Orders of Class 5-7 trucks, buses and RVs rose 11 percent in January over the same month a year ago, yet came in below expectations, according to ACT Research.

The month was a 22 percent decline from the fourth quarter peak and suggests lower backlogs moving forward, said Kenny Vieth, ACT's president and senior analyst. The firm tracks orders that have been placed for trucks that haven't been built to measure demand. Class 5-7 orders came in at 17,800 units for the month.

"January’s medium-duty orders fell slightly below build expectations, suggesting that backlogs are likely to be 1,000 to 2,000 units lower when the complete data set is compiled" later this month, Vieth said.

Growth in medium-duty truck sales is expected to slow in 2015, said Steve Tam, ACT's vice president of the commercial vehicle sector.

"We expect modest growth in 2015, probably about 4 percent above 2014, so while medium-duty sales are still growing, the rate of growth has slowed," Tam told Work Truck.