Roadside Safety - Sideslope Improvements
Sideslope improvements include measures to reduce the gradient of the embankment or roadside slope adjacent to the carriageway and also the removal of any hazardous objects that are located within that area.
Sideslope improvement will reduce the likelihood of a vehicle rollover in run-off road/loss of control crashes and may also reduce the severity of these types of crashes. Generally flatter sideslopes are safer. A sideslope is considered to be traversable if an errant vehicle can recover and return to the roadway while keeping all wheels in contact with the ground.
If the slope cannot be made traversable and clear of hazards, it should be protected (for example, with the use of safety barriers). In these cases, the geotechnical properties of the sideslope material (soil, rock etc.) should be considered.
- Sideslope improvement will reduce the likelihood of rollover in a run-off road/loss of control crash and may also reduce the severity of these types of crashes.
- Flatter sideslopes are generally less likely to erode.
- The cost of providing a traversable slope may be less than the cost of stabilising and maintaining steep slopes.
- Sideslopes should be free of hazards and objects that may cause vehicle snagging.
- On downward slopes, a clear run-out area may also be required at the base of the slope.
- The provision of traversable sideslopes may require the removal of native flora, which can result in erosion, sedimentation of waterways and removal of animal habitats.
- The provision of traversable sideslopes may have property impacts and require extensive land acquisition.
- Extensive filling of side slope will increase the footprint of the road with potentially high environmental impacts. However, suitable grading and contouring can reduce the impacts and better integrate the road with the surrounding areas.
- The practicality of side slope improvements is influenced by local terrain conditions and availability of materials.
- In areas where the sideslope transitions from an upward slope to a downward slope (and vice versa), the rate of change in gradient of the crossfall should be gradual to ensure that the sideslope can be traversed.
The Star Rating Demonstrator is a freely available tool with the iRAP online software, ViDA. With the Star Rating Demonstrator, it is possible to explore the impact that this Safer Roads Treatment has on risk.
Treatment Summary
Costs | Medium |
Treatment life | 20 years + |
Potential casualty reduction | 10-25% |
Case Studies
