.

Then, do ambulances have a button to change traffic lights?

No, we don't have a magical button that can change the light immediately. Like others have said, we have an infrared strobe on the truck that tell the light that we're “running emergent” (lights and sirens) and if we can't get through the light due to traffic, it'll change the light within 15 - 20 seconds or so.

Additionally, what triggers traffic lights to change? The primary, reliable and most common traffic light sensors are induction loops. Inductive loops are coils of wire that have been embedded on the surface of the road to detect changes in inductance and convey them to the sensor circuitry in order to produce signals.

Also, is there a device to change traffic lights?

The device, called an Opticon, is similar to what firefighters use to change lights when they respond to emergencies. It emits an infrared pulse that receivers on the traffic lights pick up. (Buy your own "traffic control preemptive device" here for just $299.99.)

How do cops make lights turn green?

The use of infrared (IR) light has become more popular than the siren based system. A strobe mounted with the standard police lights sends out an IR signal to turn traffic lights green. A sensor mounted on a traffic light watches for a specific IR flash pattern.