Risk Assessment | Bridges | Safety barriers | Trains
A rail bridge passes over a road at an angle, with its collision protection beams parallel to the bridge. Skewed crash beams are discouraged by some authorities due to concerns about shunting loads into adjacent areas.
Four options were assessed. This was done by first undertaking a literature review on collision protection beams and their angle. No source materials on the issue of ‘skew’ and the ‘subsequent risks’ were found, therefore it was assumed that the general guidance from authorities is based on assumptions, combined with some collective industry experience. Important gaps in knowledge or guidance appears to include:
- What angle of skew, and operating speed, is likely to deflect a load laterally any distance of significance?;
- What’s the estimated lateral deflection distance?;
- Apart from vulnerable road users on adjacent paths / areas, is the consequence of displaced loads into opposing carriageways any greater than into the ‘crash’ carriageway?; and finally,
- What constitutes a ‘compliant’ beam.
Likelihood of impact was assessed by examining: truck types, volume, road class, bridge height clearance, crash data, likelihood of ‘shunt’ occurring due to skew, and approximately 20 other common road risk factors. Severity factors were then assessed.
The analysis concluded that there were no obvious indications that this is a high risk site requiring reorientation of the skewed CPB to parallel-to-road.
