Author(s): Meng, Huadong; Tsao, Jacob; Zhou, Kun; Picar, Justin; Mizuno, Bradley; Zhang, Wei-Bin
This report documents a research effort to understand the current practice and issues associated with Bus Rapid Transit (BRT) planning and deployment. It reviewed the design options incorporated into existing BRT deployments across California and the nation. The project team interviewed practitioners of California Department of Transportation (Caltrans) Districts and transit agencies to understand the BRT project approval decision-making process, the impacts of BRT implementation and the Measures of Effectiveness (MOEs) for transit and non-transit system performance. The studies revealed that though Caltrans and transit agencies do use a similar set of MOEs for the evaluation of BRT projects, the emphasis and parametric assumptions for the MOEs may be different and can influence the results of the evaluation. Other evaluation criteria and factors must be considered. This study concluded that a systematic approach needs to be developed and taken in the BRT planning process.
Traffic congestion and trucking activities in the San Francisco Bay Area are increasing due to the rapid population growth and economic expansion. It is imperative to explore transportation alternatives, and the Bay Area Rapid Transit (BART) system, with 63 percent unused capacity on average in non-peak hours, presents such an opportunity. If BART’s service is extended to include air-freight movement, extra revenue can be generated, truck miles travelled on highways will be reduced (potentially leading to a reduced traffic congestion and pollution), and traffic safety could be improved. The objective of this study is to identify the number of feasible dedicated freight train that can be accommodated by BART lines using its current operational schedule, without creating a negative effect on passenger service. The measurement of time or distance between two successive train-runs at a station, also referred to as the ‘headway’, for selected lines have been considered to evaluate possible freight train insertions into time-space slots of current passenger services. To qualify this, the headway of the two trains needs to be greater than twice the minimum headway required (based on BART train safety requirements). Furthermore, BART trains should be subjected to the limit on acceleration/deceleration capabilities. The findings are as follows: for peak hours and commute directions, it would be impracticable to add more trains. For peak hours in non-commute directions, some capacity could exist for mixed freight cars and on empty passenger cars. For non-peak periods such as early mornings and evenings, slots for dedicated freight train insertions are available.
Representatives of the trucking industry have been surveyed to try to identify their needs and concerns related to truck platooning systems. These surveys revealed the need to provide clearer and more comprehensive descriptions of the truck platooning concepts to ensure that the respondents understand what it is and how it works. The fleet managers tended to be more receptive to truck platooning than the drivers, and even those respondents who had some prior experience driving trucks with adaptive cruise control (ACC) and forward collision warning systems were no more receptive to truck platooning than those who lacked such experience. One group of respondents received a more complete description of the truck platoon concept and their responses were significantly more positive regarding driver acceptance of the system.
This report describes activities surrounding the design, building, deployment, operation, and evaluation of an innovative corridor management (ICM) system aiming to improve mobility within the Interstate 15 (I-15) corridor in San Diego, California, by integrating the operations of the I-15 freeway with the surrounding arterials and transit systems. Systems engineering principles were applied to support the development of the demonstration ICM system and the systems engineering process was credited by the project team with having contributed significantly to the success of the project. While full system evaluations were not yet available when this report was written, the deployed I-15 ICM system had already demonstrated its ability to identify incidents and unusual congestion events, to develop traffic management strategies integrating freeway, arterial, and transit operational elements, and to implement recommended strategies either automatically or following approval by relevant system operators. The system has also demonstrated the feasibility of using a microscopic traffic simulation model in a real-time operational environment to forecast corridor operations under alternative scenarios. Simulation evaluations have further consistently shown operational benefits exceeding deployment costs.
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.
Extensive site selection has been conducted for future testing of the CRM algorithm developed in a previous project supported by the FHWA Exploratory Advanced Research (EAR) program. Two major corridors have been analyzed: I-880 in the Bay Area and SR99 in Sacramento, California. Main factors for site selection include: road geometry, traffic volume, bottleneck locations and traffic situations, traffic data quality, and availability of ramp meter facility. Two potential test sites have identified: SR99 North Bound (NB) between 47th Street and the intersection with SR50; and I-880 NB between SR237 and Auto Mall Parkway. The Performance Measurement System (PeMS) data has been used for modeling and model calibration of the two corridors in Aimsun microscopic traffic simulation. Based on the calibrated model, the CRM algorithm has been applied. Simulation has been conducted for multiple replications. Preliminary simulation results show that on average Total Travel Time (TTT) of the overall system could be reduced by 3-5%, Total Delay (TD) on the mainline could be reduced by 10-17% Total Travel Distance could be increased by 1% and Total Number of Stops could be reduced by 15-24%. The number will depend on traffic volume. The microscopic simulation results need further fine tuning and field testing at the selected site(s) in the next phase of the project.
