Commonway
Version V. 2026.09.03

Five-plus lane reallocation

RFT-CDR-02 Corridor

Five-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.

#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.

#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.

Four-to-three lane road diet (RFT-CDR-01) (the smaller-scale equivalent this strategy extends)

#References

  1. Evidence-based "An Evaluation of 'Road Diet' Projects on Five Lane and Larger Roadways," transportation research summary distributed via NACTO.
  2. Legal / regulatory Federal Highway Administration, "Road Diets (Roadway Reconfiguration)," Proven Safety Countermeasures, FHWA-SA-12-013.

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