research report

Policy and Literature Review on the Effect Millennials Have on Vehicle Miles Traveled, Greenhouse Gas Emissions, and the Built Environment

Abstract

Vehicle travel has reduced substantially across all demographics in the 2000s, but millennials or young adults born between 1985-2000 stand out as the group that has reduced vehicle travel the most. This reduction of travel among millennials is known as the millennial effect. This policy and literature review discusses insights from recent policy reports and literature regarding the millennial effect and identifies the prominent themes and gaps in knowledge. The first section reviews existing research on the millennial effect on vehicle miles traveled (VMT). The second section discusses the influence of the built environment on the travel and activities of the millennial generation. The third section highlights scenarios describing the millennial effect’s potential magnitude and identifies topics for consideration in future scenario planning efforts. The final section discusses the uncertainty that exists regarding the future behavior of millennials and their influence on vehicle miles traveled and greenhouse gas emissions.

research report

CTM-based optimal signal control strategies in urban networks

Abstract

This research introduces a novel analytical framework in deriving invariant averaged models for signalized intersections in urban networks, using the capability of the cell transmission model (CTM) to capture the detailed traffic dynamics such as the formation, propagation, and dissipation of congestion arising at network junctions. Generally, the CTM formulates the optimization problem as a mixed-integer linear-programming (MILP) problem, which introduce many binary variables for large-scale urban networks and is difficult to solve. The approach aims to derive invariant averaged models to eliminate the binary variables introduced by the traffic signals. For the purpose of simplicity, the approach emphasizes on a signalized linear junction connecting one upstream link with one downstream link. Using the Cell Transmission Model (CTM) simulation on a signalized ring road, the authors demonstrate that the invariant averaged model is a reasonable approximation to the original supply-demand model with binary signals. Due to the existence of merging behaviors, the authors introduce two new terms while deriving the averaged model: Effective Demand and Merging Priority. With these two new terms, the authors follow similar procedures as those in the linear junction, and derive the corresponding invariant averaged model for the merging junction. The authors further show that the derived averaged model for the signalized linear junction is just one special case of the one for the signalized merging junction with empty demand in one of the upstream links.

research report

Air Quality and Greenhouse Gas Benefits of an Advanced Low-NOx Compressed Natural Gas Engine in Medium- and Heavy-Duty Vehicles in California

Abstract

The goal of this research is to assess the greenhouse gas (GHG) emissions and air quality (AQ) impacts of transitions to advanced low‐NOx Compressed Natural Gas (CNG) engines in medium-duty vehicle (MDV) and heavy-duty vehicle (HDV) applications in California with a particular emphasis on renewable natural gas (RNG) as a fueling pathway. To evaluate regional air quality impacts in 2035, pollutant emissions from all end-use sectors are projected from current levels and spatially and temporally resolved. Scenarios are constructed beginning with both a conservative (Base Case) and more optimistic (SIP) case regarding advanced vehicle technology and fuel integration to provide a spanning of potential impacts. To capture the impact of seasonal dynamics on pollutant formation and fate, two modeling periods are conducted including a winter and summer episode. To estimate the potential GHG impacts of transitions to advanced CNG engines in HDV and MDV, scenarios are evaluated under various assumptions regarding fuel pathways to meet CNG demand from a life cycle perspective. Scenarios are compared to the baseline cases assuming (1) all CNG is provided from conventional fossil natural gas and (2) under a range of possible resource availabilities associated with renewable natural gas and renewable synthetic natural gas (RSNG) from in-state resources. Key findings include: i) expanding the deployment of advanced CNG MDV and HDV can reduce summer ground-level ozone concentrations and ground-level PM2.5 in key regions of California; ii) the largest AQ benefits are associated with reducing emissions from HDV; iii) in-state renewable natural gas pathways can meet the CNG demand estimated for both baseline cases; iv) in-state resources are unable to entirely meet CNG demand for the high total CNG demand estimated for the majority of Base alternative cases, and v) advanced CNG HDV and MDV can moderately reduce GHG emissions if fossil natural gas is used (14 to 26%).

