>>1825225They are locked and modern signal controllers use password or pin protection, they're basically large computers. Only in electromechanical systems, such as in Philadelphia, could you directly tamper with the signal timing but you'd need to know how to do it. The older ones literally use pins on a rotating dial (dial = cycle length, usually 60 seconds) to know when to trigger different signals. If you stand next to one you can actually hear it ticking.
