Junction (road)
From Wikipedia, the free encyclopedia
A road junction is a location where vehicular traffic can change between different routes or directions of travel.
[edit] 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.
[edit] Modern junctions
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.
[edit] Intersection vs. 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.
| Types of road junctions | |
| Interchanges (grade separated) | Cloverleaf - Diamond - Directional T - Diverging diamond Parclo - Trumpet - SPUI - Stack - Three-level diamond |
| Intersections (at-grade) | Box junction - Continuous flow - Crossroads - Hook turn - Jughandle - Michigan left Quadrant roadway - Roundabout - Superstreet - 3-way junction - Traffic circle |
