Those among us “of a certain age” may remember the Jetsons cartoon depiction of flying cars. While this era of personal rapid transit is not upon us, that of driverless cars soon will be.
Driverless cars represent a revolution in transit. However, they are not the sole solution to congestion, and we should not expect automated low-capacity vehicles to replace the need for high-capacity fixed guideway systems such as bus rapid transit and light rail.
The Singapore MIT Alliance for Research and Technology (SMART) has extensively modeled driverless car deployment. With all cars driverless, its models showed a nearly two-thirds decrease in the number of cars needed for transit. However, the actual number of miles driven by automobiles increased, as did use of secondary and residential streets.
Rebalancing the fleet is no trivial task. Columbia University corroborates this conclusion with a study of three different sizes of U.S. cities. These and other studies demonstrate that driverless car technology can increase urban traffic congestion if it is seen is the sole solution to transit.
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The International Transit Forum has also developed intricate transit models that come up with similar results when driverless cars are deployed; while the number of vehicles needed dramatically decreases, total vehicle miles traveled goes up.
As modeled for Lisbon, Portugal, full deployment of single-passenger driverless vehicles more than doubled vehicle mileage in the absence of high-capacity public transport.
Sharing driverless cars with up to five people per trip increased total vehicle mileage by only a quarter. Better still was a fleet of driverless taxis that get people to and from high-capacity fixed guideway transit hubs; when shared driverless cars were teamed with about one in four travelers using rail transit, vehicle miles increased only marginally rather than doubling with solo cars and no rail transit. Models of a mixture of driverless and traditional human driven car traffic were shown to increase the number of cars on the road during peak travel as well as increase overall car mileage in all but one scenario: traditional cars and shared driverless cars and working in conjunction with high-capacity fixed guideway transit.
Driverless cars promise increased safety and optimize vehicle utilization and parking while dramatically decreasing consumer cost per mile. They also make more efficient use of road space with “platooning” allowing them to ride safely in close formation. This confers a significant advantage on highways, but not quite so much in complex urban settings, particularly if we want these cars to interact safely with non-automated technology such as bikes and walking shoes. With that in mind, driverless vehicles might make more sense being deployed locally to RDU and RTP than either downtown Durham or downtown Chapel Hill.
Driverless vehicles represent a transformative technology. In small towns with open traffic lanes, they could eliminate the need for local public transit. However, in areas already suffering with congestion issues, that is not the case. Here in the Triangle, driverless technology will dovetail nicely with Go Triangle’s comprehensive regional transit plan by increasing access to the Durham-Orange Light Rail line that is planned to run between the largest employer in the Triangle and the largest employer in Orange County.
We should not delude ourselves thinking that vehicle automation will allow us to pave our way out of our growing congestion. So, until George Jetson arrives and unfolds his briefcase into a flying car, let us pursue comprehensive and integrated transit solutions and not sit on our hands – or sit stuck in traffic.
Tom Farmer lives in Chapel Hill and has been a Go Triangle commuter since moving back to the area in 2009.