As reported on Vox, using only a laptop and wireless card that operates at the wirelessly operated traffic light frequency (5.8 gigahertz), the scientists controlled a number of intersections within Michigan. By hacking into the system, the study was able to "alter the normal timing pattern of the lights, turning all the lights along a given route green, for instance, or freezing an intersection with all reds."
About 62 percent of traffic lights throughout the nation are connected to ensure communications with central operations hubs to optimize traffic congestion. However, these systems currently lack the architecture for security and preventing attacks.
According to Joseph Stromberg, once the researchers accessed the network, "they could use a series of simple commands to freeze the traffic lights in their current state, or turn all lights red, or alter the timing of the light changes. The one thing they couldn't do was give all sides of an intersection a green light."