working paper

Walking and Urban Form: Modeling and Testing Parental Decisions about Children’s Travel

Abstract

Over the past several years, the private vehicle has become the predominant mode of travel to school while walking and bicycling rates have decreased. Some suggest that this change in travel behavior contributes to negative health outcomes in children, including increased rates of 1) overweight/obesity through inactivity and 2) pedestrian and bicyclist fatality and injury. A series of recent policies and programs directly attribute the change in travel behavior to school to the urban form of communities. Limited research exists to support this hypothesis, however. The fundamental questions of whether and how urban form impacts a child’s trip to school must to be answered in order to develop effective interventions aimed at increasing rates of walking and bicycling activity and safety.

The research proposes a conceptual framework to examine the nature and shape of the relationships between urban form; interpersonal, demographic and social/cultural factors; parental decision-making and a child’s travel to school. Using parent survey data on children’s travel to school and urban design assessments from twelve elementary school neighborhoods, the relative influence of urban form on the mode choice to school was first determined. Results indicate that urban form elements such as street lights and street widths do affect the probability of a child walking or bicycling to school; however, the affect of these elements is modest compared to other influential variables such as the perceived convenience of driving, country of birth, family support of walking behavior, reported traffic conditions in the neighborhood and perceived distances between home and school.

A second analysis examined how urban form and children’s travel behavior relate by testing the hypothesis of an indirect relationship. The findings show that parent’s feelings of neighborhood safety, traffic safety and/or household transportation options do not intervene in the relationship between urban form and children’s travel behavior. Socio-demographic characteristics and parent’s attitudes toward travel, however, may modify the strength of the relationship between urban form and children’s travel behavior.

The results of this study advance the discussion on relationships between urban form, transportation and health and inform policy and practice of the best targets for future planning interventions.

working paper

Approximation Algorithms for the Bid Construction Problem in Combinatorial Auctions for the Procurement of Freight Transportation Contracts

Publication Date

December 31, 2002

Abstract

The bid valuation and construction problem for carriers facing combinatorial auctions for the procurement of freight transportation contracts is very difficult and involves the computation of a number of NP-hard sub problems. In this paper we examine computationally tractable approximation methods for estimating these values and constructing bids. The benefit of our approximation method is that it provides a way for carriers to construct optimal or near optimal bids by solving a single NP-hard problem. This represents a significant improvement in efficiency. In addition, this method can be extended to many other applications.

journal article preprint

Relationships Among Urban Freeway Accidents, Traffic Flow, Weather, and Lighting Conditions

Abstract

Linear and nonlinear multivariate statistical analyses are applied to determine how the types of accidents that occur on heavily used freeways in Southern California are related both to the flow of traffic and to weather and ambient lighting conditions. Traffic flow is measured in terms of time series of 30-second observations from inductive loop detectors in the vicinity of the accident prior to the time of its occurrence. Results indicate that the type of collision is strongly related to median traffic speed and to temporal variations in speed in the left and interior lanes. Hit-object collisions and collisions involving multiple vehicles that are associated with lane-change maneuvers are more likely to occur on wet roads, while rear-end collisions are more likely to occur on dry roads during daylight. Controlling for weather and lighting conditions, there is evidence that accident severity is influenced more by volume than by speed.

working paper

Transportation Energy Use

Publication Date

December 31, 2002

Abstract

This chapter forecasts transportation energy demand, for both the U.S. and California, for the next 20 years. Our guiding principle has been to concentrate our efforts on the most important segments of the market. We therefore provide detailed projections for gasoline (58 % of California transportation energy in 1988), jet fueI (17%), distillate (diesel) fuel (13%), and residual bunker) fuel (10%). We ignore the remaining 2%–natural gas, aviation gasoIine, liquefied petroleum gas, lubricants, and electricity. Although we discuss prospects for the use of alternative fuels such as methanoI and natural gas, we do not believe that these will be significant factors in the next 20 years. Table 2-1 gives an overview of transportation energy use in California and the U.S.

working paper

Combinatorial Auctions for Transportation Service Procurement: The Carrier Perspective

Publication Date

December 31, 2002

Abstract

The procurement of transportation services is an important task for shippers because of the need to control costs at the same time as providing high service levels. When shippers with goods and/or materials to transport seek transportation services from outside companies they typically put out a request for quotes from a set of carriers. They then assign contracts based on negotiated service charges. This process is similar to a simple sealed-bid auction in which each bidder submits a sealed bid for a single item. In the past, when shippers need to procure transportation services for a set of distinctive delivery routes (called lanes) they would obtain quotes for each lane individually and repeat the simple auction process for each lane. Alternatively, they might negotiate for bundles of lanes with a single carrier at a time. However, in the last few years software has been developed to allow shippers to make all lanes available for bidding simultaneously and to allow carriers to simultaneously bid upon combinations of individual lanes. This method of awarding contracts, conventionally called a combinatorial auction, has been reported to result in significant cost savings for shippers. Our research examines the benefits of combinatorial auctions primarily from the carrier’s perspective. Preliminary findings, based on a simple simulation model suggest that benefits for carriers can also be significant.

