A junction, when discussed in the context of transport, is a location where traffic can change between different routes, directions, or sometimes modes, of travel. Historically, many cities and market towns developed wherever there was a junction. A road intersection offered opportunities for rest or trade for travellers and merchants. Towns sprang up to accommodate this; the first such in Europe were probably at intersections of the Roman roads. Junctions also developed where different modes of transport intersected, e.g. canal and rail.