By Dom Nozzi
Creating one-way streets was popular a number of decades ago as an low-cost way to quickly move high volumes of traffic through downtown. Perceived benefits included:
Improved Traffic Flow. One-way streets, by removing on-coming traffic, reduce the “friction” that motorists experience on a street. This tends to reduce motorist delays and increase motorist speeds because the perception of risk is reduced. The street is perceived to feel more like a raceway, and drivers tend to drive at the highest possible speed at which they feel safe. On a “raceway,” that “safe speed” can be quite high.
Lower Cost. Compared to road widening, conversion of a two-way street to one-way operation is a comparatively cost-free means of increasing traffic volumes and speeds on a street. (However, research has shown that the highest volumes are carried on streets that have speeds of no more than 30 mph, where the distance between motor vehicles is quite modest.) Changing regulatory signs and street markings is much less costly than acquiring right-of-way, removing structures, and constructing new roadway as a way to increase street capacity. Fewer traffic lanes are needed to carry the same volume of motor vehicles with one-way streets. This can create more space for on-street parking or in-street bicycle lanes without increasing street pavement width. Wider sidewalks might also be possible without additional right-of-way. In addition, on one-way streets, traffic signal operation is simplified.
Reduced Conflicts. One-way streets eliminate left-turn conflicts by motorists, which can reduce crashes.
Increased Affordable Housing. Because one-way streets are hostile to residential neighborhoods, as noted below, they tend to increase the supply of affordable housing in a community.
However, there are a large number of problems with one-way streets that tend to overwhelm the above benefits.
Problems Associated with One-Way Streets
Nationally, cities are converting one-way streets back to two-way because of the many problems that one-ways create. For example, Ecologically Sustainable Design Pty Ltd (2005) reports that “[m]any of these town centres [in the United States] became quite degraded, unattractive and unsafe into the 1980s and 1990s, in part as a result of the impact of car-based sprawl development beyond the town centres, but also because of the effects of traffic dominance on the one-way streets.”
Increase in Average Vehicle Speed. One-way streets result in a significant increase in speeding. Former “shopping streets” (often including residences) become increasingly abandoned drive-throughs instead of drive-tos. By increasing average motor vehicle speeds, one-way streets tend to induce lower-value car trips that were previously discouraged by slower-speed travel. This induced travel increases per capita motor vehicle travel, which increases air and noise pollution, and gas consumption, thereby aggravating global warming.
Increase in Motorist Inattentiveness. Because one-way streets remove on-coming traffic, “friction” is reduced and the motorist therefore has less of an obligation to pay attention while driving. Without the “risk” of an on-coming car, the potential cost of straying from the travel lane is reduced, which leads some motorists to engage in multi-tasking behavior such as talking on a cell phone or taking his or her eyes off of the road to find something inside the car.
Harm to Retail and Residential Neighborhoods. Long-standing one-way streets seem to lose residences and businesses due to the more hostile, noisier, higher speed conditions. For a residence, in addition to the perceived increase in danger and noise pollution, the higher speeds create the impression of excessive traffic volumes, even if volumes are modest. Businesses are harmed, in part, due to the lower storefront exposure the business now experiences on the one-way street, as one direction of travel (and the exposure of the lost direction) is eliminated. Storefront exposure is also reduced by the increased speed of motor vehicles, whereby the motorist has less time to “read” a storefront or sign. In addition, businesses are also harmed because delivery trucks can be inconvenienced.
As of January 2000, Ecologically Sustainable Design Pty Ltd (2005) reports that “22 cities across the USA that have converted one way streets back to two-way. …[the] vast majority reported the conversion was very positive, particularly for business development.”
The loss in residential quality and commercial value causes a decline in property values. As the resulting abandonment of property goes up, signs of decline such as drug activity or prostitution tend to increase. These behaviors tend to go up in a more abandoned “no man’s land” created by the above-cited impacts of one-way streets. The decline in pedestrians and bicyclists can increase crime rates on the street due to loss of “citizen surveillance.”
