Reduce Lane Number:

Before (top) and after (bottom) road diet.

Illustration by A.J. Silva

Photo by Dan Burden
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Some roads have more travel lanes than necessary, and the width of the excess lanes could be freed up for other uses. Space may be better used for bicycle lanes, parking, or wider pedestrian buffers or sidewalks (with curb realignment). A traffic analysis should be done to determine whether the number of lanes on a roadway (many of which were built without such an analysis) is appropriate. Reducing the number of travel lanes may also slow travel speeds.

A typical "road diet" may involve converting an undivided four-lane roadway to one travel lane in each direction, with an ongoing center left-turn lane. Road diets have also replaced the second travel lanes with a raised median and turn pockets, and bike lanes in each direction. A raised median allows greater control of turning movements and may enhance bicyclist as well as motorist safety in some circumstances (see Medians/Crossing Islands).

A variety of reconfigurations are possible for lane number reductions depending on the current configuration, user needs, and potential operational and safety outcomes. Other measures could be implemented simultaneously to complete the overall redesign for the street.

Purpose

  • Remedy a situation where there is excess capacity.
  • Provide space for bicyclists, pedestrians, or parking.
  • Reduce apparent width of the road; provide median refuge.
  • Improve social interaction and enhance livability of the street.

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Considerations

  • Traffic studies should determine whether there is excess capacity.
  • Studies that include safety effects as well as traffic operations should help to determine preference for an on-going left turn option or whether intermittent left turns will provide the level of service needed.

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Estimated Cost

The cost for restriping a kilometer of four-lane street to one lane in each direction plus a two-way, left-turn lane and bike lanes is about $3,100 to $12,400 ($5,000 to $20,000 per mi), depending on the amount of lane lines that need to be repainted. The estimated cost of extending sidewalks or building a raised median is much higher and can cost $62,000 per km ($100,000 per mi) or more. If a reconfiguration is done after repaving or with an overlay, and curbs do not need to be changed, there is little or no cost for space reallocations accomplished through new striping.

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Case Studies

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