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Open Access Publications from the University of California

Scholarly Works (20 results)

  • Article
Research Reports (2008)

Currently, Federal and State governments are partnering with private industries and academia institutions to pursue the deployment of intersection decision support (IDS) and cooperative intersection collision avoidance systems (CICAS), which seek to combine infrastructure-based and vehicle-based functions to provide optimal solutions for roadway users. The overall (IDS) research plan was constructed to explore the requirements, tradeoffs assessment, and technology investigations necessary to define a Cooperative Intersection Collision Avoidance System. This report is the third report on the California PATH IDS research, and it focuses on two human factors studies which used the PATH instrumented Ford Taurus research vehicle to study driver behavior while making left turns.

The goal of the first study was to observe drivers? intersection approaches and left-turn maneuvers in a mostly naturalistic setting. Twenty-three drivers (both male and female and younger and older) were recruited to drive the instrumented vehicle 10 times around an 8-block course in the city of Berkeley, CA, making a total of 40 left turns per driver. The instrumented vehicle recorded driver actions, such as approach speed, brake activation, steering inputs, and limited estimates of oncoming vehicle gap (and lag) acceptance.

The goal of the second study at the California PATH Richmond Field Station (RFS) instrumented intersection was twofold. First, left-turn gap (or lag) acceptance was examined in an environment where gaps could be more accurately measured and tightly controlled. Second, the study introduced drivers to the concept of a left-turn Driver Infrastructure Interface (DII), a dynamic, no-left-turn sign, warning sign. Twenty drivers (both male and female and younger and older) were recruited to drive the instrumented vehicle through the RFS intersection 54 times with a single oncoming vehicle approaching. The vehicle approaches were timed to test the effects of different DII settings such as warning threshold onset timing on gap (lag) acceptance.

