Could self-driving cars shrink parking lots? These researchers think so

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On-street parking spaces, underground garages and multi-storey car parks all take up valuable space in increasingly congested city centres.

But the advent of autonomous vehicles promises to change the way parking is used. And a team of researchers in Canada believe they have found a way to demonstrate how autonomous vehicles could significantly reduce the amount of urban space given over to parked cars.

In a parking lot full of AVs, you don’t need to open the doors, so they can park with very little space in between.
— University of Toronto Professor Matthew Roorda

While traditional parking lots are configured for ‘islands’ of cars that can each pull into or out of a spot, say the team at the University of Toronto (U of T), autonomous vehicles will change all that.

A dedicated parking lot for autonomous vehicles (AVs) could resemble a solid grid, they believe, with outer cars moving aside to let the cars on the inside enter and exit.

“In a parking lot full of AVs, you don’t need to open the doors, so they can park with very little space in between,” said U of T Professor Matthew Roorda.

“You also don’t need to leave space for each car to drive out, because you can signal the surrounding AVs to move out of the way.”



With this in mind, the researchers worked to determine the optimal size of the grid to maximise storage while minimising the complexity of extracting any given car.

“There’s a trade-off,” said the study’s lead author Mehdi Nourinejad. “If you have a very large grid, it leads to a lot of relocations, which means that it takes longer on average to retrieve your vehicle. On the other hand, if you have a number of smaller grids, it wastes a lot of space.”

Nourinejad and Roorda worked with co-author Sina Bahrami to design a computer model in which they simulated the effects of various layouts for AV parking lots.

 This animation shows how parking could work in lots dedicated to autonomous vehicles. Cars in the outer rows of the grid can move out of the way to allow cars in the middle to escape. (Image: Sina Bahrami)

This animation shows how parking could work in lots dedicated to autonomous vehicles. Cars in the outer rows of the grid can move out of the way to allow cars in the middle to escape. (Image: Sina Bahrami)

According to their analysis, a well-designed autonomous vehicle parking lot could accommodate 62% more cars than a conventional one, for a given number of cars. The use of a square-shaped AV parking lot, meanwhile, could see that figure increase to as much as 87%, found the team.

The researchers also noted that AV parking lots could have a more flexible design than conventional car parks.

“If demand changes — for example, if you need to pack more cars into the lot — you don’t need to paint new parking spaces,” said Bahrami. “Instead, the operator can just signal the cars to rearrange themselves. It will take longer to retrieve your vehicle, but you will fit more cars in.”

However, the concept of autonomous vehicles driving themselves to a dedicated car park could also introduce negative consequences, say the authors.

“Right now, we have a lot of cars on the road with just one passenger,” said Roorda. “If we locate AV parking lots too far away from major attractions, we could end up with streets crowded with vehicles that have zero passengers, which would be worse.”

In addition, the team aren’t sure when the number of AVs on the road will reach the level required to make use of their designs.

“We’re talking about large numbers of vehicles that can fully drive themselves, with no requirement for a driver to take over if something goes wrong,” said Roorda. “There’s a lot that has to happen before we get to that stage.”