conference paper
Dynamic analyses of complex travel behavior using a sample of the Dutch National Mobility Panel
Proceedings, Round Table Conference on the Analysis of Panel Data
Publication Date
January 1, 1987
Area of Expertise: Unspecified
published journal article
Bus rapid transit systems: A comparative assessment
Transportation
Publication Date
March 1, 2008
Author(s)
David A. Hensher, Thomas Golob
Abstract
Bus rapid transit (BRT) is a system operating on its own right-of-way, either as a full BRT with high quality interchanges, integrated smart card fare payment and efficient throughput of passengers alighting and boarding at bus stations; or as a system with some amount of dedicated right-of-way (light BRT) and lesser integration of service and fares. This paper evaluates the status of 44 BRT systems in operation throughout the world in order to identify BRT’s capability of moving substantial numbers of passengers, using infrastructure whose costs overall and per kilometer are low. The cost of constructing the BRT infrastructure and the range of design and service specifications offered through BRT are examined. The findings indicate that most of the systems, with all manner of variation and in both developed and developing nations, cost less than $10 million per kilometer. Substantial variations in total costs can be attributed in part to data limitations and the context in which costs were negotiated.
Suggested Citation
David A. Hensher and Thomas F. Golob (2008) “Bus rapid transit systems: A comparative assessment”, Transportation, 35(4), pp. 501–518. Available at: 10.1007/s11116-008-9163-y. conference paper
Heuristics for freight procurement auctions with carrier capacity and shipper side constraints
Proceedings of the 88th annual meeting of the transportation research board
Publication Date
January 1, 2009
Author(s)
Abstract
Combinatorial auctions, in which trucking companies bid on contracts for bundles of lanes, rather than single ones, hold significant promise for adding efficiencies to contracts for freight transportation services. However, the problems faced by bidders (trucking companies) and auctioneers (large shippers) in order to effectively bid and select contract winners are very computationally complex â?? preventing widespread adoption of such auctions to date. In this research the authors provide heuristics for solving combinatorial auctions for freight procurement and demonstrate that complicated side constraints (favoring incumbents, creating backup assignments, and minimizing the number of winning carriers) can be considered â?? benefiting both shippers and carriers. The authors do this in a setting where carriers can bid on as many lanes or packages as they wish and in which shippers explicitly consider carrier capacities when assigning contracts. Empirical analysis shows that othe authors heuristics, based on the LP rounding technique developed by Shmoys and Tardos for the generalized assignment problem have very good performance.
Suggested Citation
Matthew Nguyen, Sandy Irani and Amelia Regan (2009) “Heuristics for freight procurement auctions with carrier capacity and shipper side constraints”, in Proceedings of the 88th annual meeting of the transportation research board, p. 34p. published journal article
Parsing density changes: An outcome-oriented growth management policy analysis
J Hous and the Built Environ
Publication Date
November 1, 2012
Author(s)
Jae Hong Kim, Brian Deal, Arnab Chakraborty
Abstract
Although a considerable number of studies have examined the effectiveness of growth management programs in curbing sprawl and increasing aggregate densities, less attention has been paid to understanding how these noted density improvements are realized. In this paper, we assess the mechanisms that underlie changes in aggregate population densities and empirically examine detailed density changes under various growth management regimes in the US. Our county-level statistical analysis using recent US Census products and land use change data sets, finds that: (a) states with proactive growth management programs do tend to experience relative density gains, but not in jurisdictions with restrictive local land use regulations and (b) the marginal density gains appear to be attributable in large part to smaller housing vacancy rates and housing price escalations. Not surprisingly, our findings suggest that local structures are critical for achieving desired outcomes. Given the critical role of local action, the realization of compact development requires a tightly woven and integrated policy that not only makes logical sense at state levels, but can be followed and implemented at the local level.
Suggested Citation
Jae Hong Kim, Brian Deal and Arnab Chakraborty (2012) “Parsing density changes: An outcome-oriented growth management policy analysis”, J Hous and the Built Environ, 28(3), pp. 529–546. Available at: 10.1007/s10901-012-9327-0. published journal article
Bayesian mixture model for estimating freeway travel time distributions from small probe samples from multiple days
Transportation Research Record
Publication Date
January 1, 2009
Author(s)
Abstract
This study formulates a hierarchical Bayesian mixture model for estimating travel time distributions along freeway sections by using small data samples from vehicle probes, which have been collected over multiple days. Two normal components are used to capture the heterogeneity in the experienced travel times and to model various distributional shapes generally known to be skewed or multimodal. Travel time data collected during different intervals under similar traffic conditions are used to construct the prior for model parameters via a hierarchical Bayesian formulation. The posterior distributions can be continuously updated as new data from probes become available, and are used for prediction under different levels of data availability. A simulation study shows that true travel time distribution for each section during each interval can be well-approximated with the use of this proposed model.
