Operational speed strategy opportunities for autonomous trucking on highways

Abstract

This study examines the potential for cost and carbon emission reduction for autonomous trucks to adopt lower peak speeds than today's human driven trucks, where the hourly cost of the driver remains a significant trade-off. Adopting lower speeds presents an indirect savings opportunity in addition to savings associated with the removal of the driver. Benefits and trade-offs for varying target speed of autonomous trucks on highways were investigated with a parameterised analysis of transport and cargo cost components. A validated fuel consumption model was used to compare fuel consumption for different speed strategies across idealised highway drive-cycles and vehicle scenarios. A volume-limited tractor-trailer (50% cargo mass capacity) could reduce fuel consumption and carbon emissions by 26% when reducing target speed from 90 km/h to 70 km/h. When the trade-offs of driver, vehicle and cargo time are considered for the same 20 km/h target speed reduction, combined costs increase by 3% for the human driver scenario, but decrease by 4% for an autonomous truck (assuming medium cargo time value). Sensitivity to vehicle type, loading, drive-cycle and cargo value was examined. A UK supermarket chain case study was investigated and key differences between a UK and US context were compared. Mandatory rest breaks and Hours-of-Service restrictions were identified as additional barriers for human driven vehicles to adopt slower speed strategies.