PROVO (AP) — Every evening in the weeks leading up to Christmas, a loud steam whistle echoes through Heber Valley announcing the departure of the North Pole Express.

While pajama-clad children and their parents sip hot cocoa in train cars warmed by coal fires, a small crew works in the cold, behind the scenes, to make it all happen.

The crew at the Heber Valley Railroad has worked out a precise checklist of tasks that must happen before the passengers arrive. Work starts four hours before departure, making sure the generators are gassed up and that the wood and coal burning stoves that heat the cars are lit.

Two hours before departure, the engineers inspect and start the locomotive, check all the fluids and charge the air brakes.

One hour before departure it is time to start making hot chocolate. Each train ride carries about 62 gallons.

"It's a very detailed schedule," says Craig Lacey, executive director of the Heber Valley Railroad Authority. Lacey left a well-paying, secure job to come work on the railroad in 1983.

"I had the opportunity to ride locomotives on mainline trains while I was in high school," Lacey said. "My mom said I was born 50 years too late, and I think all of us are like that. ... We're all railroad buffs."

Conductor Devin Lloyd is a BYU student who spends as much time as he can spare working on the trains.

"When I was in second grade, I said I'd be a train engineer and then I'd retire and work on the Heber Creeper," Lloyd said. "Well, I just skipped right to my retirement."

Lloyd describes his job as living out a childhood dream. "I'm working with stuff I've been fascinated with my whole life."

Many of the locomotives and train cars are from the early 1900s, and it's time-consuming to work with them.

"It's labor intensive just keeping things running sometimes," engineer Bryan Morris said. But the historic equipment is what attracted many of the railroad's crew.

"I fired up my first steam engine here when I was 17," Morris said with a grin. Since then he has spent 15 seasons on-and-off working on the railroad.

While the Heber Valley Railroad runs all year, The North Pole Express, based on the children's book "The Polar Express," is one of the most popular attractions.

In the weeks leading up to Christmas, the train runs twice a day during the week and three times on Saturdays, ferrying more than 430 passengers on each trip to the North Pole.

Santa boards the train for the ride back, stopping to greet all the children and present them with one of the magical bells from his sleigh.

The ride is a festive affair for the passengers in the train cars, but for the crew the job of keeping everybody safe is serious business.

Like any railroad company, the Heber Valley Railroad exists in an industry of tight regulations. Tests, inspection logs and precise schedules are a staple of the job.

"We're in the entertainment business, but we're operating in the regulated railroad environment," Lacey said.

Balancing more than 400 passengers, entertainers and turn-of-the-century railroad equipment all at the same time is not easy.

"There's never a dull moment," Lacey said. "We all wear different hats. Sometimes I'm driving a truck, shoveling coal, doing paperwork or driving the train. We have to be very versatile and ready to respond at any moment."

The work is physically demanding and stressful, but the reward is worth it for everyone involved.

"When you see the kids' faces when they see Santa, that's a big part of the payoff," Lacey said.