Controlling and maintaining roadside vegetation can reduce maintenance, and significantly improve driver safety. It improves sight distances around corners, and approaching bridges and intersections, and creates a wider road for passing traffic. Design sight distances must be maintained over the period of operational use of the road. This is a requirement of WorkSafe’s Approved Code of Practice for Safety and Health in Forest Operations.
Overgrown vegetation tends to shade the road, especially during winter. This increases the risk of pavement damage, because it prevents the road surface from drying, and will increase ice in areas prone to freezing. Also, road obstructions, such as fallen trees and overhanging branches, will hinder access, create a safety risk, and cause drainage structure damage as vehicles move off the running surface to avoid the vegetation.
Too much vegetation in ditches will reduce water flow, and possibly create dams and washouts, or other maintenance problems. For example, culverts and ditches can be damaged because machinery operators cannot see the culvert ends because of vegetation growing in them.
Ditches can be mowed or sprayed. Most roadside vegetation maintenance needs to be completed during spring and summer, because this is when vegetation grows fastest. However, care should be taken not to eliminate all vegetation from the ditch, or scouring could result. Be careful of fire risk. Mowing can create fires due to sparks from stones and mower blades. Dried vegetation can increase the roadside fire risk.
If the roadside scrub gets too large, it can be a challenge to remove it efficiently. Roadside flails or mowers can generally cut material below 100 mm in diameter, so maintenance should be completed before vegetation reaches this stage.