The roadside hawk is long and weighs . Males are about 20% smaller than females, but otherwise the sexes are similar. In most subspecies, the lower breast and underparts are barred brown and white, and the tail has four or five grey bars. Twelve subspecies are usually recognised and there is significant plumage variation between these. Depending on the subspecies involved, the roadside hawk is mainly brown or grey. It is fairly common to observe a touch of rufous (i.e., a light reddish-brown) on the bird's wings, especially when seen in flight. Its call is a very high-pitched piercing squeak. The eyes of adult roadside hawks are whitish or yellow. As suggested by its specific name, its beak is relatively large.
