Event Type: Seminar

With wireless communication devices becoming ubiquitous, Advanced Transportation Information Systems based on Inter-Vehicle Communication (IVC) are receiving increasing attention due to their fast response to incidents and resilience to disasters. In such IVC systems, vehicles equipped with wireless devices form a mobile ad hoc network, whose multi-hop connectivity is an important performance measurement. This talk presents an analytical recursive model and a Monte Carlo simulation model for computing the probability for two equipped vehicles or road-side stations to be connected through IVC. These models are derived based on the assumption that inter-vehicle communication is instantaneous with respect to vehicle movement and the concept of Most-Forwarded-within-Range communication chains. The two models, which cross-validate each other, are able to capture the impact of traffic patterns on IVC and yield results consistent with those in literature. Some future research directions will also be discussed.

Dr. Joseph (Yossi) Berechman is a CN Chair Professor in Transportation and International Logistics, Sauder School of Business, the University of British Columbia, Canada. Dr. Berechman has received his Bachelor degree from the Hebrew University in Jerusalem, Israel, and his Master and Ph.D. degrees from the University of Pennsylvania in Philadelphia. His major research interests are transportation economics and planning, transportation and land use, and policy analysis. He has published numerous journal papers and four books, the most recent one on transportation investment and economic development. Presently, his major interests focus on the evaluation and selection of large scale transportation infrastructure investment projects.

For ninety years, the principal means of financing transportation facilities in America has been through user fees, primarily motor fuel taxes and tolls. Motor fuel tax revenues have been plummeting for a variety of reasons, but there is no longer the political will to increase motor vehicle taxes. Rising costs and decreasing revenues have combined to bankrupt the transportation program, especially at the state level. At the same time, local governments all over the country, led by the example of California, have been enacting local option transportation taxes; gradually, the locus of transportation decision making has been shifting to local governments. Is this trend in finance good? Do most Americans even know that it is happening? What does the longer term future hold? In this seminar, Professor Wachs will argue that the recent trend is significant yet not viable in the longer term. While a variety of electronic user fees hold more promise, the transition to this approach will take decades and should be carefully planned starting now.

The resurgence of air traffic in the U.S. has focused attention on the need for improved policies and methods for airport congestion pricing. In this presentation, I establish a simple rule for the computation of airport congestion tolls that reflects the internalization of congestion. My theory argues that the airport toll system should not fully charge each airline for the congestion damage caused by an extra flight (as would be suggested by the standard road-pricing rule). Instead, an airline should only pay for the congestion damage it imposes on other carriers. This rule is easy to implement and could help policy makers design proper toll systems at airports worldwide. I test its validity within a realistic network structure containing multiple hub airports.

Road pricing can enhance public transportation by increasing its speed and service frequency. I examine these effects with a model of local bus service in London’s city center. The model focuses on four considerations: the cost savings to transit users and operators from reduced road congestion; the service improvements made feasible by increased ridership; the potential pass-through of operator cost savings as fare reductions; and the resulting multiplier effects on ridership and service offerings. I apply the model using data from the first few months of a February 2003 pricing program. Simulation results suggest significant effects even if pricing revenues had not been used to augment the transit budget as they were in London: a ridership increase of 11%, a service increase of 7% and user cost savings equivalent to 38% of the fare. Net benefits from these effects are equal to 39% of initial operator costs. These effects, but not the net benefits, are even larger in cities with more typical values for bus subsidies and initial modal share.

What are the prospects for economic development in lagging sub-national
regions? What are the roles of public infrastructure investments and fiscal
incentives in influencing the location and performance of industrial activity?
To examine these issues, I estimate a spatial probit function for industrial
activity in Brazil that explicitly incorporates infrastructure and fiscal
improvements in the cost structure of individual firms. Using firm-level data
from a 2001 annual industrial survey and regional/ spatial data at the micro-
regional level, I find considerable firm-level cost savings from location in
areas with relatively lower transportation costs to large markets. In
comparison, fiscal incentives have modest effects on firm-level costs.
Although this suggests that firms benefit from locations with good access to
markets, it does not necessarily suggest that improving inter-regional
connectivity will help lagging regions. Improving inter-regional connectivity
implicitly reduces a natural tariff barrier so firms that currently serve large
markets and benefit from economies of scale can more easily expand into
new markets in competition with local producers. Thus, producers in the
leading regions can crowd out local producers, with detrimental effects on
production and employment in the lagging region.

Advances in wireless technologies have stimulated interest in the use of inter-vehicle communication as the foundation of decentralized advanced transportation information systems. In this seminar, I discuss the reliability of inter-vehicle communication in a traffic stream, dependent on the distribution of equipped vehicles. Assuming that information propagation is instantaneous compared to vehicle movements, I measure reliability as the probability of success that information will travel beyond a specified location. I present stochastic models for both uniform and general traffic streams. In the models, I divide the traffic stream into a series of cells based on the transmission range, clarify the structure of possible most-forward-within-range communication chains, regressively compute the probabilities for information to travel to and beyond a vehicle at a certain hop, and determine the lower bound of the absolute success rate for information to travel beyond a point. Based on the models, I examine the performance of information propagation for different penetration rates, transmission ranges and traffic scenarios that include gaps and shock waves. I conclude by discussing implications and extensions of this effort.

Daily traffic assignments on a large-scale road network are described for ‘build’ and
‘no-build’ scenarios to evaluate the addition of two proposed ramps between I-295
and SR-42 in the New Jersey part of the Delaware Valley Region. The road network
consists of 39,800 links connecting 1,510 zones. The user-equilibrium traffic
assignment problem was solved with a new algorithm called origin-based assignment
(OBA) that can achieve highly converged solutions with reasonable computing effort.
The stability of link flow differences between the two scenarios in the vicinity of the
proposed ramps are examined over a broad range of assignment convergence levels.
Then, link flow differences over this range of convergence levels are compared to link
flow differences between two very highly converged solutions. The findings reveal
that a relative gap of 0.01% (0.0001) is required to ensure that the traffic
assignments are sufficiently converged to achieve link flow stability. These
convergence levels are then interpreted in terms of the number of Frank-Wolfe
iterations and computational effort required to achieve comparable relative gaps.

Microscopic traffic simulators — tools that realistically emulate the flow of individual vehicles in a road network — provide a reliable means of testing and evaluating the anticipated benefits of large transportation investments. These tools can capture the full dynamics of time-dependent traffic phenomena and account for drivers’ reactions to ITS technologies and strategies. This seminar will introduce the main features of the AIMSUN microscopic traffic simulation system and illustrate its use in two recent projects: the design and testing of an adaptive tunnel traffic management system (the Saint Gothard tunnel in Switzerland) and the ISM advanced network-level traffic management system in Germany’s State of Hessen. These case studies address a new domain for traffic simulation: support of traffic management decisions. The seminar will conclude with a presentation and discussion of enhancements to the AIMSUN system specifically designed to support traffic management decision making.