Innovative technology costs related to the freight handling pilot test program at ABF Freight impacted operating results of the Asset-Based segment by $7.5 million and $14.4 million for the three and six months ended June 30, 2021, respectively, compared to $4.8 million and $9.3 million, respectively, for the same periods of 2020. The pilot, which began in early 2019, is in the early stages in a limited number of locations. While ArcBest believes the pilot has potential to provide safer and improved freight handling, a number of factors will be involved in determining proof of concept and there can be no assurances that pilot testing will be successful or expand beyond current testing locations. We anticipate innovative technology costs associated with the pilot to impact our Asset-Based operating expenses by approximately $7.5 million in third quarter 2021, compared to $6.2 million in third quarter 2020.
The segment’s operating ratio was also impacted by changes in operating expenses as discussed in the following paragraphs.
Asset-Based Operating Expenses
Labor costs, which are reported in operating expenses as salaries, wages, and benefits, amounted to 46.3% and 48.6% of Asset-Based segment revenues for the three and six-month period ended June 30, 2021, respectively, compared to 54.1% 54.6%, respectively, for the same periods of 2020. The decreases in salaries, wages, and benefits as a percentage of revenue for the three and six months ended June 30, 2021, compared to the same prior-year periods, were partially offset by higher utilization of purchased transportation to meet customer demand for increased shipment levels. The improvement in salaries, wages, and benefits as a percentage of revenue was also influenced by the effect of higher revenues including fuel surcharges, as a portion of operating costs are fixed in nature and decrease as a percent of revenue with increases in revenue levels. Salaries, wages, and benefits increased $53.4 million and $55.2 million for the three and six months ended June 30, 2021, respectively, compared to the same periods of 2020, primarily due to the increase in business levels. The increase in expense also reflects higher expense accruals for certain performance-based incentive plans, year-over-year increases in contractual wage and benefit contribution rates under the 2018 ABF NMFA, and higher nonunion wages and benefits versus the prior-year periods when cost reductions were in place in response to the COVID-19 pandemic, as previously discussed in the Consolidated Results section of MD&A. The contractual wage rate under the 2018 ABF NMFA increased 1.6% effective July 1, 2020, and the average health, welfare, and pension benefit contribution rate increased approximately 2.2% effective primarily on August 1, 2020.
The Asset-Based segment manages costs with shipment levels; however, increased shipment levels, freight profile changes, challenges with hiring an adequate number of personnel, and equipment capacity constraints pressured the efficiency of dock, street, and yard tasks during the second quarter of 2021. Shipments per DSY hour declined 2.8% for the second quarter of 2021, compared to second quarter 2020, primarily due to inefficiencies driven by equipment capacity constraints related to the business growth and the effect of handling a higher number of larger LTL-rated shipments, including an increase in pieces per shipment. For the six months ended June 30, 2021, shipments per DSY hour improved 0.4% compared to the same period of 2020. While the Asset-Based segment has added employees to service the business growth, the segment had to supplement resources with increased utilization of higher-cost purchased transportation in certain locations to manage service levels. The decrease in pounds per mile of 5.4% and 4.4% for the three and six months ended June 30, 2021, respectively, compared to the same period of 2020, was due to the higher number of miles (including purchased transportation miles) incurred to service the business growth and the increase in average length of haul resulting from intended changes in business mix, which was compensated by an increase in billed revenue per shipment.
Fuel, supplies, and expenses as a percentage of revenue for the second quarter of 2021 was consistent with the second quarter of 2020. For the six months ended June 30, 2021, fuel, supplies, and expenses as a percentage of revenue decreased 0.6 percentage points, compared to the same period of 2020. The changes in fuel, supplies, and expenses as a percentage of revenue were influenced by the effect of higher revenues including fuel surcharges, as a portion of operating costs are fixed in nature and decrease as a percent of revenue with increases in revenue levels. Fuel, supplies, and expenses increased $19.0 million and $18.6 million for the three and six months ended June 30, 2021, respectively, compared to the same prior-year period, primarily due to higher fuel costs as the Asset-Based segment’s average fuel price per gallon (excluding taxes) increased approximately 96% and 39% during the three and six months ended June 30, 2021, respectively, compared to the same period of 2020. More miles driven as a result of the increase in business levels also contributed to the year-over-year increases in fuel, supplies, and expenses. For the six months ended June 30, 2021, fuel, supplies, and expenses was also impacted by higher expenses associated with increased business levels and weather-related service center