CSOs such as Zipcar and City CarShare is a trend that is on the rise

As transportation planners, we are well aware of the difficulty of convincing drivers to leave their cars behind. The automobile has been the overwhelmingly dominant mode of transportation in the U.S. for more than 50 years. Transit systems often find themselves competing for the same car-deprived market share. A new commuter rail line or ferry service is more likely to be pulling riders off of existing bus lines than getting them out of their cars. It is not hard to see the main reason for this. The peculiar nature of the automobile makes it the one transportation option that presents the user with high fixed costs and low marginal costs. The major costs of auto transportation - car payments and insurance - are largely independent of the miles driven. The variable costs that increase with mileage - the price of gasoline, parking, and routine maintenance - are (at least until recently) very low. The perverse logic of this is that, in spite of car ownership being a major financial drain, once someone owns a car, their incentive is to drive it as much as possible. The marginal cost of a 10 mile trip by auto is almost always going to be lower than marginal cost of the equivalent trip by transit, even if the average cost is higher for the auto. Since we all know the economic maxim "sunk costs don't count," the auto trip will always be the consumer's choice. This is especially true when the trip includes more than one person, and especially when the value of time is factored in. Fortunately, one of the more innovative trends in transportation seems to be promising a way to partially address this issue. This trend is the rise of Car Share Operations (CSOs) such as Zipcar and City CarShare. The concept of commercial CSOs can be traced back to the early 1970s but they only became viable operations in the past decade with the rise of the World Wide Web. Much like the VCR/DVR evolution, the advantages of CSOs over traditional car rental agencies like Hertz and Avis may not be immediately clear. The CSOs succeed by combining the following four advantages over the rental agencies: 1. Convenience - CSO members can use the web to access their account, and reserve a vehicle in less than 90 seconds. 2. Proximity - instead of requiring the traveler to visit a central garage to pick up the vehicle, the cars are dispersed at parking locations throughout the city - the traveler can easily pick up their vehicle near their home, their workplace, or a transit station or airport. 3. Variety - the member can choose the specific type of vehicle they want on a trip-by-trip basis - compact economy cars when they are alone, larger sedans when they have a group to transport, or an SUV/minivan when they are moving furniture. 4. Hourly rates - CSOs allows members to reserve a car for as little as one-half hour for approximately $6. It is difficult for rental agencies to offer these micro-units of service - with their high overhead for customer service agents, reservations desks, and parking garages, they need the high volume of daily and weekly rates. 5. According to Zipcar, each shared vehicle is estimated to take 15 privately owned vehicles off the road. By offering customers convenient access to a vehicle whenever they need it, many people for whom car ownership is not an absolute necessity are more likely to give up ownership of their optional car and rely on the CSO. Once they do this, the automobile is now competing on an even economic footing with other modes - a very low fixed cost (the price of an annual CSO membership) combined with a high marginal cost (the hourly rental rates). This gives the CSO member the incentive to limit their auto use to those trips when it is the only reasonable alternative. As transportation planners, the implications of this are significant. Developers can team with CSOs to provide vehicles for new residential buildings, thus reducing the required parking. Transit agencies can provide parking for shared vehicles at commuter rail stations, encouraging travelers to "ride and drive" instead of drive the entire distance. CSOs are currently an urban phenomenon, but there is potential for expanding into the auto-dependent suburbs, where they could give two-car families the incentive to become one-car families, and three-car families the incentive to become two-car families. Imagine a shared car parked along a suburban street shared by all houses on that block. The same logic for reducing auto trips would apply, although probably with diminishing returns. Finally, the success of CSOs suggests their expansion beyond automobiles to other items where high capital costs combined with infrequent usage make private ownership a sometimes dubious proposition. Bike-share services, which already exist in cities such as Paris and Cologne, Germany, seem to be the next logical step but it is easy to imagine a future of hourly rentals for boats, tools, and lawn equipment. Mike Cohen is project manager for Sam Schwartz Engineering, New York, N.Y.