Retrofits · Corridor
RFT-CDR-02Five-plus lane reallocation
Reduces the through-lane count on a roadway of five or more lanes, applying road diet principles at a larger scale than the standard four-to-three conversion.
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#Overview
Wider roadways, five lanes and up, carry enough volume and turning complexity that a straightforward four-to-three conversion doesn't apply directly. This strategy still removes excess through capacity and adds or widens a center turn lane, but requires more careful traffic analysis and often a phased approach, since five-lane-and-larger corridors typically carry higher volumes and more conflicting turning movements than the classic road diet case.
Related Media
5 items
Aligned(opens in new tab)The Dutch Solution for Safer Sidewalks - Continuous Sidewalks
Not Just BikesShows the same sidewalk-continuity concept behind Continuous Sidewalk / Raised Junction in practice: the roadway rises to meet the sidewalk at a crossing, rather than the sidewalk dropping to meet the road, so geometry itself signals the priority shift.
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Aligned(opens in new tab)What Happens If You Remove a Highway?
StreetcraftThe video looks at cities that removed urban highways, from Rochester's Inner Loop to Seattle's Alaskan Way Viaduct, and what replaced them. It is a real-world case for the Commonway System's road diet and corridor reallocation strategies.
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Aligned(opens in new tab)Rochester gave up on a highway and filled it in. Should Baltimore?
The Baltimore BannerThis long-form report traces Rochester's Inner Loop East removal, which turned a sunken expressway trench into homes, a bike path, and a boulevard. It is a deep single-city case for the Commonway System's highway-removal reasoning and corridor reallocation strategies.
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Aligned(opens in new tab)How Money for Highways Could Have Built 36 Paris Metros (Ep 590)
Talking HeadwaysThe episode covers a data project mapping the tax base and land value that urban freeways stripped from 142 American cities. It documents the costs behind the Commonway System's skepticism of urban highway building.
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Aligned(opens in new tab)America's deadliest road, explained
VoxVox examines a one-kilometer stretch of US-19 in Florida, the deadliest of 60 pedestrian-fatality hotspots in a national study, and shows how eight lanes, 45 mph speeds and crossings nearly a kilometer apart make deaths predictable rather than accidental. It is a vivid case study of the Stroad problem and of the crosswalk, signal, driveway and lane-removal fixes the Commonway System specifies.
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#Where this leads: Target patterns
- Default (No Parking, No Direct Access) (ART-DEF-01)
- Boulevard (ART-BLV-02)
#Applicability and thresholds
Evaluated specifically for roadways with five or more lanes in NCHRP-adjacent research, distinct from the four-to-three case. Sight-distance and conflict-point improvements follow the same underlying mechanism as a standard road diet, but volume thresholds run higher given the additional capacity these corridors typically carry.
#Evidence and effectiveness
Research on five-lane-and-larger road diet projects documents conflict-point reduction and improved sight distance for turning drivers, using the same two-stage reasoning as smaller road diets: fewer lanes to scan, and a dedicated turn lane separating through and turning movements.1
#Getting it built
Can move through the construction spectrum, though the larger scope, more lanes, more signal coordination, more turning-movement analysis, makes a formal pilot or quick-build stage more valuable here than on a simple four-to-three conversion. See Construction Methodology & The Build Spectrum.
An Intersection Control Evaluation is worth considering where the corridor's intersections will also see a change in turn-lane configuration. See Decision & Evaluation Processes.
#Who can move this
Typically a city or county transportation department decision, though the larger scope and often-higher-classification roadway makes state DOT coordination more likely than with a simple four-to-three road diet. See Legal & Planning Mechanisms.
#Related retrofit strategies
- Four-to-three lane road diet (RFT-CDR-01) (the smaller-scale equivalent this strategy extends)
#References
- Evidence-based "An Evaluation of 'Road Diet' Projects on Five Lane and Larger Roadways," transportation research summary distributed via NACTO.(opens in new tab)
- Legal / regulatory Federal Highway Administration, "Road Diets (Roadway Reconfiguration)," Proven Safety Countermeasures, FHWA-SA-12-013.(opens in new tab)