By Brian Lutenegger
A pair of recent studies suggests that autonomous vehicles (AVs) will revolutionize how vehicles park when not in use. As a result, parking structures will be able to hold far more vehicles than today, and some existing parking facilities may be repurposed to other uses and to take advantage of valuable urban land. Not mentioned in the studies is the reality that autonomous vehicles will be less likely to be privately owned and will spend far less time parked than today’s vehicles do.
A University of Toronto study compares existing parking structures of today with those designed for AVs. Noting that in the U.S. alone there are approximately 6,500 square miles (an area larger than Connecticut) today devoted to parking, the study suggests how parking structures might be redesigned to accommodate AVs.
AVs do not require human drivers to take their vehicle into the parking facility. This means that driving lanes can be more narrow and auxiliary features like stairs and elevators can be reduced or eliminated. Instead of today’s parking facilities with “islands” containing two rows of vehicles, AV parking facilities can be designed to hold more than two rows of vehicles per island as long as there is a mechanism to avoid blocking in any particular vehicle.
Finding the optimal layout, which varies based on the specific design of the structure, will greatly reduce the need for parking space by an average of 62 percent and a maximum of 87 percent. Their study also shows that square-shaped structures enhance their efficiency of space use. Finally, as demand fluctuates throughout the day, the configuration of the structure could change. The AVs could rearrange themselves to accommodate the new layout. In addition, the authors note, during the transition from human-driven vehicles to AVs, separate parking facilities may be required for each type of vehicle.
While the study provides one of the first examples of optimal parking facility layout, additional research is needed to refine the model around operational planning. Not every vehicle is the same and, as noted above, the most optimal layout for the facility will change throughout the day depending on the number of vehicles currently parking.
A second study also looks at the capacity and optimal geometry of parking facilities for AVs. This study suggests that spatial efficiency—parking spaces per unit area—gains are a more modest 40-50 percent, which ensures that each vehicle is independently accessible. Most of these gains would not require major engineering design changes from today’s vehicles where only the front two wheels pivot.
Reducing the land area reserved solely for parking is a key tool to make cities more livable. By repurposing existing parking into new residential, commercial, or recreational uses, cities will be able to create attractive places where residents and visitors want to spend time.
However, while each vehicle may not be in operation on a 24/7 basis, the deployment of AVs also offers the opportunity to move away from today’s private vehicle ownership model to one of shared vehicle ownership. Instead of remaining parked for much of the day—as most vehicles used for work commuting are today—AVs could be a shared fleet able to pick up and drop off passengers throughout the day. This model would further reduce the need for parking in the core of cities.
Regardless of whether they are moving to and from a parking lot or seeking their next passenger, empty AVs could create significant traffic problems in cities, raising overall vehicle miles traveled—particularly if parking lots are located some distance from busy urban corridors. Careful management of vehicle fleets—whether in parking lots or on the streets—will be key to their successful deployment.
If your state or city has implemented policies to maximize the benefits or minimize the drawbacks of AVs, SSTI invites you to contact us.
Brian Lutenegger is a Program Associate at Smart Growth America.
By Brian Lutenegger