Should cities convert one-way streets to two-way?

by Randal O'Toole The Thoreau Institute


The latest fad among urban planners is to convert one-way streets to
two way. The goal, they say, is to slow down traffic and make streets
more pedestrian friendly.

One-way to two-way conversions are being planned or implemented in
Austin, Berkeley, Cambridge, Chattanooga, Cincinnati, Louisville,
Palo Alto, Sacramento, San Jose, Seattle, St. Petersburg, and Tampa,
among other cities. These proposals have become a major source of
controversy in at least some of these cities, especially Austin,
Cincinnati, and Chattanooga.

By almost any measurable criteria -- safety, pollution, congestion,
and effects on most local businesses -- one-way streets are superior
to two way. The idea that two-way streets are superior because they
are more pedestrian friendly is just a planner's fantasy that
disguises their real intent: to create an auto-hostile environment.

The History of One-Way Streets

Most one-way streets in this country were first created from two-way
streets in the 1930s through the 1950s. These conversions took place
in areas built before the automobile became the prevalent form of
transportation. Such areas tend to have narrower streets and smaller
blocks than post-auto cities. One-way streets were thus an attempt to
accommodate auto traffic in areas not built for the auto. The wider
streets and longer blocks typical of post-auto areas often allow
improved traffic flows without one-way streets.

Before the 1990s, transportation policy was firmly in the hands of
traffic engineers, whose primary goal was safety and secondary goal
was the movement of people and goods. Cities that converted two-way
to one-way noted a significant decline in accidents.

One-way streets have the obvious advantage that pedestrians and
drivers need only look one way when watching for traffic. How many
times have you looked both ways when crossing a two-way street, only
to be nearly hit by a car coming from the direction in which you
weren't looking at the moment you entered the intersection?

One-way streets also permitted higher average speeds because signals
on a one-way grid could be synchronized to allow drivers in all
directions to proceed indefinitely at a fixed rate of speed. A
semblance of synchronization can be approached on a two-way grid only
if signals are more than a half-mile apart, and even then it is less
than perfect. Traffic on two-way streets, for example, is often
delayed by special left-turn signals, which aren't needed on one-way

Faster speeds on signal-synchronized one-way streets increased road
capacities without laying more pavement. Since the increase was in
the average rate of speed, not the top speed, increased speeds posed
no loss in safety. One way streets not only have greater capacity
than two-way streets, they save the space that two-way streets
require for left-turn lanes.

In the 1970s, a new goal -- reduced air pollution -- led to more
conversions of two-way streets to one way. The smooth flow of traffic
allowed by signal synchronization meant less auto emissions. Since
cars pollute more at slower speeds and in stop-and-go traffic,
one-way streets can generate significantly less pollution than

Proposals to Convert Back to Two Way

Today, transportation policy is in the hands of urban planners who
claim their goal is to make cities more livable by designing them for
people, not cars. The fact that people in most American cities do 85
to 95 percent of their travel by car does not deter planners from
making this artificial dichotomy.

"A pedestrian-oriented hierarchy of transportation promotes density,
safety, economic viability, and sustainability," says Austin's
Downtown Design Guidelines. In transportation planning, "sustainable"
has become a code word for "anything but automobiles." Beyond this,
Austin does not say why density is an appropriate goal, nor have
planners shown how a pedestrian orientation is more economically
viable than an auto orientation.

Austin goes on to say, "The safety and comfort of pedestrians is of
greater concern than the convenience of a driver." This statement
assumes that pedestrian safety and comfort is incompatible with the
convenience of drivers. In fact, there is no reason why this must be

Planners only sometimes admit that their real goal is to discourage
driving by creating auto-hostile environments. Since every single car
on the road has at least one person in it who is trying to get
somewhere, this is hardly a people-friendly attitude. More important,
in their single-minded opposition to the auto, planners have
forgotten about safety, environmental, and social concerns.

Two Kinds of One-Way Streets

The controversy over converting streets back to two way involves two
different kinds of one-way streets. First is the downtown grid, which
typically has traffic signals at every intersection that are set for
speeds of 15 to 20 miles per hour. Second is the one-way couplet, two
streets that feed traffic into downtowns or other busy areas. These
typically have traffic signals only at major intersections which, if
they are synchronized, are typically set for speeds of 25 to 40 miles
per hour.

Conversion of part of a downtown grid to two way means a significant
loss of both safety and traffic flow. Other than the psychic benefit
some people get when they see other people stuck in traffic, such
conversions have no positive results. In fact, they are likely to
contribute to downtown decay as they reduce the capacity of streets
to carry traffic into and through downtowns.