The report describes the methodology and findings of the evaluation of adaptive signal control in a real-life corridor. The study section was a five mile section of the Pacific Coast Highway in Los Angeles with nine signalized intersections operating under adaptive control using the Los Angeles DOT ATCS (adaptive traffic control system). Optimal fixed time time-of-day plans were developed and implemented at the test site. The performance of the ATCS system and the fixed-time plans was evaluated using extensive field data on travel times and queue lengths collected through probe vehicles, Bluetooth sensors and video cameras. The findings indicate that ATCS performed better than the fixed-time plans during the time of peak direction in the arterial through traffic. All strategies had similar performance in the midday time period. A number of limitations were identified for ATCS under oversaturated conditions, including under-allocating green time to the critical approach at the bottleneck intersection, allocating more green time than necessary at intersections upstream of the bottleneck, and inappropriate setting offsets at intersections downstream of the bottleneck resulting in additional delays for traffic departing the bottleneck and creating the potential for queue spillbacks to the bottleneck itself. Possible remedial actions for these issues are discussed.
This project investigates the causes of long clearance times of major traffic incidents in California and proposes ways to reduce major incident clearance times. Major incidents are defined as those taking 30 minutes or more to clear. The research team examined regional sources or causes of incident clearance delay, identified appropriate responsive traffic incident management (TIM) tools and strategies shown to be successful in reducing incident clearance times, and provided recommendations for improving ongoing performance measurement to support continuous improvement in safe, quick incident clearance.
This project evaluates the operational and safety benefits obtained from a dynamic lane management system. The number of lanes on an SR 110 connector was reduced from two to one to reduce collisions occurring at its entrance, where a sharp curves with low visibility forces traffic to slow down to 30-mph. To alleviate long queues on SR 110 while containing the impacts on safety, a system opening the connector's shoulder lane between 15:00 and 19:00 was activated. Evaluations used PeMS data, video recordings, travel time runs, simulation results from a Paramics microscopic modeling of the corridor, and collision records from the California Department of Transportation. Unique traffic behavior along SR-110 prevented evaluations to be conducted with the TOPL (Tools for Operational Planning) macroscopic simulation models. Evaluations revealed that between 15% and 38% of vehicles traveling on the connector illegally utilize the shoulder lane at its entrance when it is closed as a result of traffic demand exceeding the entry capacity. While the non-complying behavior was assessed to significantly reduce delays along the corridor independently of the dynamic lane management system, the simulation results indicate that operational benefits are still obtained from the system. Relatively small benefits would be obtained, however, from enabling a dynamic opening and closing of the connector shoulder lane based on the observed traffic conditions. From a safety standpoint, collision records indicate that while the current system has increased the frequency of collisions at the entrance of the connector it has also resulted in a greater reduction of collisions upstream, thus yielding overall net safety benefits.
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.
This report documents a research effort to develop requirements and recommendations for establishing a Weigh-in-Motion Test Facility (WIMTF) in California. This study finds that the effectiveness of existing WIM stations needs to be improved. A WIMTF can facilitate an in-depth understanding of the characteristics of various WIM technologies, as well as the development of new methods for dynamic calibration of WIM scales in order to improve the WIM measurement accuracy, which is critical to the effectiveness and efficiency of WIM stations. To prepare for a WIMTF, several sets of requirements, including non-functional and functional requirements, interface requirements, and data requirements for the WIMTF were developed. Potential sites for the WIMTF were evaluated. Based on the requirements, a site recommendation was made. The study also evaluated the benefits and costs of a WIMTF, concluding that the benefits will far outweigh the costs of a WIMTF.
This project evaluates existing weaving analysis procedures to determine under which design and operating conditions the “best available” tools are most effective. It also develops an improved procedure by modification of existing approaches or a new method, as appropriate. The Highway Capacity Manual 2000, Leisch and Level D methods were selected for evaluation. Analysis of results identified the strengths and limitations of each method in predicting the performance of a freeway weaving section for a range of operating conditions. Additional analyses were performed by applying the selected analysis methods to synthetic datasets for the design and operating conditions for which field data were not available. Analysis of results focused on the consistency of the predictions from each analysis method. Additional field data were collected at three California ramp weave sites. A performance matrix was developed for each weaving analysis method to serve as a guide for choosing the “best” analysis method for the weaving section under study. Each cell of the matrix represents a distinct design and operating condition. There are a total of 144 cells for typical weaving sections of two, three, four and five lanes wide. Based on the comparison of the model prediction with field and synthetic data, the authors show on each cell the performance of the particular method as good, partially good or often inconsistent, or poor for a particular design and operating condition.
