Right-in/right-out (RIRO) and left-in/left-out (LILO) refer to a type of three-way road intersection where turning movements of vehicles are restricted. A RIRO permits only right turns and a LILO permits only left turns. "Right-in" and "left-in" refer to turns from a main road into an intersection (or a driveway or parcel); "right-out" and "left-out" refer to turns from an intersection (or a driveway or parcel) to a main road. [1] [2] [3] RIRO is typical when vehicles drive on the right, and LILO is usual where vehicles drive on the left. This is because minor roads usually connect to the outsides of two-way roads. However, on a divided highway, both RIRO and LILO intersections can occur.
The remainder of this article refers only to RIRO but applies equally to LILO.
A RIRO intersection differs from a 3/4 intersection (right in/right out/left in) and an unrestricted intersection.
RIRO is an important tool of access management, itself an important component of transportation planning. A study applying access management guidelines to the redesign of Missouri Route 763 in Columbia, Missouri [4] illustrates how RIRO, combined with signalized intersections designed to permit U-turns, can accommodate high volumes of traffic with low delay and high safety.
The RIRO restriction typically is enforced through physical barriers such as a traffic island in an intersection to direct vehicles into the permitted turn, and to restrict vehicles from traveling through the intersection. The major road itself often has a median separating the two directions of traffic. The restriction may also be achieved by signage, but when a median or other barrier is not present in the median of the major road, RIRO configurations have been found to result in significant violation rates.[ citation needed ]
RIRO roads may also have grade-separated interchanges, but vehicles on these roads do not yield the right-of-way to other vehicles entering the roadway, nor encounter cross traffic. Such roads are sometimes called RIRO expressways. In the United States, they are sometimes called Jersey freeways, due to their prevalence in the state of New Jersey, although they are not limited to that state.
RIRO road configurations are an important tool for access management. General types of RIRO road configuration include limited access roads (e.g. divided highways) and roundabouts. To travel in the restricted direction, vehicles must first turn in the permitted direction, then reverse direction in a U-turn, by going around a roundabout, reversing direction at an interchange with an overpass or underpass, or by going left around a block. RIRO is especially useful where left turns would require crossing in front of oncoming vehicles.
RIRO configurations generally improve road-traffic safety and efficiency by reducing the number of conflict points between vehicles.
A RIRO configuration may improve safety and operations at one intersection while consequently worsening them at another intersection upstream or downstream.[ citation needed ]
Traffic comprises pedestrians, vehicles, ridden or herded animals, trains, and other conveyances that use public ways (roads/sidewalks) for travel and transportation.
An intersection or an at-grade junction is a junction where two or more roads converge, diverge, meet or cross at the same height, as opposed to an interchange, which uses bridges or tunnels to separate different roads. Major intersections are often delineated by gores and may be classified by road segments, traffic controls and lane design.
A three-way junction is a type of road intersection with three arms. A Y junction generally has three arms of equal size coming at an acute or obtuse angle to each other; while a T junction also has three arms, but one of the arms is generally a smaller road joining a larger road at right angle.
U.S. Route 46 (US 46) is an east–west U.S. Highway completely within the state of New Jersey, and runs for 75.34 mi (121.25 km). The west end is at an interchange with Interstate 80 (I-80) and Route 94 in Columbia, Warren County, on the Delaware River. The east end is in the middle of the George Washington Bridge over the Hudson River in Fort Lee, Bergen County, while the route is concurrent with I-95 and US 1-9. Throughout much of its length, US 46 is closely paralleled by I-80. US 46 is a major local and suburban route, with some sections built to or near freeway standards and many other sections arterials with jughandles. The route runs through several communities in the northern part of New Jersey, including Hackettstown, Netcong, Dover, Parsippany–Troy Hills, Wayne, Clifton, Ridgefield Park, Palisades Park, and Fort Lee. It crosses over the Upper Passaic River at several points. The road has been ceremonially named the United Spanish–American War Veterans Memorial Highway.
A Michigan left or P-turn is an at-grade intersection design that replaces each left (farside) turn at an intersection between a (major) divided roadway and a secondary (minor) roadway with the combination of a right (nearside) turn followed by a U-turn, or a U-turn followed by a right (nearside) turn, depending on the situation. It is in use in numerous countries.
A dual carriageway (BrE) or a divided highway (AmE) is a class of highway with carriageways for traffic travelling in opposite directions separated by a central reservation (BrE) or median (AmE). Roads with two or more carriageways which are designed to higher standards with controlled access are generally classed as motorways, freeways, etc., rather than dual carriageways.
