Sales of medium-duty trucks in classes 5-7 increased 15 percent in 2014 compared to the prior year, according to ACT Research.

The medium-duty market wasn't as robust as the Class 8 market, but logged a strong year especially toward the end, said Kenny Vieth, ACT's president and senior analyst.

For the full year, Classes 5-7 net orders totaled 223,250 units, which represented the best year since 2006, Vieth said.

"The order improvement was broad based, with trucks up 15 percent, buses up 23 percent percent, and RVs up 17 percent," Vieth said. "The only negative was step vans, which saw order decline 12 percent." Overall, orders of classes 5-7 vehicles including trucks, buses and RVs rose 12 percent.