Meta-Analysis of Adaptive Cruise Control Applications: Operational and Environmental Benefits

2019Final ReportDopart, KevinPDFTech ReportFHWA-JPO-18-743DOT-VNTSC-OSTR-19-02Inter-Agency Agreement DTFH61-15-V-00022HW9EA4Autonomous intelligent cruise controlCruise controlAutomationEmissions reductionMeta-analysisCooperativeadaptiveACCCACCV2VV2Itime gapcapacity improvementsfuel savingsUnited StatesUnited States. Department of Transportation. Intelligent Transportation Systems Joint Program OfficeEilbert, AndrewBerg, IanSmith, Scott B.John A. Volpe National Transportation Systems Center (U.S.)United States. Department of Transportation. Intelligent Transportation Systems Joint Program OfficeIntelligent Transportation Systems Joint Program Office;Volpe National Transportation Systems Center, Technical Reference CenterWith the increasing adoption of adaptive cruise control (ACC) and development of cooperative adaptive cruise control (CACC), their effect on traffic, energy, and emissions is an ever more urgent question. Using the rapidly growing body of research on these impacts, this report presents a systematic review and meta-analysis of 67 recent studies. The majority were simulation studies with a few field tests. While the assumptions and methodology between studies in our review differ widely, a meta-analysis of maximum reported capacity improvements and fuel savings confirmed that CACC applications tend to increase capacity and fuel savings over manual driving due to shortened following time gaps and greater string stability from connectivity. In contrast, ACC applications do not always show capacity improvements, and if so, these improvements are more modest on average than for CACC systems. We found that ACC systems do, however, appear to smooth driving through less braking and reduced hard acceleration events such that fuel consumption is reduced, but not on average as much as CACC systems.81