    Cover page: California Intersection Decision Support: A Driver-Centered Approach to Left-Turn Collision Avoidance System Design
    • Article
    Research Reports (2008)
    Each year in the United States over 450,000 large trucks are involved in crashes, resulting in about 5000 fatalities and 120,000 injuries. Significantly, truck driver error is a major causal factor to truck-involved crashes. This points toward onboard monitoring as a promising means to encourage good driving behavior, it would recognizing and provide necessary feedback to correct self-induced hazardous driving situations. This is the basis for our past prototype development effort, which has produced under Task Orders 5509 and 6609 a suite of hardware on a Freightliner Century Class.This suite allows for online measurement of a set of driving characteristics which are indicators of unsafe driving behavior, with feedback given in real time to the driver, and offline to the carrier (and ultimately, back to the driver). Under this Task Order, we extended our work to detail a Field Operational Test. While that FOT began with 15 trucks, the work undertaken was expanded at US DOT’s request to consider additional teammates and a scope of over 200 trucks where the FOT could be collateral compared to the naturalistic data collection that could be accrued. We describe the original SOW, some of the transforming work in-between, then the finally-conceived FOT which in the end was submitted but not awarded to the PATH-Caltrans team.
      Cover page: Onboard Monitoring and Reporting for Commercial Vehicle Safety (OBMS) Phase II: Field Operational Test
      • Article
      Research Reports (2014)
      This research identifies the operational concepts for managing cooperative adaptive cruise control (CACC) vehicle maneuvering and traffic flows. This includes approaches for grouping the CACC vehicles, ranging from ad-hoc to centrally coordinated strategies, and the incentives that could be used to facilitate the vehicle clustering, both operational and financial. These are particularly important at low market penetrations, when the CACC vehicles are likely to be widely separated. The dissolution of CACC strings is also discussed, since this needs to be done carefully to avoid adverse traffic impacts. While the main focus is on vehicle-to-vehicle (V2V) CACC for use on limited access highways, strategies for infrastructure to vehicle (I2V) CACC and for both V2V and I2V CACC on signalized arterials are also considered. Connected Cruise Control (CCC), which has been developed as a driver-advisory transitional strategy to lead toward CACC in the Netherlands, is also discussed.
        Cover page: Using Cooperative Adaptive Cruise Control (CACC) to Form High-Performance Vehicle Streams
        • Article
        Research Reports (2011)
        The work reported here includes the development of the underlying theory for detecting traffic flow breakdown at a bottleneck and for defining the speed profiles that vehicles should be following in order to maximize the flow through the bottleneck region. It also includes a preliminary test of the communication of the variable speed limit values to an instrumented vehicle for display to drivers from the general public, in order to determine their reactions to the variable speed limits. The selection of variable speed limits (VSL) to reduce traffic breakdowns is based on careful modeling of the traffic dynamics and estimation of the probability of breakdown as a function of traffic speed and density. The VSL values chosen by the algorithm developed here were broadcast to a test vehicle driven along the I-80 corridor by 16 drivers from the general public, and their reactions to the VSL information were captured by recording data about their driving behavior and collecting their responses to a questionnaire. These results indicated that although the VSL concept is very promising, the implementation needs to provide for better filtering of noisy and inconsistent data so that drivers receive a display of VSL values that are stable in location and time and appear believable to the drivers.
          Cover page: Freeway Traffic Control Using Variable Speed Limits
          • Article
          Research Reports (2011)
          This project has shown how connected vehicle systems, based on vehicle-vehicle and vehicle-infrastructure communication and coordination, can support the development of mobility-enhancing applications with the potential to transform the performance of the road transportation system. Three separate mobility-enhancing applications were developed, simulated, and tested, and their expected mobility benefits were estimated using simulations. Cooperative adaptive cruise control was shown to have a high potential for user acceptance, and when applied at the gap settings chosen by representative drivers from the general public, it could double the capacity of a highway lane at full market penetration. Variable speed limits were shown to have the potential to reduce the adverse impacts of highway bottlenecks by increasing the traffic flow capacity of those bottlenecks if they can be implemented with smooth transitions in the speed limit settings. Automated truck platoon control was shown to be technically feasible using DSRC for vehicle-vehicle coordination, with the potential for significant fuel savings from aerodynamic drag reductions.
            Cover page: Development and Assessment of Selected Mobility Applications for VII: Principal Findings
            • Article
            Research Reports (2018)
            Cooperative Adaptive Cruise Control (CACC) is a term that has been used rather loosely in recent years, such that different people visualize different functions and capabilities when discussing CACC systems. Thus, there are now multiple system concepts that have been described under the CACC label, and the functionalities included in these varied concepts can be quite different from each other. At the heart of each CACC concept is the merging of Adaptive Cruise Control (ACC), a subset of the broader class of automated speed control systems, with acooperative element, such a Vehicle-to-Vehicle (V2V) or Infrastructure-to-Vehicle (I2V) communication. The V2V communication could provide information about the vehicle or vehicles directly in front of you, and the I2V communication could provide information about traffic further ahead or about current speed restrictions as part of an active traffic management approach.There are two primary transportation system motivations for the development of CACC. The first motivation is to reduce traffic congestion and the second is to improve fuel efficiency. It may also improve safety, although it is not primarily a safety system. At the individual driver level, CACC can make ACC more attractive and convenient to drivers by providing behavior that is more responsive to preceding vehicle speed changes, that gives an enhanced sense of safety because of its quicker response, and that deters cut-ins at shorter gaps.
