or more of the roads is not disrupted. Instead of a direct connection, traffic must use on and off ramps (United States, Australia, New Zealand) or slip roads (United Kingdom, Ireland) to access the other roads at the junction. The road which carries on through the junction can also be referred to as grade separated. Typically, large freeways, highways, motorways, or dual carriageways are chosen to be grade separated, through their entire length or for part of it. Grade separation drastically increases the capacity of a road compared to an identical road with at-grade junctions. For instance, it is extremely uncommon to find an at-grade junction on a British motorway; it is all but impossible on a U.S. Interstate Highway, though a few do exist. If traffic can traverse the junction from any direction without being forced to come to a halt, then the junction is described as fully grade separated or free-flowing. Types Fully separated These junctions connect two freeways: Stack interchange (two-level, three-level, or four-level stack, depending on how many levels cross at the central point) Cloverleaf interchange Trumpet interchange Cloverstack interchange Directional T Semi-directional T Turbine (whirlpool) interchange Windmill interchange Various incarnations of spaghetti junction Partially separated These junctions connect two roads, but only one is fully grade-separated, i.e. traffic on one road does not have to stop at yield lines or signals on one road, but may have to do so when switching to the other: Diamond interchange Partial cloverleaf interchange Single-point urban interchange Roundabout interchange Compact grade-separation, whereby the two roads are linked by a compact "connector road", with major-minor priority junctions at each of its ends; usually a variant of the cloverleaf type interchange, but only involving two quadrants rather than four Weaving On roadways with grade-separated interchanges, weaving is a result of placing an exit ramp a short distance after an entry ramp, causing conflicts between traffic attempting to leave the roadway at the next junction and traffic attempting to enter from the previous junction. This situation is most prevalent either where the junction designer has placed the on-slip to the road before the off-slip at a junction (for example, the cloverleaf interchange), or in urban areas with many close-spaced junctions. The ring road of Coventry, England, is a notorious example, as are parts of the southern M25, the London orbital motorway, the M6/M5 junction north-west of Birmingham, and the A4/M5 junction west