One important strategy for holding down roadway maintenance cost is to properly control weed and vegetation growth along a highway.
Safety is a high priority at WSDOT. Vegetation, if left alone can grow out of control, blocking visibility (signs, traffic, wildlife) which could endanger motorists. Weeds must be controlled to avoid impacts on agriculture and native ecosystems. Pride of ownership and the beauty of Washington State are also important reasons why we try and manage roadside vegetation.
Traditionally we have used herbicides as one of the primary tools for roadside vegetation management. But the latest WSDOT Grey Notebook (December 2006) shows that we continue to reduce the amount of herbicides used, while still accomplishing our roadside maintenance goals.
In 2002, we used approximately 120,000 pounds of herbicide statewide maintaining vegetation. In 2006, that number dropped to just more than 40,000 pounds of herbicide statewide.
The majority of this reduction is the result of our effort in eastern Washington to minimize the area of vegetation-free ground along the edge of the highway pavement.
Last year, we adopted restrictions above and beyond federal and state legal mandates for herbicide usage. In addition, WSDOT is continuing to refine its policy and practices for vegetation management through an ongoing research project by the University of Washington. The study includes field trials on alternate vegetation control methods.