Converting one-way couplets to two way could reduce flow capacities
by nearly half. "You need seven lanes of a two-way arterial to
achieve the same capacity as four lanes of a one-way couplet," says
transportation planning Michael Cunneen. However, planners usually
want to reduce traffic flows by even more than this amount. Their
proposals often call for:
* Reducing the number of lanes of auto traffic;
* Narrowing lane widths;
* Removing right- and/or left-turn lanes;
* Adding median strips or other barriers to streets: and
* Other traffic-calming (i.e., congestion-building) actions.

In Chattanooga, for example, McCallie and ML King avenues form a
one-way couplet of four broad lanes in each direction. The city plans
to convert both to two way. ML King would have two lanes in each
direction, but McCallie would be reduced to one lane in each
direction plus an intermittent left-turn lane. The two lost lanes
would be turned to on-street parking. The result would be a net loss
of two lanes, and the remaining lanes would be slower (meaning lower
in capacity) than the current lanes.

Planners say these steps will make streets more pedestrian friendly
and that the resulting reduction in speeds will make up for the
reduced safety of two-way streets. However, planners' real goal is to
reduce roadway capacities.

Planners in Chattanooga and certain other cities, such as St.
Petersburg, argue that the decline of downtown areas since streets
were converted to one way has reduced the need for roadway capacity,
so the reduction in capacity is not a problem. However, limited
capacity would inhibit the downtown revitalization that planners say
is also their goal.

Economic Vitality

Planners assert, with little or no evidence, that two-way streets
will revitalize downtowns and other areas. One-way streets supposedly
hurt businesses by forcing some people to drive around a block to get
to those businesses. Yet the higher average speeds of one-way streets
(due to signal synchronization) reduces the total time it takes
people to get to any destination even if they sometimes have to drive
around a block.

Planners also argue that one-way streets have higher top speeds than
two-way streets, and that a lower top speed makes it more likely that
drivers will see and stop at businesses along the way. But the top
speed of a street is independent of whether it is one way or two way.
What planners mean is that when they convert to two way they also
plan to reduce top speeds.

"One-way streets are a 1970s traffic engineer's approach to getting
traffic out of downtown," says Donald A. Shea, who represents a
downtown St. Petersburg advocacy group. "Well, it worked. And some of
it has never come back."

Shea is confused. One-way streets allow more traffic into as well as
out of downtown. Businesses that left downtowns for the suburbs did
so in part because downtowns were more congested than the suburbs. To
the extent that one-way streets reduced congestion, they mitigated,
rather than contributed to, downtown decline. Of course, downtowns
declined for many reasons other than congestion, but there is no
reason to suspect that converting one-way to two-way streets will
reverse this decline.

This does not mean that no businesses would benefit from a conversion
to two-way streets. Certainly many businesses complained that
converting two-way to one-way in the 1950s led to a loss in revenues.
The truth is that some businesses probably do better on a two-way
street while others thrive on a one-way couplet.

Supermarkets and other high-volume, low-margin stores that have their
own parking lots (most of which are dominated by one-way lanes)
probably do better on a one-way couplet that gives lots of people
quick access to those stores. Specialty stores that rely on impulse
sales and depend on high margins per sale might do better on two-way
streets, since only half their potential customers would see them on
a one-way couplet.

Some people argue that such considerations are purely private and not
the business of government. "The primary purpose of roads is to move
traffic safely and efficiently, not to encourage or discourage
business or build or rebuild parts of town," argues engineering
Professor Joseph Dumas, of the University of Tennessee at
Chattanooga. "Streets are tools for traffic engineering, not social

Dumas might say that a business that does best on a two-way street
should locate on a two-way street. Many planners, of course, would
disagree and claim that it is the business of government to promote
business. However, there is no evidence that two-way streets and
reduced traffic flows will do so.

Past efforts to promote pedestrian-oriented downtowns often involved
complete exclusion of automobiles from certain streets. Such
pedestrian malls have occasionally been successful, such as Pearl
Street in Boulder. But more often they have led to the death of
businesses on the mall.

Eugene, Oregon, turned three major downtown streets into a pedestrian
mall in 1971. Local businesses noted an immediate drop in sales, and
Sears, Penneys, Wards, and other stores soon pulled out. Yet it took
two decades for city planners to give up and re-open the streets to
auto traffic. One street was opened in 1992, another in 1996.