Increased Imbalance in Traffic Volumes. One-way streets, which tend to be created as coupled pairs, typically cause an imbalance of traffic volumes, as the direction heading toward job concentrations tends to see rather large volumes during morning rush hour, and the direction heading away from jobs tends to see these large volumes in the evening rush hour.
Increased Environmental Injustice. Some have argued that because of the expected harm that one-way streets bring to residential neighborhoods, such a street conversion tends to occur most often in lower-income neighborhoods where there is less political clout to stop such a conversion.
Difficulty in Entering or Exiting the Street. Higher average motor vehicle speeds tend to make entering and existing the street more difficult and unsafe for a motorist, as reaction times or gaps in traffic flow tend to be smaller.
Increase in Pedestrian Discomfort. Because higher motor vehicle speeds feel more dangerous, pedestrian discomfort tends to increase on one-ways. In addition, the higher motor vehicle speeds create increased noise pollution levels, further degrading the pedestrian ambience of such streets. Intimidation and stress felt by the motorist, pedestrian and bicyclist tends to increase on one-way streets. Both motorists and pedestrians are less able to interact with, or enjoy, the streetscape around them at higher motor vehicle speeds, which is tragic because enjoying the journey is an important part of enjoying life.
Increase in Inconvenience. Backtracking or circuitous travel increases with one-ways, as the most direct route to a destination is often made unavailable. This problem is particularly likely for newcomers to a community who are unfamiliar with the local road network. Frustration and ending up “getting lost” are a common experience for a visitor to a community characterized by a great many one-ways. (Rick Hall, of Hall Engineering, indicates that one-way backtracking tends to more than counter-balance any expected time saving benefits that one-ways provide to motorists.) Backtracking is also made more likely because higher average motor vehicle speeds lead to an increase in the motorist not seeing his destination until he or she has passed it.
Increased Inducement to Sprawl. By increasing average motor vehicle speeds, one-way streets promote sprawl residential development. Because people tend to have a “travel time budget” (the amount of time a person is willing to allocate to a daily commute), higher speeds mean that it is possible to live in more remote locations and still remain within the travel time budget.
Increase in Moving Violations. Because one-way streets often require indirect, out-of-the-way travel, some travelers (motorists or bicyclists) will occasionally violate traffic laws by traveling the “wrong way” on a one-way street, particularly if the distance is short or the perception of being “caught” is low. In addition, a number of travelers will unintentionally travel in the wrong direction because they don’t realize the street is one-way. This is especially true for newcomers to a community.
Increased “Barrier Effect.” One-way streets can result in a declining number of pedestrians, bicyclists and transit users. As the average speed of motor vehicles increases, the street becomes increasingly unsafe for non-motorists (at least the perceived lack of safety). Pedestrian and bicycle travel on such streets therefore declines as walkers or bicyclists either seek out more welcoming streets, or opt not to walk or bicycle at all.
Non-motorists, in this case, are fleeing due to a phenomenon known as the “barrier effect,” where real or perceived barriers discourage or prevent use of a product or facility.
Increase in Motorist Impatience. One-way streets tend to increase motorist frustration, in part because the reduced friction of the one-way creates the expectation that the street should now be entirely free of delays. Any slowing down or stopping obligated by traffic signals or vehicle turning movements is therefore more likely to induce dangerous “road rage” reactions and dangerous rudeness by motorists. In a powerful, high-speed motor vehicle, a driver becomes extremely dangerous to his- or herself and others when they are induced to feel impatient, enraged, or rude. This is particularly unsafe for senior citizens and children.
Reduced Safety. When two-way streets are converted to one-way streets, there is typically an increase in the number of travel lanes moving in the same direction. When this happens, safety for the pedestrian can decline dramatically due to the “multiple threat” crash. This pedestrian crash risk occurs when a street contains two or more travel lanes moving in the same direction.
