» To what degree can we rely on people getting into strangers’ cars to reduce the congestion on our highway networks?
Outside of the biggest, densest cities, transit generally underperforms; with smaller populations, less significant destinations, more diffuse congestion, and far more available parking, there is often little motivation for people to abandon their cars in favor of jumping on the bus or the train. As a result, the work commuting mode share for public transportation in most metropolitan areas in the U.S.is less than 5% (only five regions have shares above 10%).
Carpooling, on the other hand, attracts more than 7% of work trips in all major metropolitan areas. In many places, where public transportation options just are not particularly appealing, sharing an automobile with another person can be an excellent commuting alternative, especially for people who cannot afford to own their own vehicles.
But how useful can carpooling be in answering a city’s transportation demand? Could its use be expanded significantly to encourage more people to get out of their single-passenger automobiles — without having to set down the millions of dollars required to build and maintain transit systems?
Last weekend at the Congress for the New Urbanism’s Madison conference, Paul Minett of New Zealand’s Trip Convergence made a compelling case. Most people drive their cars to and from work, but leave them sitting unused 95% of the time, he argued — we should make their use more efficient. In many cities like his own Auckland, 94% of road space is used by single-occupancy automobiles. And transit’s frequently minuscule mode share means that even if it doubled its capacity over the next ten years, it would still account for few overall commuters.
Mr. Minett advanced the notion that ridesharing — a system by which people get out of their own cars and essentially share a vehicle with other commuters taking similar routes to work — could triple or quadruple the capacity of existing roads, all without any added physical investment, the stuff no one can afford anymore. Unlike traditional carpooling, which requires people who know each other to share itineraries, ridesharing allows trusting strangers to save the cost of commuting.
From an urban environment perspective the benefits of encouraging more people to choose to ride together rather than drive separately are indeed significant: Just like with transit, reducing the sheer number of cars entering the central business district at rush hour can play an important role in cutting the number of lane-miles required on the roads downtown and throughout the city, and it opens up more developable land for buildings rather than parking. And the reduction in overall transportation infrastructure necessary to keep a city functioning means fewer expenditures by local governments.
Problems that have made ridesharing difficult for many people to adopt in the past have revolved around the issue of coordination. Finding people who share similar routes is not always easy, and the result can be frustrating waits on the side of a busy road, hoping someone with a sign advertising a similar destination shows up. But new technologies that virtually everyone can take advantage of through devices like smart phones solve many of those problems. They allow people to find others who are traveling the same routes as they are, thus reducing the difficulty of aligning origins and destinations.
In some cities like Washington, D.C., where ridesharing is referred to as “slugging,” as a mode it has made a successful dent into congestion and reduced the individual cost of toll roads. In the San Francisco metropolitan area, 10,000 people “casual carpool” everyday. If a lack of tax funds for capital investments in transportation is a problem, thus encouraging the charging of people to use highways, making ridesharing work well in places with few transit alternatives could reduce opposition to tolling.
Cheaper “transit” options, like downtown circulators and bike and car sharing, could ensure that in central city areas people are able to get around during the day without automobiles. As part of any city’s overall effort to encourage transportation alternatives, ridesharing should clearly be considered.
In his speech, Mr. Minett admitted that there remain significant obstacles to the wide-scale introduction of ridesharing. The ease of jumping in a car or — when it’s available — catching the next bus or train is partially based on the independence of others those modes afford.
The effort to expand ridesharing’s use has other structural difficulties, namely the fact that any corridor that works well for ridesharing would probably work better for a good transit line. Fundamentally, a place where ridesharing is appealing is one where either significant congestion exists and thus where a city or state implements carpool-only lanes or where traffic control measures like tolling are implemented. In the first case, people want to share a ride because it reduces their trip times (because they can travel in the free-flowing carpool lanes) or because it reduces their costs (because they can split the toll with the others in their car).
In other words, cities that suffer from few highway backups (and which therefore have no carpool lanes or tolls) provide their citizens few incentives to share rides (or use transit).
On the other hand, in most corridors where there is significant congestion, good transit is arguably in demand and necessary to attract people out of their cars. Is it a surprise that the cities with the lowest carpooling mode shares in the U.S. are those with the highest transit mode shares? As long as it is appropriately designed, with high frequencies of service and good accessibility, transit is the more popular option.
Finding the right spot for a ridesharing program, then, is likely no simple matter.
Image above: Carpools only sign, from Flickr user Richard Drdul (cc)