As world economies grow, new cities rise and existing urban boundaries expand, caused by people rising out of poverty and migrating en masse to cities in search of a better living. In the U.S., there are record-low unemployment rates and steady auto sales. This adds thousands of vehicles to streets and highways – frequently creating traffic jams and reducing the overall speed of movement during peak hours.
This situation will likely only get worse in the coming years, especially with the rise of autonomous vehicles, which may add even more volume to the roads. Meanwhile, finding parking spaces in city downtowns is difficult, as an incessant addition of vehicles feeds untenable volumes and constricts road and parking capacity.
Self-driving vehicles of the future may face two possibilities after they have chauffeured their owners to their workplace and need to wait to take them back home. The first option is to find a suitable parking spot that is not far from the destination or pick-up point, while also not being too expensive. The other option is to cruise around the city streets until its next scheduled pick-up.
“Today, the main constraint of using a private car in city centers or even university campuses is parking – both its availability and price. With self-driving cars that constraint goes away as they could just cruise around,” said Adam Millard-Ball, associate professor of environmental studies at the University of California, Santa Cruz. “But that also leads to increased traffic which is concerning. Based on my model, I can say that for large autonomous vehicles of the future, cruising around would be cheaper than finding a parking spot.”
Millard-Ball uses an adaptation of a traffic micro-simulation model that looks at the detailed behavior of each individual vehicle, like the instances of them stopping at a light, changing lanes or being stuck in traffic. The model assumes that vehicles on the road would ideally look to go as fast as possible, while opting for the quickest route to the destination.
“I adapted this model to look at what happens if those cars are programmed to just “kill time.” So what happens at each intersection is that they choose the most congested or slowest street,” said Millard-Ball. The implications of such action are telling, as such idling cars would quickly snowball to create endless logjams. For instance, in a city like San Francisco, only about 2,000 self-driving cars in its downtown streets would be enough to slow traffic to less than two miles per hour.
Instructing the self-driving cars to move outside the city centers for cheaper and more vacant parking spaces would also be a problem. Millard-Ball contended that remote parking lots would have to be very cheap to compete with cruising costs, especially when considering the cost of getting to and from such parking lots. This would also mean acquiring land for parking on the outskirts, which is hard as cities are perennially expanding and real estate prices cannot be contained.
“The fundamental problem is that city streets are underpriced or are not priced at all, making it free for any car to use them. Vehicles take great advantage of this today as cities charge only for the use of parking lots in city centers and do not charge for the driving lanes,” said Millard-Ball. “Congestion pricing would rectify that discrepancy. The idea of congestion pricing is to make it more expensive to cruise around than to park a vehicle.”
Roads are essentially a part of the city’s real estate, and administrations are practically giving it away for free, which is a primary reason for the extensive traffic jams seen daily during peak hours. Charging for congestion costs would alleviate this problem by forcing drivers to account for the full costs of their cruising decisions.
“Congestion pricing would be an excellent course of action for governments to take. This is true even without self-driving vehicles. Economists and environmentalists largely agree that it’s a way to internalize the negative impacts of traffic in an efficient way,” said Millard-Ball. “This is not dictating to anyone how they can drive or how they can use their car. Instead, congestion pricing dictates that if they want to use the street, they have to pay the full cost of that [use] to society.”