Suggested Citation
Klayut Jintanakul, Lianyu Chu and R. Jayakrishnan (2009) “Bayesian mixture model for estimating freeway travel time distributions from small probe samples from multiple days”, Transportation Research Record, 2136(1), pp. 37–44. Available at: 10.3141/2136-05. conference paper
Private Autonomous Vehicles and Their Impacts on Last-mile Travel: Integrated Mode Choice and Parking Assignment Model
101st Annual Meeting of the Transportation Research Board
Publication Date
January 1, 2022
Author(s)
Suggested Citation
Younghun Bahk, Michael Hyland and Sunghi An (2022) “Private Autonomous Vehicles and Their Impacts on Last-mile Travel: Integrated Mode Choice and Parking Assignment Model”. 101st Annual Meeting of the Transportation Research Board. conference paper
Evaluating the impacts of start-up and clearance behaviors in a signalized network: A network fundamental diagram approach
Proceedings of the 98th annual meeting of the transportation research board
Publication Date
January 1, 2019
Author(s)
Abstract
Numerical simulations have shown that the network fundamental diagram (NFD) of a signalized network is significantly affected by the green ratio, and an analytical approximation of the NFD has been derived from the link transmission model.However, the consistency between these approaches has not been established, and the impacts of other factors are still unrevealed. In this paper, the authors evaluate the impacts of start-up and clearance behaviors in a signalized network from a network fundamental diagram approach. Microscopic simulations based on Newellâ??s car-following model are used for testing the bounded acceleration (start-up) and aggressiveness (clearance) effects on the shape of the NFD in a signalized ring road.This new approach is shown to be consistent with theoretical results from the link transmission model, when the acceleration is unbounded and vehicles have the most aggressive clearance behaviors. This consistency validates both approaches; but the link transmission model cannot be easily extended to incorporate more realistic start-up or clearance behaviors. With the new approach, the authors demonstrate that both bounded acceleration and different aggressiveness lead to distinct network capacities and fundamental diagrams. In particular, they lead to start-up and clearance lost times of several seconds; and these lost times are additive. Therefore, the important role that these behaviors play in the NFD shape is studied to reach a better understanding of how the NFD responds to changes. This will help the authors to design better start-up and clearance behaviors for connected and autonomous vehicles
Suggested Citation
Adria Morales Fresquet and Wenlong Jin (2019) “Evaluating the impacts of start-up and clearance behaviors in a signalized network: A network fundamental diagram approach”, in Proceedings of the 98th annual meeting of the transportation research board, p. 20p. research report
Energy commission models for analyzing and projecting household transportation energy demand: Evaluation, model improvement options, and recommendations
Publication Date
January 1, 2016
Author(s)
David Bunch, David Brownstone
Suggested Citation
David S. Bunch and David Brownstone (2016) Energy commission models for analyzing and projecting household transportation energy demand: Evaluation, model improvement options, and recommendations. University of California, Davis and University of California, Irvine. published journal article
Editorial objectives - decision-analysis
MANAGEMENT SCIENCE
Publication Date
January 1, 1995
Author(s)
Rt Clemen, Lr Keller
Suggested Citation
Rt Clemen and Lr Keller (1995) “Editorial objectives - decision-analysis”, MANAGEMENT SCIENCE, 41(5), p. U3. Phd Dissertation
Novel Vulnerability Discoveries, Measurements, and Attack Designs for Safety-Critical Autonomous Systems from Practicality Perspectives
Publication Date
January 1, 2024
Author(s)
Abstract
Autonomous systems, such as autonomous driving (AD), rely heavily on real-time perception systems to detect and interpret their surroundings, such as traffic cones, pedestrians, traffic signs, vehicles, etc. These perception systems predominantly employ Deep Neural Networks (DNNs) for tasks such as real-time object detection due to their superior performance. However, DNNs are inherently vulnerable to adversarial attacks—maliciously crafted inputs designed to cause the DNNs to malfunction. Given the safety- and mission-critical nature of autonomous systems, it is crucial to systematically investigate the potential security vulnerabilities of these systems in real-world settings. So far, one of the most general yet crucial limitations for prior research works in this area is their limited practicality in real-world autonomous system setups, either due to their sole focus on the AI component alone, which makes it non-trivial to transfer their component-only attack effects to the system level, or due to their research scopes limited to academic prototypes instead of real-world systems. For example, almost all prior adversarial attacks on Traffic Sign Recognition (TSR) systems have only assessed the effects on academic TSR models, leaving the impacts on real-world commercial TSR systems largely unexplored. While a few recent works have attempted to evaluate the impact on commercial TSR systems, these efforts are typically confined to a single vehicle model, sometimes even an unidentified one, raising questions about both the generalizability and representativeness of their findings. In this dissertation, I present a suite of research efforts toward novel vulnerability discoveries, measurements, and attack designs for safety-critical autonomous systems from practicality perspectives. By systematically discovering and understanding the security vulnerabilities at both the DNN model level and autonomous system level, these research efforts aim to provide new and useful insights that can inspire further exploration of this largely under-explored aspect in this research area.