In road transport, a lane is part of a roadway that is designated to be used by a single line of vehicles to control and guide drivers and reduce traffic conflicts. Most public roads (highways) have at least two lanes, one for traffic in each direction, separated by lane markings. On multilane roadways and busier two-lane roads, lanes are designated with road surface markings. Major highways often have two multi-lane roadways separated by a median.
A U-turn in driving refers to performing a 180° rotation to reverse the direction of travel. It is called a "U-turn" because the maneuver looks like the letter U. In some areas, the maneuver is illegal, while in others, it is treated as a more ordinary turn, merely extended. In still other areas, lanes are occasionally marked "U-turn permitted" or even "U-turn only."
A jughandle is a type of ramp or slip road that changes the way traffic turns left at an at-grade intersection. Instead of a standard left turn being made from the left lane, left-turning traffic uses a ramp on the right side of the road. In a standard forward jughandle or near-side jughandle, the ramp leaves before the intersection, and left-turning traffic turns left off of it rather than the through road; right turns are also made using the jughandle. In a reverse jughandle or far-side jughandle, the ramp leaves after the intersection, and left-turning traffic loops around to the right and merges with the crossroad before the intersection.
A limited-access road, known by various terms worldwide, including limited-access highway, dual-carriageway, expressway, and partial controlled-access highway, is a highway or arterial road for high-speed traffic which has many or most characteristics of a controlled-access highway, including limited or no access to adjacent property, some degree of separation of opposing traffic flow, use of grade separated interchanges to some extent, prohibition of slow modes of transport, such as bicycles, horse-drawn vehicles or ridden horses, or self-propelled agricultural machines; and very few or no intersecting cross-streets or level crossings. The degree of isolation from local traffic allowed varies between countries and regions. The precise definition of these terms varies by jurisdiction.
A superstreet is a type of road intersection that is a variation of the Michigan left. In this configuration, in contrast to the Michigan left, traffic on the minor road is not permitted to proceed straight across the major road or highway. Drivers on the minor road wishing to turn left or go straight must turn right onto the major road, then, a short distance away, queue (wait) into a designated U-turn lane in the median. When traffic clears, they complete the U-turn and then either go straight or make a right turn when they intersect the other half of the minor road.
A continuous flow intersection (CFI), also called a crossover displaced left-turn, is an alternative design for an at-grade road junction. Vehicles attempting to turn across the opposing direction of traffic cross before they enter the intersection. No left turn signal in the intersection is then necessary. Instead, vehicles traveling in both directions can proceed, including through vehicles and those turning right or left, when a generic traffic signal/stop sign permits.
A junction is where two or more roads meet.
Turn on red is a principle of law permitting vehicles at a traffic light showing a red signal to turn into the direction of traffic nearer to them when the way is clear, without having to wait for a green signal.
In the field of road transport, a turnaround is a type of junction that allows traffic traveling in one direction on a road to efficiently make a U-turn typically without backing up or making dangerous maneuvers in the middle of the traffic stream. While many junction types permit U-turns, the term turnaround often applies to road junctions built specifically for this purpose.
In traffic engineering, there are regional and national variations in traffic light operation. This may be in the standard traffic light sequence or by the use of special signals.
Access management, also known as access control, when used in the context of traffic and traffic engineering, generally refers to the regulation of interchanges, intersections, driveways and median openings to a roadway. Its objectives are to enable access to land uses while maintaining roadway safety and mobility through controlling access location, design, spacing and operation. This is particularly important for major roadways intended to provide efficient service to through-traffic movements.
A single carriageway is a road with one, two or more lanes arranged within a one carriageway with no central reservation/median strip to separate opposing flows of traffic. A single-track road is a type of single carriageway with a single lane with passing places for traffic in both directions. An undivided highway is the term used for motorways with two or more lanes with no central reservation/median strip. Road traffic safety is generally worse for high-speed single carriageways than for dual carriageways due to the lack of separation between traffic moving in opposing directions.
A seagull intersection or continuous green T-intersection is a type of three-way road intersection, usually used on high traffic volume roads and dual carriageways. This form of intersection is popular in Australia and New Zealand, and sometimes used in the United States and other countries.
Terminology related to road transport—the transport of passengers or goods on paved routes between places—is diverse, with variation between dialects of English. There may also be regional differences within a single country, and some terms differ based on the side of the road traffic drives on. This glossary is an alphabetical listing of road transport terms.