NPSBS - Non-Proprietary Safety Barrier Systems (UK).
TCB is approved to EN1317 as N2 W6 single and double sided with post spacing at 3.2m. This corrugated steel beam is mounted onto 'Z' shaped posts and is most frequently used on UK highways. TCB absorbs impact by deflecting as a whole and assists the vehicle to decelerate, whilst guiding it back towards the carriage-way.
Open Box Beam (OBB) is approved to EN1317 as N2 W4 and N2 W5 single and double sided with post spacing at 1.2m and 2.4m respectively.
The strength of this barrier system lies in the 4.8 and 2.4m lengths of rail supplied. These are connected together by fishplates which match the profile of the rail and sit inside, bridging adjoining beams. Heavier duty 'Z' section posts are used for mounting OBB double height format (DROBB), where potential hazards exist for larger vehicles.
The TCB system is best applied on straight runs and shouldn't be installed on a radius less than 120m. Despite there not being a maximum installation lengths, the approach and departure ends must be anchored at ground level to heavy duty end posts/full height anchors.
The M24 bolts and special steel brackets fitted act as tensioner units and are located at 70m intervals along the length of the barrier.
Again, there is no limitation on the length of barrier; however, approach and departure ends should be mounted onto strong SHS posts, or to full height anchor frames.
A special expansion assembly must be fitted every 100m on the OBB to allow for the rigid nature of this profile and effects caused by temperature changes.
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