While one of the few known studies of one-way safety impacts has found a dramatic decline in pedestrian deaths and injuries on one-ways (a study I don’t have the title of, but authored by Charlie Zeeger in 1973, I believe), the perception of higher-speed motor vehicle travel to the motorist, bicyclist of pedestrian is increased danger. Some have pointed out that one-way streets can be dangerous when a pedestrian, bicyclist or motorist becomes disoriented and forgets which direction the one-way street is heading. At higher speeds, crashes that do occur are more severe.
Note that it simply feels more dangerous trying to cross a higher speed street, or ride a bicycle on a one-way.
Indeed, the safest streets in a community, counter-intuitively, tend to be give-way streets. These are two-way streets (with on-street parking) that are so narrow that motorists are compelled to drive slowly, attentively, and courteously. The motorist must “give way” when another motorist approaches from the opposite direction.
Increased anxiety and danger are not only experienced by pedestrians and bicyclists, but also motorists. When other motorists are driving faster, more impatiently and inattentively, one feels rushed when driving a motor vehicle. “Will the guy behind me be hostile if I slow down to look for a street sign or make a right turn?” “Am I driving too slow?”
Another danger for the motorist driving in a community with a large number of one-way streets is the increased possibility of turning onto another street and assuming it is one-way rather than two-way. If the assumption is wrong, the motorist is in danger of getting into the incoming traffic lane, or not looking both ways when entering the new street.
Why do cities focus so exclusively on improving suburbs, while at the same time hurting downtown neighborhoods? Suburbs almost never have large, high-speed one-way streets, as suburban residents are aware that such streets harm property values.
There is very little that is more important for city street design than obligating slower-speed, attentive, patient, courteous driving by motorists. The lack of well-behaved driving is toxic to city health.
According to Ecologically Sustainable Design Pty Ltd (2005), “there is less evidence of North American towns undertaking rigorous … investigations into the potential benefits of undertaking conversions [from one-way to two-way]. Rather, it has become widely accepted amongst urban regeneration practitioners that virtually all town centre conversions to two-way streets will be beneficial; it is now more a matter of identifying the range of complimentary improvements needed to catalyse the best returns from the conversion.”
What conditions are most important in improving conditions for bicyclists and pedestrians? I would suggest the following:
1. Reduce the speed differential between cars and bicycles/peds. On slow-speed streets, bicycling and walking tend to be extremely safe and comfortable.
2. Increase the number of bicyclists/peds. There is safety in numbers. A large number of bicyclists or pedestrians sends a very clear signal to non-bicyclists and non-pedestrians that bicycling and walking is safe, hip, practical and fun.
3. Minimize the distance that bicyclists or pedestrians must travel between home, work, shopping, recreation and other daily needs.
For each of these, one-way streets degrade the condition.
One possible benefit that one-way streets can provide in the quest for better urbanism, as I noted earlier, is that they can create the opportunity to establish a very narrow, human-scaled street, if the street is no more than a single-lane street. This has been done quite well in European cities. However, there may not be a practical way to achieve such a quality one-way street in America because of the enormous size of vehicles here, which tends to obligate us to build over-engineered, overly-wide, multi-lane one-way streets.
If the objective of the community was narrowly focused on maximizing the speed and volume of cars on a street, there is a reason to create a one-way street.
However, if the objective was to improve safety, comfort, convenience, quality of life, economic health, and transportation choice, two-way street design is nearly always essential.
Note: The above is largely based on my personal observations. A few items are based on comments I have seen from colleagues, and research I have seen. Some of citations should be checked for accuracy.
My latest book, The Car is the Enemy of the City (WalkableStreets, 2010), can be purchased here.
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Ecologically Sustainable Design Pty Ltd (2005). Summary Report on the conversion of One-way Streets to Two-way Streets in North American Town Centres. Victoria, Australia.