Planners and Architects

Narrow or Reduce Travel Lanes

Streets frequently have more space allotted to cars than is necessary. This tactic entails redesigning new or existing roadways to reduce the width and number of travel lanes wherever possible. Techniques for achieving this include “road diets” and reducing travel-lane widths. A “road diet” typically refers to converting a roadway with two lanes in each direction to one lane in each direction with a center turning lane and bike lanes on the side.

Guidance
  • Travel-lane widths should not be based on the widest width allowable, but on the narrowest safe width
  • Evaluate transit routes, the number and design of intersections along the corridor, the number of driveways, and operational characteristics before implementing a road diet
  • Consider designing local streets that are too narrow for two full lanes to accommodate alternating two-way traffic
  • Analyze and understand the effects of the proposed change, and obtain input from the community stakeholders
  • Include contextual safety improvements in the project, such as intersection turn lanes, signing, pavement markings, signals or stop signs, transit stops, medians, sidewalk improvements, and bike lanes
Benefits
  • Provides more roadway width for sidewalks and bicycle lanes
  • Often shortens crossing distances for pedestrians
  • Creates more space for medians, bike lanes, on-street parking, transit stops, and landscaping
  • Improves pedestrian and cyclist safety
  • Makes more efficient use of underused pavement
  • May slow vehicular speeds
Considerations
  • Be cautious of 9’–10’ travel lanes in the following contexts:
    • Four-lane arterial roads
    • Four-leg stop-controlled arterial intersections
    • High-speed roadways with narrow shoulders
    • High-speed curvy roadways
    • Locations with high volumes of buses and/or truck
Where to Use It
  • Roadways with average daily traffic (ADT) of 20,000 vehicles or less may be good candidates for a road diet
  • The American Association of State and Highway Transportation Officials recommends the following minimum travel lane widths by context
    • Freeways: 12’
    • Urban and suburban arterials: 10’
    • Rural arterials: 11’
    • Collector roadways: 10’
    • Local roads: 9’
    • Reduced-speed urban areas (45 mph and under): 10’
    • Urban and suburban commercial centers: 9’
    • Urban and suburban commercial neighborhoods: 9’–11’
Professional Consensus
  • AASHTO permits lane-width minimums of 10′ on urban arterial and collector roadways with posted speed limits of 45 mph or less and 9’ lane-width minimums on local roads
  • Endorsed by Federal Highway Administration
  • Endorsed by PennDOT/NJDOT’s Smart Transportation Guidebook, which encourages designers to “make full use of the normal range of travel lane widths….depending on context and project goals.”
Examples

Many cities stripe 10’ lanes on urban arterials, including:

This material is the product of a partnership between America Walks and Sam Schwartz Engineering. Visit here for more information on the partnership.