A familiar sound blares once again in Potterville.
It's the sound of trains rolling right through downtown -- past the spot where crews have been clearing up debris, scrapping traincars and re-laying track since early Friday morning.
The crews are cleaning up after Thursday night's 15-car train derailment.
The heavy-lifting draws its share of onlookers. Among them, Stanley Michels of Mason.
"I just wanted to get some pictures of the railcars in the ditch. I'm a railroad fan," Michels said.
He says the recent derailment -- four years to the month after another one -- runs afoul of an adage in the railroad business.
"(When) a train derails, it will never derail here again," Michels said. "It's one in a million."
The railroad's preliminary investigation has concluded the culprit was an overheated wheel bearing on one of the cars.
"Yeah, but there are four detectors," Michels said.
Michels is talking about so-called "hotbox" detectors. He knows about them, because he's more than just a rail buff. Michels worked for the Norfolk Southern railroad in Lansing for 41 years, most recently, as a yardmaster. He tells us how these hotboxes work.
"When the train goes by there, the heat of the wheel sends a message inside and it comes on and tells the engineer he's got ... hot wheels."
"There are four hotbox detectors on this road between Durand and Lansing. There's two between here and Battle Creek," Michels said.
A spokesman for the Federal Railroad Administration tells us these "hotboxes" exist -- and they work just like Michels told us.
Earlier reports stated the train passed over at least one of the "hotboxes" before the derailment. But for whatever reason, there was no alarm.
The clean-up -- and Canadian National Railway Co.'s investigation into the derailment -- continue.