Major and minor roads include interstates; state and US highways; county, local, private, residential, and seasonal roads; and trails. Contaminants from vehicles and activities associated with road and highway construction and maintenance are washed from roads and roadsides with rain or snowmelt and can seep into ground water or run off directly to surface water bodies. Contaminants can include herbicides from right-of-way treatment, road salt and road salt anti-corrosives, anticaking additives, automotive fluids, and fertilizers. Major roads pose an additional threat from the potential for large volume spills of materials contained in tankers and semi-trucks.