conference paper
conference paper
Autonomous Driving (AD) is a rapidly developing technology and its security issues have been studied by various recent research works. With the growing interest and investment in leveraging intelligent infrastructure support for practical AD, AD system may have new opportunities to defend against existing AD attacks. In this paper, we are the first to systematically explore such a new AD security design space leveraging emerging infrastructure-side support, which we call Infrastructure-Aided Autonomous Driving Defense (I-A2D2). We first taxonomize existing AD attacks based on infrastructure-side capabilities, and then analyze potential I-A2D2 design opportunities and requirements. We further discuss the potential design challenges for these I-A2D2 design directions to be effective in practice.
journal article preprint
Freight transportation plays a vital role in the economy of the nation and the state of California in particular. The value of total freight shipments originating in California in 1997 is estimated $638.5 billion, 10.6 percent of all US shipments by value. This represents 706.5 million tons of fright an amount equal to 7.2 percent of the freight move nationally, measured by weight. Measured by value and weight, respectively, 67.4 and 73.7 percent of this fright moved by tuck. An additional 15.4 and 2.4 percent (by value and weight) of the freight originating in California moved over more than one mode, most likely spending part of its journey over the road. The California Trucking Association estimates that trucking employs one out of twelve workers in California.
working paper
The central goal of this research is to develop a systematic framework and the support tools to ease, streamline and speed up the calibration of micro simulation projects. Part III of the final report documents the accomplishments achieved in the second phase of the research project. They include the following.
First, to overcome the lengthy time it takes for GA to obtain local and global driving behavior modeling parameters, we implemented a faster heuristic optimization technique, the simultaneous perturbation stochastic approximation (SPSA) and compared its performance with other heuristic optimization methods. Results indicate that SPSA can achieve comparable calibration accuracy with much less computational time than the often used Genetic Algorithm (GA) method.
Second, we developed a much faster O-D estimation tool to obtain an initial time-dependent O-D trip table. This O-D trip table can be used as a seed table in Paramics’ own O-D estimator for further refinement, or directly used in a micro simulation. In either case, the estimation time of O-D trip tables can be considerably shortened. Since our O-D estimation tool makes use of a macroscopic traffic model (logit path flow estimator, or LPFE), a network conversion tool is therefore developed to convert Paramics’s detailed network settings to those of LPFE and vice versa.
Third, we enhanced the vehicle actuated signal control APIs in Paramics, making it more versatile to implement and simulate various types of actuated traffic control strategies found in practice. We also developed a set of guidelines to help micro simulation users to set up and check signal settings in a micro simulation project.
Finally, we developed a summary statistics tools to track, diagnose and report on the calibration as it progresses or after it terminates, and carried out a case study using the SR-41 network in Fresno to demonstrate the use of the developed tools, identify potential problems and summarizing our calibration experiences with large scale networks.
Our case study indicates that the developed calibration tools can indeed ease, streamline and speed up the calibration of micro simulation, particularly when the network concerned is large. It also reveals that the calibration of a micro simulation is a complex task that involves numerous engineering judgments and cannot be fully automated. In a micro simulation, every modeling detail matters and each must be treated properly to ensure a good simulation outcome.
MS Thesis
The growing number of people commuting and making trips by bicycle and the associated health and environmental benefits of this trend has captured the attention of transportation engineers and planners in recent years. However, a review of the current literature reveals a limited understanding of travel behavior of bicyclists, in particular bicyclists’ route choice behavior. This study investigates factors influencing bicyclists’ route choice and examines their willingness to deviate from the shortest route. Intercept surveying techniques were coupled with a self-administered web-based surveying tool to collect mapped routes of bicyclists. The data were used to (1) perform multinomial logit (MNL) model estimations and (2) evaluate deviation ratios. The MNL model estimations suggested that factors such as exposure to vehicle traffic, number of signalized intersections, and overall safety were statistically significant with coefficient signs as expected. Travel time was found to be marginally significant with a coefficient sign as expected. The deviation ratio analysis found that in general bicyclists were willing to deviate 27% (1.27); persons in the 45 to 54 years of age category had the highest deviation ratio (1.45); males and females had the same deviation ratio (1.27); “very confident” bicyclists were willing to deviate 12% farther than “fairly confident” bicyclists; persons traveling more than 9 miles tended to have a higher deviation ratio; and work-based-trips had an 18% higher deviation ratio than non-work-based trips. The combine results suggest that bicyclists are willing to deviate considerably for a safe route with low exposure to vehicle traffic and signalized intersections.
