Spot market freight volume remained relatively strong in May, edging down just 1.7% from April, according to the DAT North American Freight Index, based on DAT Solutions' network of load boards in the U.S. and Canada.

Compared to the extraordinary volume of May 2014, freight dropped 27%. However, volume exceeded same-month totals for 16 of the 18 years since the index was established in 1997.

May freight volume dipped 0.8% from April for vans and 4.6% for flatbeds, while refrigerated freight increased 8.1%.

Rates on the spot market followed the trends in volume by equipment type, slipping 1.9% for vans and 0.5% for flatbeds, while reefer rates rose 2.7%, compared to April.

Fuel prices increased from April to May, and the additional surcharge led to an increase in the total rate paid for flatbeds as well as reefers, but the total rate for vans declined month over month despite the surcharge, according to DAT.

On a year-over-year basis, freight volume was down 16% for vans and 41% for flatbeds, but increased 2.5% for reefers, compared to May 2014.

Line haul rates trended up, with van rates adding 4.7%, flatbeds up 2.2%, and reefers rising 2.7%, year-over-year. The total rate declined for all equipment types, however, due to a steep drop in fuel prices and associated surcharges, according to DAT.