2/RA2 (Face Only)The road narrows on the left sign to diagram 517L gives an advance warning of the road narrowing on the left (current) side. This means the thinning of the route creates a potential hazard because you will have to drive closer to oncoming traffic. If the narrowing doesn't remove a lane from the junction and the lane does not have a severe taper, the sign isn't needed. Table 4 1 on page 19 of the Traffic Signs Manual, Chapter 4 covers the specific