W4 Series — Merge and Lane Change Warning Signs

The W4 Series covers warning signs for merging lanes, added lanes, and lane-change conditions. In temporary traffic control, W4-2 (ADDED LANE) is used when a temporary lane is introduced — such as when a shoulder is opened as a travel lane or when a realigned lane configuration adds an approach. These signs help drivers anticipate a change in the number of available lanes before reaching the transition.