A HAWK (High-Intensity Activated CrossWalK) signal is a device used to assist people with safely crossing busy streets. Basically, the signals stay dark until activated, either by pushing a button or an automatic sensor, which directs the person walking or biking to wait for the signal to change and traffic to stop allowing them to cross safely.
For a driver, the HAWK signal appears differently than other traffic lights. Once triggered, it will then go through a series of yellow and red sequences requiring motorists to slow down and stop. After the people walking and biking cross, the HAWK will go dark again, allowing motorists to continue through the intersection.
They've been in use in Arlington for a while, and recently they've debuted in Collin County.