In the field of road transport, a road junction is a place where two or more roads either meet or cross. The main types of road junctions are intersections and interchanges. A road junction may also be called a crossroads. A junction between 3 road segments (arms) is a T junction (two arms form one road) or a Y-junction.
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4 Types of interchanges between two freeways
5 Types of interchanges between a freeway and a non-freeway road
Note: The descriptions of road junctions are for countries, like the United States, where vehicles drive on the right side of the road. For countries where they drive on the left, the junctions are the mirror image (the same except that right and left are reversed).
A ramp is a short section of road which allows vehicles to enter or exit a freeway (motorway).
- A directional ramp always tends toward the desired direction of travel.
- A non-directional ramp goes in a direction opposite to the desired direction of travel. Many loop ramps (as in a cloverleaf) are non-directional.
- A semi-directional ramp exits a road in a direction opposite from the desired direction of travel, but then turns toward the desired direction of travel. Many 'flyover ramps' (as in a stack) are semi-directional.
IntersectionsAn intersection is a road junction at which roads meet at grade. Types of intersections include:
- Uncontrolled intersections, without signs (or sometimes with a warning sign). On a 4-way intersection traffic from the right has priority; on a 3-way intersection rules may vary by country: either traffic from the right has priority again, or traffic on the continuing road. For traffic coming from the same or opposite direction, that which goes straight has priority over that which turns off.
- Yield-controlled intersections may or may not have specific "YIELD" signs (known as "GIVE WAY" signs in some countries).
- Stop-controlled intersections have one or more "STOP" signs. Two-way and four-way stops are common.
- Signal-controlled intersections depend on traffic signals, usually electric, which indicate which traffic has the right-of-way at any particular time.
- A traffic circle is a special type of intersection at which traffic streams are directed around a circle. Types of traffic circles include 'roundabouts', 'mini-roundabouts', 'rotaries', "STOP"-controlled circles, and signal-controlled circles.
InterchangesA highway interchange is a road junction that utilizes grade separation, and one or more ramps, to permit traffic on at least one road to pass through the junction without crossing any other traffic stream. A complete interchange has enough ramps to provide access from any direction of any road in the junction to any direction of any other road in the junction. A complete interchange between two freeways requires 8 ramps. A complete interchange between a freeway and another road (not a freeway) requires 4 ramps.
Types of interchanges between two freeways
Types of interchanges between a freeway and a non-freeway road