Low-Value Car Trips

Environmentalists rightly oppose road widening because it will promote sprawl, but grudgingly (?) end up admitting, when push comes to shove, that road widening or turn lanes will reduce air pollution and gas consumption. Widening a road is not all bad, according to this view.

As a result, the homebuilding and road widening lobby has regularly been successful in their efforts to gain political support for widening roads. Many environmentalists, interest groups, and elected officials believe that we need to expand roads and intersections and parking to reduce gas consumption and air emissions.

The “stop and go” problem is correct (ie, that “stop and go” traffic increases air emissions), except for one thing: It applies only to individual cars. When we apply eased car travel to an entire community of drivers (in a community where roads and parking are free to use), we find that many new car trips are artificially induced.  The extra trips would not have occurred had the car travel and parking not been so easy and cheap.

In a ground-breaking worldwide study of cities in 1989 (Cities and Automobile Dependence),  Jeffrey Kenworthy and Peter Newman came to a startling, counterintuitive conclusion: cities that did not spend enormous amounts of money to widen roads and ease traffic flow showed lower levels of air emissions and gas consumption than cities which went on a road-widening, ease-of-traffic-flow binge. This was true even though those communities which did not spend large amounts on widening often had high levels of congestion.

The reason is that nearly all roads and parking spaces are free to use. There is almost never a need to pay a toll to drive on a road, or pay a parking meter. Free-to-use roads and parking inevitably encourage low-value car trips. That is, trips that are of relatively low importance, such as a drive across town on a major road during rush hour to buy a cup of coffee.

The most effective way to reduce low-value car trips is to charge motorists for using the road or parking space by charging for use either by electronically tolling roads or by charging an increased price for the parking. Toll roads and priced parking are very equitable user fees. The more you use a road or parking space, the more you pay — precisely and uncontroversially like we do with electricity use. In doing so, motorists are more likely to use the road or parking space only for the most important car trips (that is, more efficiently), such as the drive to or from work, or medical emergencies, for example.

When roads and parking spaces are free to use, however, they become congested quite quickly because of all the “low-value” car trips on the road.  Unfortunately, it is very difficult, politically, to charge motorists for using a road or a parking space. The result is that almost no road or parking space is tolled or priced.

On the other hand, a consequence of moderate levels of cars crowding a street is that a great many motorists decide in both the short- and long-term to do something else. They opt to use a more free-flowing road. They use transit, walk, or bicycle. They travel at non-rush hour times, or pay a toll to use a managed lane. In the long run, many will move to a location that is closer to their daily destinations as a way to avoid the slower road. And as Kenworthy and Newman found in their worldwide study of cities, this means that cities with slower car travel see less air pollution and less gas consumption because so many low-value car trips have been eliminated by the car crowding.

Note that transportation is a zero-sum game: each time we improve motorist comfort or convenience by widening a road, adding a turn lane, making a road a one-way street, adding more free parking, or synchronizing traffic signals, we reduce the comfort and convenience and safety of transit, walking, and bicycling (car travel, in other words, is “exclusionary,” because easing car travel creates barriers for non-car travel). More trips by car – rather than by transit, bicycle, or foot – leads to more gas consumption and air emissions. Ironically, widened free roads, larger amounts of free parking, and other techniques to ease car travel make the experience worse for drivers as well, because the induced car trips quickly create congested road and parking conditions.

By far, the most effective path to a reduction in car dependence, reduced air emissions, reduced gas consumption, reduced sprawl, more transportation choice, better quality of life, more public health, less traffic injuries and death, less sprawl, a better economic environment, lower taxes, and more civic pride is to (1) take away the excessive amounts of space allocated to cars by narrowing roads and shrinking parking areas, (2) slowing cars, (3) shortening distances to destinations, so that walking and bicycling are more likely, and (4) removing the many large subsidies of car use. Cars slowed moderately with human-scaled street dimensions, more compact development, and the removal of car subsidies for driving, is a recipe for a better community, a better quality of life, and a better environment.  Particularly in a town center (less so in the more drivable suburbs), roads should be designed for humans.  Priority in terms of the timing of signal lights, access, safety, and speed of travel should be given to pedestrians, bicyclists, and transit riders, not cars.

In existing and emerging town centers, slower car travel, smaller street and parking lot sizes, and fairly administered pricing of roads and parking each maximize travel choice and transportation efficiency. These tactics minimize excessive car dependence and low-value car travel. The tactics maximize the efficiency of street and parking lot use. All forms of travel therefore benefit – pedestrians, transit users, bicyclists, as well as motorists – and air emissions are minimized.

About Dom Nozzi

Urban designer, Complete Streets instructor, smart growth specialist, town planner, walkable streets and bikeable streets and trails specialist, writer, editor, public speaker, world adventurer, skier, kayaker, SCUBA diver, bicyclist, hiker, dancer, book reader, cook, urbanist.
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