Low diesel fuel prices and increased availability of trucks in the spot market will keep transportation costs down for retailers and manufacturers, while causing pain for the freight and logistics industry, according to industry analysts.

Growth in freight volumes slowed in the final months of 2015 after a strong start to the year. Shippers are having an easier time finding trucks to hire as a result. That’s giving them power to demand cheaper rates, reversing the dynamic seen for much of 2014 and early 2015, when trucking...