A Bi-Objective Approach to Evaluate Highway Routing and Regulatory Strategies for Hazardous Materials Transportation

Hazardous materials (hazmat) transportation is of concern to policymakers because of the serious safety, health, and environmental risks associated with the release of hazmat. One effective approach to minimize risks associated with hazmat transport is the prohibition of hazmat transportation on higher risk links that either pose safety hazards or increased exposure by traversing densely populated areas. Because of high risk, there are multiple stakeholders involved in hazmat transportation. While shippers and carriers are directly involved in making routing decisions, regulatory agencies influence this decision by imposing routing restrictions. In this paper, we apply a bi-objective shortest path problem to evaluate routing and regulation plans for hazmat transportation. We characterize the cost objective as the shortest path between an origin and a destination. The risk objective is to minimize the risk of exposure by restricting the link with the highest risk on the best available path from an origin to a destination. We formulate the bi-objective model and apply it to a test network. Solutions consider multiple origin-destination pairs and present a non-dominated frontier to establish routing and regulatory strategies for hazmat transportation

Urban Core Transit Access to Low-Income Jobs

In many areas in the United States, low-income jobs have followed patterns of suburbanization, with a resulting spatial mismatch between low-income workers residing in dense urban areas and low-income jobs located in suburban areas of the outlying urban periphery. This situation facilitates a need for auto ownership in core urban areas traditionally thought to be rich in transit supply and robust in transit accessibility. The resulting auto dependence is a substantial economic burden for low-income households and detrimental to those who have made residential location choices in an attempt to adopt a lifestyle that relies on public transit. This paper seeks to explain the various levels of households with low incomes and high rates of car ownership (LIHCO households) in the urban core by investigating their accessibility to low-income job locations. Two transit accessibility metrics geared toward low-income populations were derived and were applied. The first metric was based on the number of low-income jobs accessible by transit from the residential location; the second was based on late-night transit frequency at the residential location. These accessibility scores were then correlated with the magnitude of LIHCO households residing in each spatial unit of analysis. The results suggested a link between transit access to low-income jobs, late-night transit frequency, and the number of LIHCO households. It was concluded that improved transit access to low-income jobs and increased late-night transit frequency might reduce auto ownership in LIHCO households, with improved economic welfare as a result

Exact and heuristic methods for public transit circulator design

This work presents a new mixed integer model for a single-route circulator design problem. An exact method that performs well in practice on medium-sized networks is presented that utilizes 1-trees as lower bounds and a stopping criterion relevant in non-Steiner networks. Proof of the correctness of this stopping criterion is provided. A heuristic method is presented for large networks. Both methods are tested on sample networks along a commuter rail line in Austin, TX in several problem variations and results of these tests presented. The practical and theoretical implications of this work are outlined

Exact and heuristic methods for public transit circulator design

This work presents a new mixed integer model for a single-route circulator design problem. An exact method that performs well in practice on medium-sized networks is presented that utilizes 1-trees as lower bounds and a stopping criterion relevant in non-Steiner networks. Proof of the correctness of this stopping criterion is provided. A heuristic method is presented for large networks. Both methods are tested on sample networks along a commuter rail line in Austin, TX in several problem variations and results of these tests presented. The practical and theoretical implications of this work are outlined.Circulator Transit network design Feeder Shuttle Optimization Public transportation

Commuter Rail Circulator Route Network Design and Its Implications for Transit Accessibility

The success of a commuter rail system depends on cultivating a ridership base on which to expand the system. Cultivating this ridership depends on offering a quality transportation option to commuters. Characteristics of commuter rail systems in the United States present significant challenges. Commuter rail has been implemented only on existing rail right-of-way (ROW) and infrastructure in the United States. Existing rail ROW does not often coincide with current commercial and residential demand centers and necessitates the use of a circulator system to improve the accessibility of the system. The commuter rail circulator network design problem (CRCNDP) addresses a particular aspect of the commuter rail trip, seeking to improve the performance of the entire system through accurately modeling the portion of the trip from rail station to the final destination. This final leg includes the trip on the circulator vehicle and the walking trip from the circulator stop to the final destination. A detailed description of the CRCNDP is provided, as well as a case study that will seek to illuminate the performance of the CRCNDP using three operational strategies

