Infantry Drills

D-41: Turning or Deceleration Zone

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D-41. The search element establishes obstacles and an overwatch force to control each road or traffic lane being blocked. The turning or deceleration zone forces vehicles into making a rapid decision. The vehicle can decelerate, make slow hard turns, or maintain speed and crash into a series of obstacles. The road or traffic lanes should be blocked by means of obstacles positioned at either end of the checkpoint. (See appendix H of this publication for a discussion of obstacles.) These obstacles should be such as to be quickly and easily moved in case of emergencies. They should be sited so as to extend the full width of a traffic lane and staggered to force vehicles to slow to negotiate an ‘S’ turn. (See figure D-9, page D-18.) Stop signs also should be erected ahead of the obstacles and at night illuminated by means of a light or lantern.

D-42. Ensure vehicles are stopped facing an obstacle (berm, tank, or wall) capable of stopping a slow moving truck. Some obstacles will have to be improvised. Examples of these include:

  • Downed trees.
  • Beirut toothpick– nails driven through lumber.
  • Caltrops placed across the road.
  • Debris, rubble, large rocks.
  • Abatis.
  • Road cratering.
  • Dragon’s teeth, tetrahedrons, concrete blocks.
  • Mines.
  • Prepared demolitions.
  • Concertina wire.
Figure D-9. Controlling vehicle speed through obstacle placement and
serpentine placement

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Go Back To: U.S. Army FM 3-21.8: The Infantry Rifle Platoon and Squad