Chicago ? You know Dasher and Dancer, Prancer and Vixen … but how about an open subway car that pulls Santa Claus and his sleigh through grimy, dark tunnels at 50 mph?

The brave Santa is just one feature of the Holiday Train, which zips through the city’s subway and on top of its elevated tracks, surprising commuters and delighting youngsters.

Holiday music booms over the speakers, the hand poles are wrapped in red and white paper to look like giant candy canes, and jolly ol’ St. Nick — wearing his seat belt, of course — rides on a sleigh placed on an open flatbed car in the middle of the train.

The train, which costs a regular $1.50 fare, alternates trips on six of the city’s seven train lines on weekends and some Mondays between Thanksgiving and Christmas. Its last runs of this season will be today.

The Holiday Train began in 1992 with a few modest decorations on the outside. This year’s version is draped in garland, wrapped in a special seasonal vinyl covering and twinkles with 50,000 lights.

Although a schedule is posted on the Internet, many riders end up on the train by chance. Along with excited children whose parents planned the trip, plenty of sour-faced commuters break into silly grins and laughs when they find their normally drab train car turned into a winter wonderland.

“It’s beautiful!” exclaimed Rochelle Sims as she boarded the train last week after work. Sims looked overhead at the red and green bulbs that had replaced the normal fluorescent glare. “This puts me in the Christmas mood. It makes commuting more fun.”

Santa waves from the Holiday Train as it pulls out of downtown Chicago. He and his reindeer ride on a flatbed train car between the commuter train cars.