For several years a mysterious fleet of tractor trailers loaded with natural gas cylinders has been crisscrossing U.S. roads, and in the dark early morning hours on Sunday, March 3, one drove off a highway near Cobleskill, New York, careened down an embankment, and flipped over. The driver had fallen asleep, according to a New York State police accident report, the truck was demolished, and “several tanks ruptured and were leaking” natural gas. Five nearby homes were evacuated.

For retired New York Department of Transportation commercial vehicle inspector Ron Barton, an alarm bell he had been ringing for months suddenly grew even more urgent. “This is a catastrophe waiting to happen,” says Barton.

The trucks are part of a little-known system of moving natural gas called “virtual pipelines.”