Lane diet

Overview

Where a road diet removes a whole lane, a lane diet keeps the same lane count but makes each lane narrower, typically down to 10 or 10.5 feet from a wider original width. This is a lighter-touch alternative, useful where traffic volume doesn't support removing a lane but the existing lanes are wider than necessary for safe operation.

Where this leads: Target patterns

Default (Standard Collector) (COL-DEF-01), Default (No Parking, No Direct Access) (ART-DEF-01)

Applicability and thresholds

Appropriate on corridors where lane count must stay the same, due to volume or a jurisdiction's unwillingness to remove a lane, but where existing lanes exceed the width actually needed for safe operation at the corridor's design speed.

Evidence and effectiveness

A Canadian Institute of Transportation study presented in 2015 found side-impact and turn-related crash rates lowest where average lane widths fall between 10 and 10.5 feet, challenging the assumption that wider lanes are inherently safer.¹

Getting it built

Can move through the construction spectrum easily, since restriping to a narrower lane width is typically a paint-only change, well suited to a demonstration or pilot stage before permanent striping. See Construction Methodology & The Build Spectrum.

No formal decision process is typically required, since lane count is unchanged.

Who can move this

Usually a city or county public works decision, achievable through routine restriping without new legislation. See Legal & Planning Mechanisms.

Related retrofit strategies

Four-to-three lane road diet (RFT-CDR-01) (the more aggressive alternative where lane count itself can be reduced)

References

1. Evidence-based Findings presented at the Canadian Institute of Transportation Engineers annual meeting, June 2015, on lane width and side-impact/turn-related crash rates, as referenced in "Technical Guidance on Road Diets."