Notes for Figure 6H-17—Typical Application 1Mobile Operations on a Two-Lane Road



  1. Vehicle-mounted signs shall be mounted in a manner such that they are not obscured by equipment or supplies. Sign legends on vehicle-mounted signs shall be covered or turned from view when work is not in progress.
  2. Shadow and work vehicles shall display high-intensity rotating, flashing, oscillating, or strobe lights.
  3. If an arrow board is used, it shall be used in the caution mode.



  1. Where practical and when needed, the work and shadow vehicles should pull over periodically to allovehicular traffic to pass.
  2. Whenever adequate stopping sight distance exists to the rear, the shadow vehicle should maintain the minimum distance from the work vehicle and proceed at the same speed. The shadow vehicle should slow down in advance of vertical or horizontal curves that restrict sight distance.
  3. The shadow vehicles should also be equipped with two high-intensity flashing lights mounted on the rear, adjacent to the sign.



  1. The distance between the work and shadow vehicles may vary according to terrain, paint drying time, and other factors.
  2. Additional shadow vehicles to warn and reduce the speed of oncoming or opposing vehicular traffic may be used. Law enforcement vehicles may be used for this purpose.
  3. A truck-mounted attenuator may be used on the shadow vehicle or on the work vehicle.
  4. If the work and shadow vehicles cannot pull over to allow vehicular traffic to pass frequently, a DO NOT PASS sign may be placed on the rear  of the vehicle blocking the lane.



  1. Shadow vehicles are used to warn motor vehicle traffic of the operation ahead.



  1. Vehicle hazard warning signals shall not be used instead of the vehicle’s  high-intensity rotatingflashing, oscillating, or strobe lights.
  2. This typical application shall not be used on State highways, Department of Transportation’s Standard Plan T17 for moving lane closure shall be used instead. See Section 1A.11 for information regarding this publication.