Kaan Ozbay

Overall impacts of off-hour delivery programs in New York city metropolitan area

This paper examines the chief findings of research conducted on policies to foster off-hour deliveries (OHDs) in the New York City metropolitan area. The goal was to estimate the overall impacts of eventual full implementation of an OHD program. As part of the research, a system of incentives was designed for the receivers of deliveries the system combined Global Positioning System (GPS) remote sensing monitoring with GPS-enabled smart phones to induce a shift of deliveries to the off-hours from 7:00 p.m. to 6:00 a.m. The concept was pilot tested in Manhattan by 33 companies that switched delivery operations to the off-hours for a period of 1 month. At the in-depth interviews conducted after the test, the participants reported being very satisfied with the experience. As an alternative to road pricing schemes that target freight carriers, this was the first real-life trial of the use of financial incentives to delivery receivers. The analyses indicate that the economic benefits of a full implementation of the OHD program are in the range of

Derivation and Validation of New Simulation-Based Surrogate Safety Measure

147 to

Modeling traffic flow interrupted by incidents

193 million per year, corresponding to savings on travel time and environmental pollution for regular-hour traffic as well as productivity increases for the freight industry. The pilot test also highlighted the great potential of unassisted OHD—that is, OHD made without personnel from the receiving establishment present—because almost all participants who used this modality decided to continue receiving OHD even after the financial incentive ended.

Feedback control theory for dynamic traffic assignment

Traffic safety evaluation is one of the most important processes in analyzing transportation systems performance. Traditional methods like statistical models and before-after comparisons have many drawbacks, such as limited time periods, sample size problems, and reporting errors. The advancement of traffic conflict techniques combined with microsimulation offers a potentially innovative way for conducting safety assessment of traffic systems even before safety improvements are implemented. In this paper, simulation-based safety studies are reviewed, and a modified simulation-based surrogate safety measure and a new simulation-based surrogate safety measure that can capture the probability of collisions, as well as the severity of these potential collisions, are proposed. Conceptual and computational logic of the proposed surrogate safety indicators are described in detail. These surrogate safety indices are initially proposed for link-based analysis and should not be used for other purposes, such as intersection safety assessment, without further enhancements, and the use of these indices should be limited to the analysis of linear conflicts. In addition, these link-based indices are extended to be able to conduct aggregate networkwide safety assessments. The proposed indices are validated by means of a well-calibrated traffic simulation model of a section of the New Jersey Turnpike and real accident data from the same section. Preliminary results indicate a strong relationship between the proposed surrogate safety measures and real accident data. Further research is needed to investigate these new surrogate safety indices under different locations and traffic conditions.

Ascertaining viability of WiFi based vehicle-to-vehicle network for traffic information dissemination

A steady-state M/M/c queueing system under batch service interruptions is introduced to model the traffic flow on a roadway link subject to incidents. When a traffic incident happens, either all lanes or part of a lane is closed to the traffic. As such, we model these interruptions either as complete service disruptions where none of the servers work or partial failures where servers work at a reduced service rate. We analyze this system in steady-state and present a scheme to obtain the stationary number of vehicles on a link. For those links with large c values, the closed-form solution of M/M/[infinity] queues under batch service interruptions can be used as an approximation. We present simulation results that show the validity of the queueing models in the computation of average travel times.

Stochastic Humanitarian Inventory Control Model for Disaster Planning

Modelling and Problem Formulation.- Dynamic Traffic Routing Problem in Distributed Parameter Setting.- Fuzzy Feedback Control for Dynamic Traffic Routing.- Feedback Linearization for Dynamic Traffic Routing.- Sliding Mode Control for Dynamic Traffic Routing.- Network Level problem: System Optimal.- Network Level Problem: User Equilibrium.

