working paper

Health Impacts of Moving Freight In and Our of the Ports of Long Beach and Los Angeles

Abstract

A number of strategies could reduce emissions along active freight corridors like the SPBP. These include: intelligent transportation systems (ITS), advanced traffic operations and control measures, shifting freight from trucks to trains, and increased use of clean-diesel trucks. The health impacts of such strategies should be closely studied in coming years. Our analysis is being expanded to measure health impacts of trucks not only on freeways that feed directly into the port, but also on nearby local streets and other freeways in the corridor.

published journal article

Broadcasting safety information in vehicular networks: issues and approaches

Abstract

A primary goal of intelligent transportation systems is to improve road safety. The ability of vehicles to communicate is a promising way to alleviate traffic accidents by reducing the response time associated with human reaction to nearby drivers. Vehicle mobility patterns caused by varying traffic dynamics and travel behavior lead to considerable complexity in the efficiency and reliability of vehicular communication networks. This causes two major routing issues: the broadcast storm problem and the network disconnection problem. In this article we review broadcast communication in vehicular communication networks and mechanisms to alleviate the broadcast storm problem. Moreover, we introduce vehicular safety applications, discuss network design considerations, and characterize broadcast protocols in vehicular networks.

published journal article

Air Pollution Impacts of Shifting San Pedro Bay Ports Freight from Truck to Rail in Southern California

Abstract

Escalating concerns about air quality in southern California have led authorities at the Ports of Los Angeles and Long Beach, also known as the San Pedro Bay Ports (SPBP), to adopt a number of measures designed to mitigate emissions. One way to do this is to shift some of the containers currently transported by drayage trucks to trains. This alternative is attractive because it would decrease congestion and air pollution on the area’s main freeways (I-710 and I-110) and the arterials that serve the SPBP. In addition, it would increase road safety along the busy Alameda freight corridor between the SPBP and downtown Los Angeles. One drawback would be an increase in pollutant emissions from train operations in the Alameda corridor; however, trains tend to pollute less than trucks per ton-mile, and new federal regulations are tightening the emissions standards for diesel locomotives. The goal of this paper is to quantify the net impact of such a modal shift on the emission of particulate matter (PM) and nitrogen oxides (NOx), the two air pollutants of most concern in the SPBP area. This analysis relies on microscopic simulation to capture emissions resulting from stop-and-go traffic on the freeways serving the SPBP. It was found that emissions of both NOx and particles less than 2.5 μm in diameter (PM2.5) can be significantly reduced by switching from drayage trucks to trains. This finding suggests that a modal shift should be encouraged, especially if there is unused train capacity and if the shift does not conflict with the shippers’ interests.

working paper

Joint Modelling of Attitudes and Behaviour in Project Evaluation: Case Study of Single-Occupant Vehicle Toll Use of Carpool Lanes in San Diego, California

Abstract

Knowing what people think about the usefulness, fairness, and success of new transport initiatives is vital information for planners and project evaluators. Methods for studying the complex relationships between attitudes and choice behaviour need to be included in evaluation processes. 

The attitudes of an individual faced with a new transport option will depend in part on whether the individual can take advantage of the new option, whether he or she actually chooses to take advantage, and the perceived benefits of the option, to the individual and to the community. Transport planners use choice models to understand factors affecting demand, but modelling of attitudes has not received similar attention. In this paper we demonstrate how a joint model of attitudes and behaviour can be used in comprehensive project evaluation. The approach involves analysing attitude survey data using a structural equations model designed for use with discrete choice and ordinal-scale variables. 

Our application involves the evaluation of responses to a project that allows solo drivers to pay a fee to use a carpool, or high-occupancy vehicle (HOV) lane facility on the Interstate 15 (1-15) Freeway in San Diego. The attitude survey is of subscribers to the program and a random sample of other freeway users. Four endogenous variables are explained as functions of each other and of exogenous variables such as income, household composition, age and gender. These endogenous variables are: (1) choice of subscription to the program, (2) mode choice of carpooling versus solo driving, (3) perception of the seriousness of the traffic congestion on the route, and (4) attitude towards allowing solo drivers to pay to save time by using the carpool lanes.

working paper

Can HOT Lanes Encourage Carpooling? A Case Study of Carpooling Behavior on the 91 Express Lanes

Abstract

This paper is a case study of carpooling behavior on the 91 Express Lanes. The 91 Express Lanes are the nation’s first implementation of High Occupancy/Toll (HOT) lanes where carpools with three or more passengers could use the lanes for free (at the time the data for this study was collected) and others pay a toll that varies by time of day to use the premium Express Lane. One concern over such a policy is that people won’t carpool if they can just pay for the travel time savings that they would normally obtain by carpooling and using a High Occupancy Vehicle (HOV) lane. Our survey data show that the rate of carpooling did not change much between the opening of the Express Lanes and now, there is a lot of changing between modes (increases and decreases in the number of passengers), there are a large number of people that carpool a few times a week, and that HOV-2s use both the regular lanes and the Express Lanes. We further investigate whether HOT lanes encourage carpooling by modeling carpool formation with discrete choice models. The results show that mode choice behavior in the corridor is similar to carpooling behavior in other locations and carpooling in the corridor is not discouraged.

