Article about the system that allows the normal operation of traffic lights to be preempted, which is traffic signal preemption, this is often to assist emergency vehicle. This article includes implementation, vehicular device types and, railroad preemption.
Article which defines traffic signal preemption, describes how it is implemented, etc. "Traffic signal preemption is a type of system that allows the normal operation of traffic lights to be preempted, often to assist emergency vehicles"
Video length: 1 min 7 secs. A short video regarding traffic control systems and how it helps improve the response time.
"It's more than good driving and good luck that gets emergency vehicles through traffic snarls. The city of Birmingham has a computer system that changes red lights to green to expedite Fire Department vehicles along a designated route."