              Cover page: Using Cooperative Adaptive Cruise Control (CACC)to Form High-Performance Vehicle Streams. Definitions, Literature Review and Operational Concept Alternatives
              • Article
              Research Reports (2012)
              The Mobile Millennium project provided a platform for aggregating traffic information across various sources, including infrastructure sensors, commercial data feeds, probe vehicles, and probe cell phones. The Networked Traveler project provided the California PATH instrumented research vehicle platform used to both deliver vehicle probe data back to the infrastructure and to generate Advanced Driver Assistance Systems (ADAS) alerts to the drivers of those vehicles. The main theme of this collaboration project was to demonstrate the potential to create Enhanced Probe Vehicles (EPVs) by merging vehicle CAN-bus data with the typical GPS data that is provided by normal probe vehicles. The first goal of this project was integrate the two systems, allowing the instrumented research vehicles to communicate with the Mobile Millennium traffic aggregation servers. The second goal was to enhance the data gathered and stored by the Mobile Millennium traffic aggregation server to include the enhanced information provided by the EPVs, specifically, to include hazard warning light activation events. The third and final goal of this project was to integrate the information provided by the EPVs to the traffic server into soft-safety alerts that could be provided to the drivers of the EPVs and demonstrate the prototype system. This report documents the systems that were built for the demonstration, and provides a short analysis of the system performance from data gathered through both a simulation and an on-the-road vehicle test
                Cover page: Providing In-Vehicle Soft Safety Alerts Using Mobile Millennium Data and Vehicle Event Information
                • Article
                Research Reports (2015)
                Cooperative Adaptive Cruise Control (CACC) provides an intermediate step toward a longer-term vision of trucks operating in closely-coupled automated platoons. There are important distinctions between CACC and automated truck platooning. First, with CACC, only truck speed control will be automated, using vehicle to vehicle (V2V) communication to supplement forward sensors. The drivers will still be responsible for actively steering the vehicle, lane keeping, and monitoring roadway and traffic conditions. Second, while truck platooning systems have relied on a Constant Distance Gap (CDG) control strategy, CACC has relied on a Constant-Time Gap (CTG) control strategy, where the distance between vehicles is proportional to the speed. For these reasons, a series of trucks using CACC is referred to as a string, rather than a platoon. This report mainly focuses on describing the various CACC operational concept alternatives at the level of individual vehicles, local groups of vehicles and their drivers, and which alternatives should be employed in this research project. These operational concepts can be broken into four categories: string formation, steady-state cruising, string split maneuvers, and faults or abnormal operating conditions.
                  Cover page: Cooperative Adaptive Cruise Control (CACC) for Truck Platooning: Operational Concept Alternatives
                  • Article
                  Research Reports (2018)
                  Cooperative Adaptive Cruise Control (CACC) provides an intermediate step toward a longer-term vision of trucks operating in closely-coupled automated platoons on both long-haul and short-haul freight corridors. There are important distinctions between CACC and automated truck platooning. First, with CACC, only truck speed control will be automated, using V2V communication to supplement forward sensors. The drivers will still be responsible for actively steering the vehicle, lane keeping, and monitoring roadway and traffic conditions. Second, while truck platooning systems have relied on a Constant Distance Gap (CDG) control strategy, CACC has relied on a Constant-Time Gap (CTG) control strategy, where the distance between vehicles is proportional to the speed.
                    Cover page: Cooperative Adaptive Cruise Control (CACC) For Partially Automated Truck Platooning:Final Report
                    • Article
                    Research Reports (2011)
                    This report describes the SafeTrip-21, Networked Traveler Foresighted Driving Field Experiment conducted as part of the US DOT’s SafeTrip-21 initiative. This experiment developed and evaluated an Advanced Driver Assistance System providing soft-safety or situational awareness alerts regarding “Slow Traffic Ahead” when driving on a freeway. The Networked Traveler system detects slow traffic or queues at several thousand locations in the Bay area, monitors the locations and speeds of its test subjects as they drive, and determines if the driver is approaching the slow traffic fast enough to warrant an alert. If so, the system alerts the driver through an auditory interface. The desired outcome is a foresighted reduction in speed, resulting in a smoother overall transition into the oncoming traffic queue. The system aims to reduce the likelihood of end-of-queue crashes on freeways, this being a subset of the class of rear-end crashes. The hypothesis is tested by computing measures representing the Root Mean Square (RMS) Error of Speed, Peak Deceleration Rate, Mean Deceleration Rate, Deceleration Due to Braking, Pre-Braking Deceleration, and Time before the start of braking. Amongst these, the RMS Error of Speed across all subjects most clearly confirms the test hypothesis -enhanced situational awareness results in smoother driving.
                      Cover page: SafeTrip 21 Initiative: Networked Traveler Foresighted Driving Field Experiment Final Report
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