A car park full of autonomous vehicles (AVs) could accommodate up to 62% more cars than a conventional parking area, according to research from the University of Toronto Faculty of Applied Science and Engineering.

Positioning the AVs in a solid grid rather than a traditional ‘island’ that provides space for drivers to access their vehicles and cars to pull out allows for a much greater capacity for vehicles.

“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 senior author of the study 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.”

The researchers created a computer model to simulate the effects of various layouts in an AV car park. They then used an algorithm to determine the optimal size of the grid, maximising storage while minimising the number of moves required to extract any given car.

“There’s a trade-off,” said lead author from the Department of Civil Engineering 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.”

The team’s analysis showed that for a given number of cars, a well-designed AV car park could accommodate 62% more cars than a conventional one. With some dimensions, they were able to increase the capacity by as much as 87%.

This improved use of space could translate into much smaller car park footprints, provided the total number of cars that need to park in them remained constant.

Roorda hopes that public parking authorities will be able to use their design approach to enhance urban spaces.

“Right now, our downtown cores have giant municipal parking lots next to major attractions,” he said.

“AVs could allow us to both shrink and relocate these parking lots, opening up valuable space in cities.”

Another advantage is that the design is flexible and, according to co-author Sina Bahrami, new parking lines would not have to be painted if demand changed.

“Instead, the operator can just signal the cars to rearrange themselves,” he said. “It will take longer to retrieve your vehicle, but you will fit more cars in.”

However, the team cautioned that an unwanted side-effect of an AV car park could be an increase in traffic congestion.

“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.”

Another disadvantage is that the designs only work for car parks exclusively for AVs, rather than a mix of AVs and conventional vehicles.

The design is also dependent on a large number of AVs being on the road, which the team is unable to predict.

“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.”

The findings were published in journal Transportation Research Part B.