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Highway lane-width standards, when applied in cities, result in overly wide, undifferentiated lanes that perform poorly at most times of the day, with speeding at off peak times and lane-splitting during peak traffic periods. Reducing lane width to 3 m or less promotes safe driving speeds in an urban environment.
Wide travel lanes have been favored in some places to create a more forgiving environment for drivers, especially in high-speed environments where narrow lanes may feel uncomfortable or increase potential for side-swipe collisions. Lane widths of less than 3.5 m have been assumed to decrease traffic flow and capacity, a claim that new research refutes.1
Lane widths of 3 m are appropriate in urban areas and have a positive impact on street safety without impacting traffic operations. For designated truck or transit routes, one travel lane of 3.3 m may be used in each direction. In select cases, narrower travel lanes of 2.7–3 m can be effective as through lanes in conjunction with a turn lane.2 Lanes greater than 3 m are discouraged as they enable unintended speeding and double parking, and consume valuable right-ofway at the expense of other modes.
Restrictive policies that favor the use of wide travel lanes have no place in constrained urban settings, where every centimeter counts. Research has shown that narrower lane widths can effectively manage speeds without decreasing safety, and that wider lanes do not correlate to safer streets.3 Moreover, wider travel lanes increase exposure and crossing distance for pedestrians.4 Lane width should be considered within the overall assemblage of the street.
In multi-lane roadways where transit or freight vehicles are present, one wider travel lane may be provided. The wider lane should be the outside lane, curbside or next to parking. Inside lanes should continue to be designed at the minimum possible width at 3 m or less.
Parking lane widths of 1.8–2.5 m are recommended. Cities are encouraged to demarcate the parking lane to indicate to drivers how close they are to parked cars.
1. Theo Petrisch, “The Truth about Lane Widths,” The Pedestrian and Bicycle Information Center, accessed June 6, 2016, http://www.pedbikeinfo.org/data/library/details.cfm?id=4348
2. Research suggests that lane widths of less than 12 feet on urban and suburban arterials do not increase crash frequencies.
Ingrid Potts, Douglas W. Harwood, and Karen R. Richard, “Relationship of Lane Width to Safety on Urban and Suburban Arterials,” (paper presented at the TRB 86th Annual Meeting, Washington, DC, January 21–25, 2007): 1–6.
3. Eric Dumbaugh and Wenhao Li, “Designing for the Safety of Pedestrians, Cyclists, and Motorists in Urban Environments.” Journal of the American Planning Association 77 (2011): 70.
4. Previous research has shown various estimates of relationship between lane width and travel speed. One account estimated that each additional foot (0.3 m) of lane width related to a 2.9 mph (4.7 km/h) increase in driver speed.
Kay Fitzpatrick, Paul Carlson, Marcus Brewer, and Mark Wooldridge, “Design Factors That Affect Driver Speed on Suburban Arterials,” Transportation Research Record: Journal of the Transportation Research Board 1751 (2000):18–25.
Adapted by Global Street Design Guide published by Island Press.