In 2001, two out of three Eugene voters supported a plan to open up
the last street of the pedestrian mall to autos. Downtown business
leaders called this "the critical first step in revitalizing"

Turning one-way streets to two way and other congestion-building
measures are not as auto hostile as completely closing streets to
autos -- but they have the same anti-auto aim. There is no reason to
think that reducing roadway capacities will revitalize downtowns any
better than eliminating roadway capacities.


The evidence that two-way streets are more dangerous than one way is
overwhelming. In many cases, two-way streets result in twice as many
pedestrian accidents as one way.

One review of two-way to one-way conversions found that two-way
streets caused 163 percent more pedestrian accidents in Sacramento,
and 100 percent more pedestrian accidents in Portland OR, Hollywood
FL, and Raleigh NC. This study called one-way streets "the most
effective urban counter-measure" to pedestrian accidents.

One-way streets also lead to fewer motor vehicle collisions. While
the reduction in collisions is not as great as the reduction in
pedestrian accidents, Michael Cunneen says, "two-way streets are
designed more for auto body shops than for people or cars."

Since most conversions of two-way to one-way streets were done in the
1950s, few studies are available on the internet. The above-cited
study is from 1976, and is titled "National Highway Safety Needs
Study," published by the Research Triangle Institute for the US
Department of Transportation.

The claim that slowing traffic will reduce the safety problems of
two-way streets is diminished by the fact that congested streets with
narrow lanes will also slow emergency service vehicles. As pointed
out in "The Vanishing Automobile," studies of traffic calming show
that delays to emergency service vehicles will kill far more people
than will be saved by the slower speeds (p. 352).


Cars pollute more at lower speeds than at higher speeds. They also
pollute more when they accelerate than when they travel at a constant
speed. Thus, the stop-and-go traffic that is more likely on two-way
streets than one way, as well as the slowdowns planners seek by
narrowing lanes, both lead to increased air pollution.

In fact, when Congress first required cities to reduce air pollution
in the 1970s, many cities responded by improving signal
synchronization and speeding up traffic downtown. Faster speeds meant
less congestion and lower emissions. Since downtowns were the
location of the most concentrated pollutants, such lower emissions
could make the difference between pollution violations and compliance
with federal pollution laws. Even today, signal synchronization is
the most cost-effective thing most cities can do to improve air

Most planners today ignore this side-effect of their pedestrian
fantasies. But planners in Austin took the trouble to calculate that
converting several one-way streets to two way would increase traffic
delays by 23 percent and increase downtown air pollution by 10 to 13
percent. That's a huge increase in pollution for a policy with such
questionable benefits -- especially since air pollution is the main
legal justification planners have for trying to reduce the amount of
driving we do.


Increased auto ownership and driving is largely a function of income.
As incomes rise, more people buy cars. Auto ownership gives
low-income people access to more jobs, especially considering that
commuter auto speeds remain more than double commuter transit speeds.
Autos also provide better access to low-cost consumer goods and

Low-income people tend to remain concentrated in the inner cities
where planners most often propose to convert one-way to two-way
streets. The loss of mobility imposed by these conversions will fall
most heavily on such low-income people. Higher income people are more
likely to live and work in the post-auto suburbs where one-way
streets are rare because they weren't needed to accommodate auto

Gainesville, Florida, is considering a plan to reduce its major
east-west thoroughfare from four lanes to two lanes. Since most of
the city's low-income people live on the east side and most of the
jobs are on the west side, this action will severely reduce
low-income access to jobs. Proposals to reduce speeds when converting
one-way to two-way streets in other cities will similarly harm
low-income people.


Converting one-way to two-way streets is "a huge waste of money,"
says Fabian Bandoni, Cambridge's former director of engineering. St.
Petersburg, for example, estimates that it will cost nearly $150,000
to convert each major intersection that is changed from one way to
two way. Converting an entire one-way couplet or a portion of a
downtown grid may run into the tens of millions of dollars.

The debate over one way to two way has led many traffic engineers to
publicly object to these plans. In Cambridge, Chattanooga, and other
cities, traffic engineers have become outspoken opponents of one-way
to two-way conversions.

Planners probably consider traffic engineering goals of safety,
traffic flows, and reduction in pollution to be archaic. But the cost
issue may sway many city councils, especially considering the current


On just about any ground imaginable -- safety, congestion, pollution,
and effects on most businesses -- one-way grids and one-way couplets
are a superior method of moving people and vehicles. The idea that
pedestrian-friendly design can be enhanced by creating more
pedestrian-deadly environments is just a planning fantasy.

Randal O'Toole The Thoreau Institute

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