Traffic data is used to estimate current traffic conditions so that travelers and agencies can make better decisions about how to use and manage the transportation network. This research explores the fusion of probe data (vehicle speed and direction) with loop data (density, speed, and count) in the context of producing overall network speed and travel time estimates. Speed and travel time estimates are useful in many circumstances, but current system control strategies (ramp metering, for example) require density data. While it is difficult to significantly increase the quantity of loop detectors on state highways, the penetration rate of probe data is continually increasing. Multiple data sources with various characteristics were fused by running probe and loop data through the Mobile Millennium highway model, generating velocity maps and travel times. The performance of data sources both individually and when fused was evaluated. It was found that the highest quality estimates are achieved by combining probe data and loop detector data.
This report describes the development of an automated speed enforcement (aSE) system. The main function of the aSE system is to communicate relevant speed, violation, and hazard information to the stakeholders in the work zone context: drivers, CHP officers, and workers. The system consists of two sub-systems that can work jointly in an integrated manner as a whole but they can also be deployed and tested separately.
Advanced signal control strategies, based on real-time information on vehicles’ location, speed and characteristics as well as communication to the signal control infrastructure, can enhance mobility, safety, and the environment. Several performance measures are proposed for evaluating signal control algorithms, and procedures for estimating the performance measures from connected vehicle data are developed using statistical techniques and kinematic wave theory. A number of control strategies are developed and tested through simulation to improve mobility: queue spillback avoidance, control for congested networks, and dynamic lane allocation. Results indicate that the proposed strategies improve traffic performance. Strategies for improving intersection safety with emphasis on avoidance of red light running (RLR) related collisions are also developed. A prototype in-vehicle driver speed advisory system for minimum fuel consumption and emissions is developed and field tests show significant fuel savings.
This research investigates the feasibility and the business case for purchasing third‐party probe data and fusing it with Caltrans’ existing data for the purpose of estimating travel times. The intent was to demonstrate an efficient and cost-effective use of alternative traffic data sources to complement the detection systems currently installed and operated by Caltrans.
This report documents the development of the Intermodal Airport Ground Access Planning Tool (IAPT), part of a combined quantitative and qualitative approach for planning for improved intermodal connectivity at California airports. The objective of developing the IAPT is to provide a standard, transparent and scientific way for quantitative airport ground access project evaluation at the airport level. In this phase, researchers improved the IAPT functionality, estimated updated versions of mode choice models, corrected errors in the calculation of performance parameters, and conducted a case study. A user-friendly graphical interface makes it easy for a user to run the model. The current version of the IAPT allows user to define multiple airports and sets of projects for each airport, and to compare the performance of these projects across airports, as well as generate regional totals of the measures of performance for different project scenarios at each airport. Local and state planning agencies can use the tool to support the analysis of airport ground access impacts and traffic flows as part of regional airport system planning.
This project examined the safety and demand issues for pedestrians and bicyclists at multi-lane roundabouts. This document presents research findings, synthesizes current information on best practices, and makes recommendations to assist local agencies planning and designing safer multi-lane roundabouts to better and more safely address the needs of bicyclists and pedestrians. The current literature is referred to throughout the document to augment the research team’s findings, especially for issues that were beyond the scope of this project. Key findings in the areas of pedestrian and bicyclist avoidance of, behavior around, and collisions at multi-lane roundabouts are presented along with recommendations for geometric design, design speed, sight distance, width of lanes, signage and pavement markings, and operational recommendations.
Research shows that drivers can reduce fuel consumption by 12% by using Signal Phase and Timing (SPaT) information. These results are based on simulations and the main goal of this project is to build a prototype system that shows that it is possible to reduce fuel consumption when a vehicle is facing multiple traffic signals in a row. An in-vehicle system computes a speed recommendation based on current SPaT information and provides it to the driver via a graphical interface. The driver should be able to adjust his/her driving speed, resulting in improved fuel consumption. In the first field test, the position data of the vehicle is sent to a second system called Adaptive Priority for Individual Vehicle (APIV). APIV is an operational strategy that adapts signal timing to facilitate the movement of individual vehicles through signalized intersections. While the main focus of the speed recommendation system is on reducing fuel consumption, the prime focus of APIV is on reducing the number of stops at red lights at intersections and reduce fuel consumption. In addition APIV helps in reducing the number of stops at red lights and associated intersection delays, reducing travel time. Comprehensive field tests using a BMW vehicle showed that significant fuel savings are possible using the APIV.
