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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.

Related Media

The items below come from outside the Commonway System, external videos, podcasts, and articles related to this page's topic, not part of the guidebook itself.

Aligned

The Dutch Solution for Safer Sidewalks - Continuous Sidewalks

Not Just Bikes

Shows 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.

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.