University of Twente Student Theses


Automating the drivers' behaviour : the use of Cooperative/Adaptive Cruise Control

Nienhuis, J.H. (2009) Automating the drivers' behaviour : the use of Cooperative/Adaptive Cruise Control.

Abstract:This report is the result of three months of research conducted at the Partners for Advanced Transit and Highways (PATH) Program of UC Berkeley. The goal was "to find relations between the usage of Adaptive Cruise Control (ACC) and Cooperative Adaptive Cruise Control (CACC) and traffic conditions.” ACC is an advanced version of cruise control; next to a fixed speed, ACC can also set a fixed gap to the preceding vehicle. With this enhancement, the user does not have to shut down the system or change lanes when he encounters slower moving vehicles. CACC gets a wireless feed of information from the preceding vehicle, unlike ACC, which measures distances with radar. Shorter gaps can be accomplished using CACC. Can you estimate ACC and CACC usage levels by looking at traffic conditions? Are there patterns in the systems' usage with regard to changes in traffic conditions? How do drivers use the available gap settings presented to them? Is there a noticeable difference in the drivers' usage of ACC and CACC? With answers to these questions, the impact future C/ACC systems have on the highway throughput can be better estimated. Knowing the drivers' C/ACC usage also enables better product development. Traffic data needed for this research comes from the highway Performance Measurement System, PeMS, which gathers occupancy, flow and speed measurements from loop detectors throughout California. Furthermore, test subjects drove a vehicle that collects ACC and CACC usage data. These two sources are combined in a new database used to answer the research questions. There is a clear pattern in the relationship between C/ACC usage and traffic speed. These two variables are related linearly, with usage levels around 20% in slow moving traffic (~10 m/s) to 80% or more when traffic is freely flowing (~30 m/s). When drivers have to decelerate from 35 m/s to 20 m/s, 80% of the users who had the system on in the first case, shut it down between 20 m/s and 25 m/s. This is a breakpoint for C/ACC usage when it comes to traffic conditions. Participants state that comfort is a major argument for deciding to deactivate the C/ACC system. Furthermore, there is not a clear relationship between gap setting and traffic conditions. Drivers base their gap settings primarily on their own, rarely fluctuating, preferences. In 85% of the C/ACC active periods, the drivers did not change their gap. It can therefore be hypothesized that drivers choose what they like when turning the system on, and turn the system off when they are not comfortable with this initial choice. In addition, baseline drives, without C/ACC usage, show that drivers choose longer gaps in light traffic when compared to CACC and shorter gaps in dense traffic when compared to ACC. Therefore, since drivers turn off their C/ACC in dense traffic, they must be more comfortable with manual driving. Following this line of thinking, gaps that dynamically/automatically change according to traffic conditions should increase the C/ACC active percentage in dense traffic.
Item Type:Essay (Bachelor)
Faculty:ET: Engineering Technology
Subject:56 civil engineering
Programme:Civil Engineering BSc (56952)
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