This sign popped up recently along southbound Highway 101 south of downtown Windsor, but if you tune in to the station, all you get is static. Click to enlarge. Road Warrior reader photo.

The mystery over a Highway 101 traffic alert sign in Windsor has been solved.

After a couple of Road Warrior readers recently reported seeing the sign on southbound 101 just south of downtown Windsor and noting that the 840 AM radio station yielded only static, we called Caltrans. There, a spokesman reported he had checked around Caltrans and had come up empty-handed, although he did find another Caltrans official who himself was wondering about the sign. He said he’d call us if he found out. This morning, he did.

Spokesman Robert Haus said the emergency message sign was mistakenly activated because of some electrical glitch and was turned off on Monday.

He said Caltrans erected the sign some time ago knowing that with all of the Highway 101 widening work, now in Rohnert Park, Cotati and Petaluma, that at some point it might come in handy to alert drivers to traffic problems ahead. He said he was unaware of the sign ever being activated for a traffic alert, but it’s ready to go now in case there’s a need.

The 840 radio is a local, low-powered station, he said.

Editor’s note: Many of the reader comments below were prompted by our earlier blog seeking information about the sign.