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,