Measuring Service Gaps Accessibility-Based Transit Need Index

The integration of transit needs into transit accessibility indexing is important for evaluating existing transportation systems and service gaps and for identifying priority areas for investments in transportation infrastructure. This study detailed an indexing model for accessibility of transit need and focused on the necessity of evaluating transit needs and transit accessibility simultaneously. A need index was developed to identify areas in high need of public transit services from economic and sociodemographic information, and a composite accessibility index was developed to identify levels of access to transit services and shortcomings in providing service. The need for transit service was then modeled as the lack of transit accessibility, and the model correlated different access indicators with their ability to predict transit service need. This model mapped areas with different levels of transit accessibility and transit needs by using a single score, which may be easily interpreted by planners who examine transit equity. The model was applied to the city of Meriden, Connecticut, and results were compared with a general approach for consistency and effectiveness. The usefulness of the model was also highlighted through a representative example of the model\u27s application

An Aggregated Public Transit Accessibility Measure

Measuring the ease of access to the transit services is important in evaluating existing services, predicting travel demands, allocating transportation investments and making decisions on land use development. A new aggregated approach to assessing the accessibility of public transport is described to assist transit professionals in the planning and decision making process. It involves the use of readily available methods and represents a more holistic measure of transit accessibili-ty integrating developer, planner and operator perspectives. The paper reviews previous and cur-rent methods of measuring accessibility and selects three methods for application in a case study in Meriden, CT. Inconsistencies are noted across the methods, and a consistent grading scale is presented to standardize scores and ensure a better comparison of results. Finally, this paper pro-poses weighting factors for individual methods to formulate an aggregated measure based on in-dividual accessibility component measures. The approach aims to provide a robust and uniformly applicable measure of transit accessibility that can easily be interpreted by transit planners to identify shortcomings in service coverage and promote equity in transit accessibility in the com-munity

A Composite Index of Public Transit Accessibility

Measuring ease of access to transit services is important in evaluating existing services, predicting travel demands, allocating transportation investments, and making decisions on land development. A composite index to assessing accessibility of public transit is described. It involves use of readily-available methods and represents a more holistic measure of transit accessibility, integrating developer, planner, and operator perspectives. The paper reviews previous and current methods of measuring accessibility and selects three methods for application in a case study in Meriden, Connecticut. Inconsistencies are noted across the methods, and a consistent grading scale is presented to standardize scores. Finally, this paper proposes weighting factors for individual methods to formulate a composite measure based on individual accessibility component measures. The approach aims to provide a robust and uniformly applicable measure that can be interpreted easily by planners to identify shortcomings in service coverage and promote equity in transit accessibility in the community

A Bi-Objective Approach to Evaluate Highway Routing and Regulatory Strategies for Hazardous Materials Transportation

Hazardous materials (hazmat) transportation is of concern to policymakers because of the serious safety, health, and environmental risks associated with the release of hazmat. One effective approach to minimize risks associated with hazmat transport is the prohibition of hazmat transportation on higher risk links that either pose safety hazards or increased exposure by traversing densely populated areas. Because of high risk, there are multiple stakeholders involved in hazmat transportation. While shippers and carriers are directly involved in making routing decisions, regulatory agencies influence this decision by imposing routing restrictions. In this paper, we apply a bi-objective shortest path problem to evaluate routing and regulation plans for hazmat transportation. We characterize the cost objective as the shortest path between an origin and a destination. The risk objective is to minimize the risk of exposure by restricting the link with the highest risk on the best available path from an origin to a destination. We formulate the bi-objective model and apply it to a test network. Solutions consider multiple origin-destination pairs and present a non-dominated frontier to establish routing and regulatory strategies for hazmat transportation