LIFE-CYCLE COST ANALYSIS: STATE OF THE PRACTICE VERSUS STATE OF THE ART

Traffic congestion has become a part of daily life for most of us. One possible way of preventing congestion from building up is by disseminating traffic information. Today a number of commercial solutions exist for disseminating traffic information (e.g., Traffic.com, Metrocommute, Etak-Traffic). However, these solutions are plagued by prohibitive deployment and maintenance cost that prevents widespread deployment. As an alternative, solutions based on peer-to-peer architecture have been proposed. This results in a vehicular ad hoc network that is never connected because of the large geographical extent of a typical transportation network. We examine the characteristics of such a network and whether it can support effective traffic information dissemination.

Impact of probabilistic road capacity constraints on the spatial distribution of hurricane evacuation shelter capacities

The impacts of disasters have recently attracted increased attention from researchers and policy makers. However, there has been little consensus about how an efficient inventory management model can be developed for postdisaster conditions. Victims of a disaster are generally gathered into shelters during and after a severe disaster to ensure their security. Many evacuees do not have the financial resources to leave the disaster area or to find food, drugs, and other necessities. Hence, their vital needs should be supplied efficiently throughout the disaster and postdisaster periods. Without an adequate stock of goods, satisfying the daily requirements of the victims without disruption might be problematic. To solve this problem, humanitarian inventory control models that can aid in adequately responding to a disaster or a humanitarian crisis are needed. In this context, response represents preparedness, planning, assessment, appeal, mobilization, procurement, transportation, warehousing, and distribution. This paper is concerned with the development of a subproblem of the general humanitarian supply chain problem: an efficient and quick-response humanitarian inventory management model able to determine the safety stock that will prevent disruptions at a minimal cost. The humanitarian inventory management problem is first mathematically formulated as a version of the Hungarian Inventory Control Model. A solution to this time-dependent stochastic model is then proposed by using the p-level efficient points algorithm. The single commodity case results are given, and a sensitivity analysis of the model vis-à-vis various model parameters that affect safe inventory levels is conducted.

The time-dependent shortest pair of disjoint paths problem: Complexity, models, and algorithms

Life-cycle cost analysis (LCCA) is increasingly gaining recognition by the transportation community as an indispensable practice if the sustainability of its infrastructure systems is to be realized. The product of a 3-year study that assessed the LCCA practice in state highway agencies (SHAs) is presented. The study examined how LCCA practice changed in two decades, surveyed the way LCCA is practiced currently at SHAs in the United States, and reviewed how this evaluation technique is deliberated by the academics and researchers in the engineering and economics domains. Results of this study prove noteworthy in the inspection of an observed gap between the state of the practice and state of the art of LCCA. After all, that gap set up grounds for the noted mistrust in the credibility of LCCA. In addition to study results, an analysis of the observed gap and its causes is presented as well as recommendations for what can be done to bridge that gap. It is hoped that this will prove valuable for practitioners conducting LCCA, for policy makers, and for researchers carrying out studies on various topics related to LCCA.

Evacuation Network Modeling via Dynamic Traffic Assignment with Probabilistic Demand and Capacity Constraints

The focus of this study is on determining the change in capacity requirements and desirable shelter locations as a result of link capacity changes during evacuation. A cell transmission-based system optimal dynamic traffic assignment (SO-DTA) formulation first proposed by Ziliaskopoulos is extended by introducing probabilistic capacity constraints. The p-level efficient points method first proposed by Prékopa is used to deal with probabilistic capacity constraints of the proposed stochastic SO-DTA model. The model captures the probabilistic nature of link capacities that change in response to the impacts of events such as hurricanes and earthquakes that can destroy or damage highway links. First, a simple single-destination example network is studied to show the effectiveness of the proposed model. Then the impact of using stochastic and deterministic link capacities is also analyzed with a simplified multiple-origin, multiple-destination version of the Cape May, New Jersey, network. Desirable shelter locations are evaluated by letting the stochastic SO-DTA model assign flows generating the minimum systemwide travel time. The results indicate that introducing probabilistic link capacities can adjust the overall flow in the network as well as shelter utilization. Thus, if planners consider the predictions of the deterministic model, they may face the risk of not having sufficient food, medicine, and other emergency supplies in shelters. This paper suggests a more realistic approach to evacuation planning to avoid the inefficiencies that created problems after such recent major disasters as Hurricane Katrina and the tsunami in Southeast Asia.