Rush hour 2026 – your self-driving car abruptly shuts down, blocking traffic. Gridlock builds on surrounding streets as hackers paralyze all area traffic by randomly stranding Internet-connected cars.

Researchers at the Georgia Institute of Technology and Multiscale Systems Inc. have simulated hacker-induced widespread havoc to expand the discussion on automotive cybersecurity to include potential mass mayhem.

Data breaches have soared, and objects becoming hackable could convert the rising cyber threat into a menace.

“Unlike most of the data breaches we hear about, hacked cars have physical consequences,” says Peter Yunker, study co-leader and assistant professor at Georgia Tech's School of Physics. State actors, terrorists, or mischievous individuals could commandeer parts of the Internet of Things (IoT), including cars.

Study co-leader Jesse Silverberg of Multiscale Systems Inc. says cars tend to have a centralized computer system that runs everything from the engine to the satellite radio, so “if you can get into one, you may be able to get into the other.”

Freezing traffic

In car-hacking simulations, researchers froze traffic in Manhattan nearly solid with minimal effort.

“Randomly stalling 20% of cars during rush hour would mean total traffic freeze. At 20%, the city has been broken up into small islands, where you may be able to inch around a few blocks, but no one would be able to move across town,” says David Yanni, a graduate research assistant in Yunker's lab.

Because hackers need to compromise only 20% of cars to create gridlock, if 40% of vehicles were connected, hacking half would suffice. Even hacking 10% of cars at rush hour would debilitate traffic enough to cripple emergency vehicles.

In other cities, things could be worse.

“Manhattan has a nice grid, and that makes traffic more efficient. Looking at cities without large grids like Atlanta, Boston, or Los Angeles, we think hackers could do worse harm because a grid makes you more robust with redundancies to get to the same places,” Yunker says.

The researchers considered only if roads would be blocked or clear, excluding factors such as public panic or drivers leaving their cars and becoming pedestrians, that could worsen hacking damage. Nor did they consider hacks targeted at key locations to maximize trouble.

“In many cases, blocked roads spill over traffic into other roads, which we also did not include. If we were to factor in these other things, the number of cars you'd have to stall would likely drop down significantly,” Yunker adds.

The study doesn’t comment on the likelihood of such a hack, researchers simply calculated the scale of a hack that would shut down a city.

Potential solutions

“Split up the digital network influencing the cars to make it impossible to access too many cars through one network,” says lead author Skanka Vivek, a postdoctoral researcher in Yunker's lab. Ensuring that adjacent cars couldn’t be hacked at the same time would decrease the risk of traffic shutdowns as well.

Georgia Tech

Multiscale Systems Inc.