working paper

Electronic Integration in the Air Cargo Industry: An Information Processing Model of On-Time Performance

Publication Date

December 31, 2002

Author(s)

Abstract

This study examines electronic integration in logistics supply chains using the non-integrated US-international air cargo industry as a case study. We ask what impact electronic integration has on interorganizational task performance, and hypothesize about factors limiting the effectiveness of electronic integration. Surprisingly, our study does not find evidence of direct impacts of electronic integration on performance though it does find evidence of indirect impacts of information systems use and performance. The findings suggest that the use of electronic integration as a strategy to improve operational performance across firms is limited by the nature of the interorganizational task, environmental dynamism, and the power relationship between firms in the supply chain.

working paper

Evaluation of Potential ITS Strategies Under Non-Recurrent Congestion Using Microscopic Simulation

Publication Date

December 31, 2002

Author(s)

Lianyu Chu, Henry Liu, Will Recker

Abstract

This report presents a micro-simulation method to evaluate potential ITS applications. Based on the commercial PARAMICS model, a capability-enhanced PARAMICS simulation environment has been developed through integrating a number of plug- in modules implemented with Application Programming Interfaces (API). This enhanced PARAMICS simulation can thus have capabilities to model not only the target traffic conditions and operations but also various potential ITS strategies. An evaluation study on the effectiveness of potential ITS strategies under the incident scenarios is conducted over a corridor network located at the city of Irvine, California. The potential ITS strategies include incident management, local adaptive ramp metering, coordinated ramp metering, traveler information systems, and the combination of above. Based on the calibrated simulation model, we implement and evaluate these scenarios. The evaluation results show that all ITS strategies have positive effects on the network performance. Because of the network topology (one major freeway with two parallel arterial streets), real-time traveler information system has the greatest benefits among all single ITS components. The combination of several ITS components, such as the corridor control and the combination scenarios, can generate better benefits.

research report

New Highways, House Prices, and Urban Development: A Case Study of Toll Roads in Orange County, CA

Abstract

We examine the link between highways and urban development by employing both hedonic analysis and multiple sales techniques to study the impact of the construction of toll roads in Orange County, California, on house prices. Urban economic theory predicts that if highways improve accessibility, that accessibility premium will be reflected in higher land prices.

Our empirical analysis of house sales prices provide strong evidence that the toll roads, the Foothill Transportation Corridor Backbone in particular, created an accessibility premium; home buyers are willing to pay for the increased access that the new roads provide. Such willingness to pay influences both development patterns and, potentially, induced travel (the association between increases in highway capacity and increases in vehicles miles of travel). The results are consistent with the idea that induced travel is caused, in part, by changes in urban development patterns that are linked to increases in highway capacity .

working paper

Valuing Time and Reliability: Assessing the Evidence from Road Pricing Demonstrations

Publication Date

December 27, 2002

Abstract

This paper compares results from evaluations of two recent road pricing demonstrations in southern California. These demonstration projects provide particularly useful opportunities for measuring commuters’ values of time and reliability. Unlike most revealed preference studies of value of time, the choice to pay to use the toll facilities in these demonstrations is relatively independent from other travel choices such as whether to use public transit. Unlike most stated preference studies, the scenarios presented in these surveys are real ones that travelers have faced or know about from media coverage. By combining revealed and stated preference data, some of the studies have obtained enough independent variation in variables to disentangle effects of cost, time, and reliability, while still grounding the results in real behavior. Both sets of studies find that the value of time saved on the morning commute is quite high when based on revealed behavior (between $20 and $40 per hour), and more than 50% lower when based on hypothetical behavior. When satisfactorily identified, reliability is also valued quite highly. There is substantial heterogeneity in these values across the population, but it is difficult to isolate its exact origins.

working paper

Deployment Paths of ATIS: Impact on Commercial Vehicle Operations, Private Sector Providers and the Public Sector

Abstract

Most studies of the economic benefits of Advanced Traveler Information Systems (ATIS) have focused on the passenger transportation market. Few analyses have addressed the applications of ATIS to freight operations even though using ATIS to route or divert commercial vehicles can make a significant improvement in overall traffic flow and system performance. In this study, multivariate demand models were estimated based on large-scale surveys of commercial vehicle operators in California to determine the current use and perceptions of advanced information technologies, especially advanced traveler information systems (ATIS), among these firms. Data were used to identify organizational and operational characteristics that made these technologies more or less attractive, and to predict potential adoption of the technologies by carrier type. Many characteristics proved influential including company size, type and location of operation, length of load moves, provision of intermodal service and private versus for-hire status. A secondary goal was to explore the extent to which new logistics intermediaries,especially “infomediaries” are likely to develop advanced information technologies for the freight industry. Private sector providers of ATIS have not lived up to earlier expectations. While there still may be a significant future role for private sector involvement in providing this type of information, for now the burden appears to fall primarily on state and local transportation agencies.