working paper

Development of a Microscopic Activity-Based Framework for Analyzing the Potential Impact of Transportation Control Measures on Vehicle Emissions

Publication Date

June 30, 1998

Abstract

The 1990 Clean Air Act Amendments (CAAA) and the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA) have defined a set of transportation control measures to counter the increase in the vehicle emissions and energy consumption due to increased travel. The value of these TCM strategies is unknown as there is limited data available to measure the travel effects of individual TCM strategies and the models are inadequate in forecasting changes in travel behavior resulting from these strategies. The work described in this paper begins to provide an operational methodology to overcome these difficulties so that the impacts of the policy mandates of both CAAA and ISTEA can be assessed. Although the framework, as currently developed, falls well short of actually forecasting changes in traveler behavior relative to policy options designed to encourage emissions reduction, the approach can be useful in estimating upper bounds of certain policy alternatives in reducing vehicle emissions. Subject to this important limitation, the potential of transportation policy options to alleviate vehicle emissions is examined in a comprehensive activity-based approach. Conclusions are drawn relative to the potential emissions savings that can be expected from efficient trip chaining behavior, ridesharing among household members, as well as from technological advances in vehicle emissions control devices represented by replacing all of the vehicles in the fleet by vehicles conforming to present-day emissions technology.

working paper

Rational Response to Irrational Attitudes: The Level of the Gasoline Tax in the United States

Publication Date

June 30, 1998

Author(s)

Abstract

Retailers often price items at $9.99 rather than $10.00. They may do so to fool consumers into viewing the price as closer to $9.00 than to $10.00, or to signal consumers that the product is on sale (e.g., Stiving and Winer, 1997). Similarly, workers highly desire a six-figure income-a salary of $100,000 sounds much more impressive than a salary of $99,999. 

This paper explores related behavior by government. Suppose legislators attempt to reduce the salience of increases in the gasoline tax by avoiding moving gasoline taxes into double digits, and suppose that once taxes are moved beyond the double-digit threshold, legislators might as well raise them a little more than just the threshold increment to compensate for the increased visibility they have incurred. Two patterns might result: relatively few states imposing a tax of exactly 10 cents, and a more general avoidance of double-digit taxes. The data confirm this pattern. 

Such attention to nominal values can lead to peculiarities. Consider the following thought experiment. A state is observed to impose a tax of 8 cents on a gallon of gasoline. But were it forced to specify the tax as so many cents per quart, it would impose a tax not of 2 cents per quart, but of 3 cents per quart. Were such behavior common, then to explain the level of taxes it would be necessary to consider not only the usual economic and political explanations, but also the nominal value of taxes. 

In the following we present two different ways of testing for the importance of nominal values. Our focus is on gasoline taxes in the different states in the United States. Such taxes are both substantively important, and well suited for study since much data are available on them.

Phd Dissertation

Markovian decision control for traffic signal systems

Abstract

A typical urban traffic network is a very complicated large-scale stochastic system which consists of many interconnected signalized traffic intersections. Setting signals at intersections so that the traffic in such a network flows efficiently is a key goal in traffic management. The conventional traffic signal control algorithms assume the traffic system is deterministic; most of them use data aggregation, instead of a mathematical model, and apply off-line, heuristic control strategies which do not respond to the fluctuations of the traffic flows in the network. In this dissertation, the traffic signal control problem is formulated as a decision-making problem for a stochastic dynamical system. Based on Markovian decision theory, a new decentralized optimal control strategy with the embedded platoon dispersion model is developed to minimize the queue length and the steady state delay of traffic networks. A rolling horizon algorithm is also employed to achieve real-time adaptive traffic signal control. Statistical analysis of the computer simulation results for this approach indicates significant improvement over the traditional fully actuated control, especially under the conditions of high, but not saturated, traffic demand.

working paper

Road Pricing for Congestion Management: The Transition from Theory to Policy

Publication Date

December 31, 1997

Author(s)

Abstract

Traffic congestion is a classic externality, especially pervasive in urban areas. The theoretical and empirical relationships governing it have been thoroughly studied. As a result, most urban economists and a growing number of other policy analysts agree that the best policy to deal with it would be some form of congestion pricing. Such a policy involves charging a substantial fee for operating a motor vehicle at times and places where there is insufficient road capacity to easily accommodate demand. The intention is to alter people’s travel behavior enough to reduce congestion.