Australia has over 874,000 km of roads which translates to 1.75 million km of roadsides with vegetation that must be managed. Roadsides can be a harbour for important weeds and a potential avenue for their spread.

Weeds on roadsides are divided into legally controllable or ‘declared’ weeds and ‘other’ weeds.
‘Other’ weeds have no legal requirement for control and are generally seen as a low priority for roadside vegetation managers.
Agricultural weeds on roadsides are low priority and are only targeted for road user safety (line-of-sight) or if on a locally important weed list developed by a local natural resource management group or council.
While each state has a slightly different approach to managing roadside vegetation, major roads are the responsibility of the state roads department and minor roads are the responsibility of local government.

Table 1. Length of Australian roads by type – 2015 (BITRE 2017)

Managing roadside vegetation is complex

Managing roadside vegetation can be complex due to:

a priority of road-user safety
the need to maintain road structure
fire management
control of declared weeds
protection of rare and endangered vegetation
Roadside vegetation management is complex because they are managed by a range of organisations which often use contractors and have limited budgets.

Public safety is the primary driver for roadside vegetation management. An extended line of sight, unimpeded vision of guideposts, signs, railings and the ability for a vehicle to get off the ‘road’ without any damage to people and/or vehicles are important goals.

The maintenance of infrastructure is also an important driver of roadside vegetation management. It is essential that water freely flows from the sealed surface and off the road shoulder. Ponding of water near the edge of the seal caused by weed growth allows water to enter the road base, which in turn destabilises the underlying road structure. Corrosion and potential fire damage to roadside posts and signs can be reduced by keeping them free of plant growth.

Fire management can play a significant role in how roadside vegetation is managed. Roadsides are a point of ignition, provide containment and firebreak, and are a route of escape in the event of an evacuation. In New South Wales and Western Australia roads can be used as fire breaks, so the road corridor tends to be wider than in other states. For example, in Western Australia major roads will have a 4 to 10 m vegetation management buffer from the edge of the bitumen.

Another increasing complication is that many of the weeds have developed resistance to, or were never controlled (tolerant) by, commonly used herbicides such as glyphosate.

Control of weeds on roadsides

Weeds on roadsides are divided into legally controllable or ‘declared’ weeds and ‘other’ weeds. ‘Other’ weeds have no legal requirement for control and are generally seen as a low priority for roadside vegetation managers. Agricultural weeds on roadsides fit into the ‘other’ category and are low priority. They are only targeted for road user safety (line-of-sight) or if on a locally important weed list developed by a local natural resource management group or co