In this chapter, we show that roads may have positive, neutral, or negative effects on the plants and vegetation remaining on roadsides or planted on roadsides. Effects vary with road width, traffic volume, and the slope, soil, hydrology, and nature of the surrounding landscape and plant communities. Positive effects include the protection of rare habitat types and plant species from transformation to crops, mines, housing, and industrial areas, protection from over-grazing, and provision of dispersal corridors. Negative effects of roads on plants are many and include direct damage to plants and habitats, facilitation of access to illegal plant harvesters, pollution of plants and their substrate by heavy metals, salt, dust, and fuel spills, as well as facilitation of invasive alien environmental weeds. Management of roadsides may either mitigate or exacerbate the negative effects of roads on plants, or even potentially multiply the beneficial effects, such as preserving rare species and generating seed banks. Roadside plant population remnants and seed banks could contribute to ecological restoration under a scenario in which modern life is made ecologically sustainable through reduced fossil fuel consumption and investment in greening and ecological restoration.