Changed Signals (T1-21)The Changed Signals (T1 21) sign warns motorists of altered or temporary traffic light operations ahead, helping drivers stay alert and adjust their driving safely. It is commonly used in roadwork zones, detours, and intersections where normal traffic light sequences have been modified. Manufactured from yellow CL400 Class 1W reflective material, the T1 21 provides excellent visibility both day and night, ensuring drivers receive clear and early