| 摘要 |
<p>A swing beam 12 is suspended from a frame formed of two side columns 11, with reinforcing buttresses 13, and a top bar 10. The swing beam 12 is positioned at a height to prevent the passage of vehicles over a predetermined height, thereby protecting a reduced clearance structure such as a bridge or tunnel further along the road. The beam 12 is biased to its vertically suspended position by springs 14 which resist the deflection of the beam under impact. The springs 14 may be disposed with a system of levers which increase the force applied to the beam as it is swung away from its default position. A system of ropes 15, operated by a winch 16, is used to lift the beam 12 clear of a vehicle following an impact in order to facilitate the vehicle's removal.</p> |
