Animal crossing signs line roads all across the state. How do the signs with lights know when to turn on?

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The wildlife detection system uses radar to sense large animals, which sets off the warning light. In this case the large animal was the reporter on the shoulder of the road taking a photo of the sign.

WILDLIFE-CROSSING-WARNING-SIGNS
Caitlin Kim/CPR News
This video screen grab shows the zap mat/warning signs combo at work. A deer sets off the lights as it crosses the road.

WILDLIFE-CROSSING-WARNING-SIGNS
Caitlin Kim/CPR News
CDOT Engineer Jennie Schnackenberg points out the system, which involves the sign with lights, a 360 radar and camera and a cabinet control center located about a 25 minute drive outside of Craig, in northwestern Colorado.

WILDLIFE-CROSSING-WARNING-SIGNS
Caitlin Kim/CPR News
A zap mat embedded before a cattle grate helps ensure that animals don't attempt to cross the road in the high fence area, and rather help move them to the wildlife crossing zone area.

WILDLIFE-CROSSING-WARNING-SIGNS
Caitlin Kim/CPR News
A zap mat embedded before a cattle grate helps ensure that animals don't attempt to cross the road in the high fence area, and rather help move them to the wildlife crossing zone area.