research report
This study examines whether co-locating stations for light-duty zero emission vehicles (ZEVs) with stations for heavy-duty ZEVs would increase network coverage and improve resiliency to help California achieve its targets for widespread ZEV adoption. The study separately models of siting light-and heavy-duty at the same locations vs. separate locations for (i) electric charging stations and (ii) hydrogen refueling stations. The results indicate electric charging stations in California are being used at only 13% of total capacity. Building out and optimizing the locations of light-duty electric vehicle stations will results in greater demand met and resiliency than will co-locating these at heavy-duty charging stations. On the other hand, co-location of hydrogen refueling stations for light duty vehicles at sites for heavy-duty vehicle stations may increase demand met, network resiliency, and adoption rates of light-and heavy-duty fuel cell electric vehicles. These adoption rates are constrained by the current infrastructure.
Phd Dissertation
This work joins a body of literature that tests whether commuting data support: (a) a hypothesized mismatch between employment or shopping opportunities among isolated groups of urban residents; and (b) the equitable distribution of mobility benefits following the opening of a major urban freeway. A history of the urban interstate system and the legislation guiding its construction is provided first as a background to the study. Second, a social ecological interpretation of the multi-dimensional effects of a change in urban form is introduced with a specific orientation toward freeway sitings. New highway impacts vary depending upon the condition of the surrounding area and proximity to the facility. Three grouping variables are introduced as possible means through which to categorize residents severely impacted by the construction of the Glenn M. Anderson (Century) Freeway/Transitway (Interstate 105). A behavioral measure segments residents based on the social and economic conditions in their census tracts. Two geographic grouping variables separate inner city residents from more suburban residents and residents close to the right-of-way from those more than a mile from the construction. U.S. Census data illustrate the social and economic differences among these groups within the Century Freeway corridor area. It is determined that, at an aggregate level, mean travel time to work is longer for residents of distressed areas, central city areas and residents near the right of way. Residents in the study area are surveyed at two points in time. Baseline travel behavior analyses indicate that controlling for race, education, income, and mode choice, the work trip of South Central Los Angeles residents is longer than neighboring areas in the corridor. Also, this trip is longer for residents living within one mile of the freeway. The behavioral variable does not aid in the discrimination of work trip travel times. Analysis of transportation behavior subsequent to the freeway opening reveals that the travel time savings for work and nonwork trips are unequally distributed across the study area. Significantly, the freeway opening is not associated with a convergence of work trip travel times. Those least affected by highway construction demonstrate travel benefits that are not found among severely impacted respondents.
Phd Dissertation |
Jun 1993
Phd Dissertation |
Jun 1995
Phd Dissertation |
Jun 1996
working paper
This paper reports the results of an effort directed toward developing a consistent methodology to assess the impacts of traffic disruption due to major transportation reconstruction/rehabilitation projects during the period of implementation. In the approach taken by this research, state-of-the-art traffic simulation models are used to estimate the performance of the transportation system during various construction phases. Alternative construction and traffic redirection strategies designed to minimize both the direct and indirect losses associated with the construction/rehabilitation are then evaluated with the development of a systematic, computerized procedure designed to: 1. provide for the creation and comparison of multiple and ‘layered’ reconstruction/rehabilitation scenarios,2. minimize the required knowledge of both the detailed interactions with the model as well as the host computer, and 3. produce meaningful, comparative outputs that assist in the selection of reasonable alternatives. The resulting modeling environment is viewed as a convenient tool to assist both the traffic engineer and the transportation planner in selection of reasonable reconstruction/rehabilitation plans and schedules.
conference paper
published journal article
