2015 - USA - Effect of Roughness on Vehicle Operating Costs

This paper presents a summary of findings on the effect of pavement roughness [international roughness index (IRI)] and texture [mean profile depth (MPD)] on vehicle operating costs. The most important cost affected by roughness was fuel consumption, followed by repair and maintenance, then tire wear. An increase in IRI of 1 m/km (63.4 in./mi) increased fuel consumption of passenger cars by 2% to 3%, regardless of speed. For heavy trucks, this increase was 1% to 2% at 70 mph and 2% to 3% at 35 mph. Surface texture and pavement type had no effect on fuel consumption for vehicle classes except heavy trucks. An increase in MPD of 1 mm (0.039 in.) increased fuel consumption by 1.5% at 55 mph and 2% at 35 mph. The effect of pavement type on fuel consumption was statistically not significant for all light vehicles and was statistically significant for heavy trucks only at 35 mph in summer conditions (308C). No data were available for heavy trucks in winter. For repair and maintenance, there was no effect of roughness up to an IRI of 3 m/km (190 in./mi). Beyond this range, an increase in IRI up to 4 m/km (254 in./mi) increased repair and maintenance costs by 10% for passenger cars and heavy trucks. At an IRI of 5 m/km (317 in./mi), the increase was up to 40% for passenger cars and 50% for heavy trucks. An increase in IRI of 1 m/km (63.4 in./ mi) increased tire wear of passenger cars and heavy trucks by 1% at 55 mph.