3 Risk assessment/ALCAM
3.3 Assessment of level crossings
Appendix DC and Appendix DD provide a detailed list of characteristics, controls and accident mechanisms used in ALCAM. The following briefly describes some of the more critical elements that must be measured for input into the model.
3.3.1 Level crossing geometry and environs
The geometry and environs elements include:
- number of operational railway lines, including shunting lines
- number of traffic lanes each way – view along the railway line could be obstructed by traffic in adjacent lane
- grade on each approach to the railway line(s) – critical when the railway forms a ‘hump’ in the road affecting the passage of heavy and long vehicles across the railway lines
- skew of the road to railway line – view along railway line affected by degree of skew
- proximity to sidings, road intersections and other traffic generation.
3.3.2 Traffic characteristics
Traffic characteristics recorded include:
- volumes, by categories, of road vehicles, pedestrians and rail vehicles
- operating speeds of these users.
3.3.3 View lines/visibility
Much of the data described above are essential inputs into calculation of the view lines required at the level crossings for both drivers and pedestrians.
For drivers, there are two critical view lines considered:
- the restart view line, which is the minimum distance along the railway line(s) from the driver's eye position in a vehicle at the stop line position of the closest railway line required to allow the driver to start from a stopped position and clear the railway line before a train arrives
- the road approach visibility, which is the minimum distance along the railway line(s) from the level crossing that either:
- a driver is able to see a train and stop before reaching the level crossing; or
- a driver continues at the approach speed and crosses the level crossing safely ahead of a previously unseen train or a train far enough away to be clearly not a collision threat.
The best possible views must be maintained at level crossings. Appendix B details the formulae used in determining the views required utilising a range of relevant driver, vehicle, road and rail parameters.
