A new report compiled by the American Transportation Research Institute (ATRI) indicates average marginal cost per mile declined 6% in 2015 versus 2014 due almost completely to low diesel fuel prices.

The group said average marginal cost per mile dropped to $1.59 in 2015, down from $1.70 in 2014 – largely attributed to the steady fall in diesel prices experienced last year.

Yet ATRI also pointed out that driver costs – including their wages and benefits – first time since the group began collecting such data in 2008 now represents a higher percentage of overall trucking costs than diesel fuel.

One new addition ATRI’s report this year centers on fleet-wide fuel economy, fleet operating speeds, plus the relationship between speed limiter use and fuel economy.