Meta-Analysis and Systematic Review on Cooperative Adaptive Cruise Control in the USA Evaluates Its Operational Performance and Environmental Impacts.
Adaptive Cruise Control (ACC) is an advanced driver-assistance system that automatically adjusts a vehicle’s speed to maintain a safe following distance from the vehicle ahead while Cooperative Adaptive Cruise Control (CACC) elevates this technique by allowing vehicles to communicate with each other, both ACC and CACC aimed to reduce traffic congestion, optimize highway capacity and enhance road safety. This study conducted a systematic review and meta-analysis of 67 recent ACC and CACC studies as of 2018, focusing on their operational performance and environmental impacts, majority being simulation studies with a few field tests. Most of the included studies were published in 2016 or later.
In this study, the systematic review was conducted based on the following selection criteria: i) either ACC or CACC technologies or both, ii) both simulations and field tests, iii) network- and corridor-level applications on freeways, iv) quantifiable impacts to vehicle operations, fuel use, and emissions, and
v) studies of passenger vehicles (a few heavy-duty vehicle studies were also included for reference). The research team also conducted a meta-analysis, taking into account both qualitative and quantitative data related to ACC and CACC's operational performance and environmental impacts.
- The results from the researchers’ meta-analyses of maximum reported roadway capacity improvements and fuel savings confirmed that CACC applications tend to increase capacity and fuel savings over manual driving. The CACC studies showed an increase in capacity (or observed throughput) ranging from three to 100 percent, with an average of 59 percent.
- Capacity changes ranged from -26 to 66 percent for ACC driving, with an average of seven percent. On the other hand, ACC systems did, however, appear to smooth driving through less braking and reduced hard acceleration.
- The studies of ACC or CACC applications showed fuel savings in the range of two to 47 percent, though impacts between systems were mostly indiscernible with an average savings of ten percent for ACC and 11 percent for CACC.