Junction (road)

An intersection of roads.

A road junction is a location where vehicular traffic going in different directions can proceed in a controlled manner designed to minimize accidents. In some cases, vehicles can change between different routes or directions of travel.

Origins

Roads were initially built as rights of way to link locations of interest: towns, forts and geographic features like fords. As a result, many such locations formed the meeting point of such roads and they became the first road junctions. Where roads met outside of town, these junctions provided an attractive point to build a new settlement, such that they could receive passing trade from both directions. Scotch Corner is an example of such a location.

Junction names

Junctions are often named to help travelers navigate road networks. Names can be assigned by geographic location of the junction, or the name or direction of the connecting routes.

In some cases, particularly in the United Kingdom, a junction could become known by the name of a notable pub located at the intersection. Pubs were often located in junctions to maximize passing trade, and the junctions became known by the name of the pubs, even in cases where the pub was later demolished.

Other junctions may be named after local natural or man-made features.

Further information: List of road junctions in the United Kingdom

Modern junctions

Intersection along the Veterans Memorial Parkway, an at-grade expressway in London, Ontario.

However, with the 20th century advent of road traffic, roads became much busier and junctions became clogged with vehicles unable to cross each other's paths. In modern practice, bypasses and ring roads are used to keep through traffic out of major population centres.

In some countries that have right-hand traffic, a right turn on red is permitted at traffic lights in order to reduce waiting times. It can be implemented either by allowing the vehicles to turn right by using the give way rule, or by providing a separate lane connecting the two perpendicular roads and avoiding the junction entirely.

Conversely, some countries with left-hand traffic use a left turn on red rule.

Intersection versus interchange

There are two different types of junction between roads.

• Interchanges are junctions where roads pass above or below one another, preventing a single point of conflict by utilising grade separation and slip roads. The terms motorway junction and highway junction typically refer to this layout.
• Intersections do not use grade separation (they are at-grade) and roads cross directly. Forms of these junction types include Roundabouts and traffic circles, priority junctions, and junctions controlled by traffic lights or signals.