Editing Right-in/right-out

{{Short description|Type of road intersection}}
'''Right-in/right-out''' ('''RIRO''') and '''left-in/left-out''' ('''LILO''') refer to a type of [[three-way junction|three-way road intersection]] where turning movements of [[vehicle]]s 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 [[land lot|parcel]]); "right-out" and "left-out" refer to turns ''from'' an intersection (or a driveway or parcel) to a main road.<ref> {{cite web | url = http://www.udot.utah.gov/main/uconowner.gf?n=11066229893635233 | title = Title 930 (Transportation, Preconstruction), Rule R930-6 (Access Management) | work = Utah Administrative Code | publisher = [[Utah Department of Transportation]] | format = PDF | date = August 2013 | access-date = September 12, 2015 }} </ref><ref> {{cite web | url = http://www.rules.utah.gov/publicat/code/r930/r930-006.htm#T5 | title = Title 930 (Transportation, Preconstruction), Rule R930-6-5 (Access Management, Definitions) | work = Utah Administrative Code | publisher = Utah Department of Administrative Services, Division of Administrative Rules | date = August 1, 2015 | access-date = September 12, 2015 }} </ref><ref> {{cite web | url = http://www.dot.state.mn.us/accessmanagement/docs/pdf/manualchapters/chapter3.pdf | title = Access Management Manual, Chapter 3 (Guidelines for Public Street and Driveway Connections), 3.4.6 (Restricted Movements and Median Openings) | publisher = [[Minnesota Department of Transportation]] | format = PDF | date = January 2, 2008 | access-date = September 12, 2015 }} </ref> RIRO is typical when vehicles [[Left- and right-hand traffic|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 road]]s.  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.

[[File:Rotor Zagreb-crop.jpg|thumb|(Lower left) RIRO ramps on and off a divided highway connecting to the [[Remetinec Roundabout]] in [[Zagreb|Zagreb, Croatia]].]]
[[Image:2007 09 14 - MD355 @ NIH Visitor Access 2.JPG|thumb|right|A right-in/right-out intersection at the entrance to the [[National Institutes of Health]] along [[Maryland Route 355]] in [[Bethesda, Maryland]], [[United States]].]]
[[File:11 cl km 141-1 north lg.jpg|thumb|left|[[Ontario Highway 11|King's Highway 11]], looking north from overpass, toward South Sparrow Lake Road/Goldstein Road in [[Severn, Ontario]], [[Canada]].<br>Several characteristics of a ''RIRO expressway'' are shown in the image: there is an unbroken [[central reservation|median]], there are right-in/right-out turns at the side roads, there are businesses with direct right-in/right-out [[frontage]] along the highway, and there is a sign indicating that access to the southbound [[carriageway|lanes]] of the highway is via a right turn onto the side road (in this case, by following Goldstein Road to the overpass road, crossing over the highway, then continuing on the overpass road to South Sparrow Lake Road).]]
[[File:11 cl km 141-1 south lg.jpg|thumb|left|King's Highway 11, looking south from same overpass. In addition to the unbroken median, this image shows another characteristic of a ''RIRO expressway'': direct right-in/right-out access to driveways (in this case, residential).]]

==Design==
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]]<ref>{{cite journal
|title=Implementing MoDOT’s Access Management Guidelines Along Route 763 
|author=Kenny Voss and Trent Brooks and Tim Rogaczewski and Michael Trueblood
|year=2008
|pages=13
|journal=7th National Conference on Access Management
|publisher=Transportation Research Board, Access Management Committee AHB70
|url=http://www.accessmanagement.info/AM08/AM0805Trueblood/AM0805Trueblood.pdf
|access-date=2009-06-24
}}</ref> illustrates how RIRO, combined with signalized intersections  designed to permit [[U-turn]]s, 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 [[central reservation|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|date=June 2009}}

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 [[transportation in New Jersey#Right-in/right-out expressways|prevalence]] in the state of [[New Jersey]], although they are not limited to that state.

==Use==
RIRO road configurations are an important tool for [[access management]]. General types of RIRO road configuration include [[limited access road]]s (e.g. [[divided highway]]s) and [[roundabouts]]. To travel in the restricted direction, vehicles must first turn in the permitted direction, then reverse direction in a [[U-turn (maneuver)|U-turn]], by going around a [[roundabout]], reversing direction at an [[Interchange (road)|interchange]] with an [[overpass]] or [[underpass]], or by going left around a [[city block|block]]. RIRO is especially useful where left turns would require crossing in front of oncoming vehicles.

==Safety==
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|date=June 2009}}

==References==
{{reflist|2}}

== External links ==
{{commons category}}
* [https://web.archive.org/web/20090501233637/http://www.onthighways.com/riro.htm Introduction to RIRO Expressways, OntHighways.com]
* [http://www.asphaltplanet.ca/ON/index.html Ontario Highways, asphaltplanet.ca (former OntHighways.com)]

{{road types}}

{{DEFAULTSORT:Right-in right-out}}
[[Category:Transportation planning]]
[[Category:Road junction types]]
[[Category:Limited-access roads]]
[[Category:Controlled-access highways]]