One-Way/Two-Way Street Conversions:

One-way streets can simplify crossings for pedestrians, who must look for traffic in only one direction. While studies have shown that conversion of two-way streets to one-way generally reduces pedestrian crashes, one-way streets tend to have higher speeds, which creates new problems. If a street is converted to one-way, it should be evaluated to see if additional changes should be made, especially if the street or lanes are overly wide. Also, traffic circulation in the surrounding area must be carefully considered before conversion to one-way streets.

As a system, one-way streets can increase travel distances of motorists and bicyclists and can create confusion, especially for non-local residents. One-way streets operate best in pairs, separated by no more than 0.4 km (0.25 mi). Conversion costs can be quite high to build cross-overs where the one-way streets convert back to two-way streets, and to rebuild traffic signals and revise striping, signing, and parking meters.

One-way streets work best in downtown or very heavily congested areas. One-way streets can offer improved signal timing and accommodate odd-spaced signals; however, signal timing for arterials that cross a one-way street pair is difficult.

Conversions can go the other way as well: some places are returning one-way streets back to two-way to allow better local access to businesses and homes and to slow traffic. Two-way streets tend to be slower due to “friction,” especially on residential streets without a marked center line, and they may also eliminate the potential for multiple-threat crashes that exists on multi-lane, one-way streets.



  Purpose
• Manage traffic patterns.
• Reduce conflicts.
• A one-way to two-way conversion will generally reduce speeds.
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  Considerations
• Consider impacts on other streets.
• Be aware that one-way streets may decrease automobile accessibility to businesses.
• Be careful not to create speeding problems where a two-way street is changed to a one-way street. Redesign or traffic-calming measures may be required to address this.
• Will improve signal synchronization on the one-way streets, but will hinder synchronization on cross-streets.
• Generally requires a one-way pair, with two nearby streets being converted to one-way.
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  Estimated Cost
$12,400 to $124,000 per kilometer ($20,000 to $200,000 per mile), depending on length of treatment and whether the conversion requires modification to signals. If crossovers are needed at the end points of the one-way streets, they may cost millions of dollars.
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  Case Studies
Allegheny County, PA 
Cambridge, MA 
Hendersonville, NC 
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U.S. Department of Transportation Federal Highway Administration