research report

Transit Investment Impacts on Land Use Beyond the Half-Mile Mark

Abstract

This project examines the impacts of light rail transit investments on broader vicinity areas in Los Angeles County. This project found that the land use impacts of public transit investments are not necessarily confined to the half-mile boundary around station areas, although substantial variation exists by transit line.  While the areas beyond the half-mile mark were often excluded from conventional transit-oriented planning processes, these areas show a distinct pattern of land use transformation. Areas beyond the half-mile mark had a higher rate of development for several urban purposes, particularly after a few years have elapsed since the opening of nearby transit lines/stations.

research report

The Effect of Trucks Dispatch Decisions on Pavement Damage and Other Externalities

Abstract

External costs of freight trucks include air pollution, highway damage, and congestion. While diesel taxes reduce both the pollution and congestion externalities, the research paper shows that they worsen highway damage. The research team investigates the impact of fuel prices on cargo shipments using weight-in-motion data from New York and California. The paper includes sensor readings on over 1.4 billion vehicle events. These data allow us to track daily changes in the weight and number of trucks at specific locations. The researchers explain the average daily weight differential between New York and California as a function of the diesel price differential using unexpected weather as an instrument. The team finds that when fuel prices increase by 10 percent, fuel use by heavy trucks declines by 3.1 percent and average truck weight increases by 3.2 percent. While total truck traffic decreases by around 1 percent, on net there is 19.6 percent more road damage. The dispatch effect changes the welfare comparison of using fuel taxes versus efficiency standards to control carbon emissions. The researchers find that a reduction in per-mile shipping cost from the standard causes freight to be reallocated across more trucks so that schedules are enhanced—that is, the rebound occurs on both a quality and a quantity dimension. In consequence, road damage declines. While there is considerable uncertainty about the cost of external congestion and the safety of trucks, the research team finds that fuel efficiency standards dominate fuel taxes as a policy to reduce carbon emissions for a wide range of parameter estimates.

research report

A Unified Framework for Analyzing and Designing for Stationary Arterial Networks

Abstract

This research aims to develop a unified theoretical and simulation framework for analyzing and designing signals for stationary arterial networks. Existing traffic flow models used in design and analysis of signal control strategies are either too simple to be realistic or too detailed to be efficient. In this research we apply the link transmission model to formulate, analyze, and simulate traffic dynamics in a signalized arterial network. We first analytically derive approximate macroscopic fundamental diagrams for stationary traffic patterns with different network topologies, road conditions, driving behaviors, and signal settings. We then analyze congestion mitigation effects of different signal settings, including cycle lengths, green splits, and offsets. We further formulate and solve an optimization problem with the network flow-rate as performance measure to find optimal signal control parameters. We derived simple formulas for the optimal signal cycle length and offset under different traffic conditions to improve arterial network performance.

Phd Dissertation

Routing and Scheduling Problems of Container Trucks in a Shared Resource Environment

Publication Date

May 30, 2017

Author(s)

Abstract

More frequent vehicle movements are required for moving containers in a local area due to low unit volume that a single vehicle can handle compared with vessels and rails involved in the container supply chain. For this reason, truck operations for moving containers significantly affect not only transportation cost itself but also product price. They have inherent operational inefficiencies associated with empty container movements and container processes at facilities such as warehouses, distribution centers and intermodal terminals. One critical issue facing the trucking industry is the pressing need for truck routing plans that reduce such inefficiencies. Hence, this dissertation proposes to apply the concept of sharing resources, which is an emerging economic model, to container truck operations in order to resolve this issue. Two shareable resources – vehicles and containers – are considered.

This study extends the literature on routing and scheduling problems that arise from container movements, and examines the possible benefits of sharing resources across customers. A series of truck container routing and scheduling problems were developed by assuming different levels of resource sharing among; (1) customers of one trucking operator, (2) customers across collaborations of multiple operators, and (3) customers over multi-day operations. To enable a trucking company to operate its fleet under a shared resource environment, two operational strategies – street turning and decoupling operations – together with temporal precedence constraints – in addition to the time constraints that are typically included in the vehicle routing problem with time windows (VRPTW) – were adopted to address the proposed problems.

Two meta-heuristic algorithms based on a variable neighborhood search (VNS) scheme were developed to solve the proposed problems, including temporal precedence constraints – which are computationally more expensive – for real-world applications. To address flexible time windows resulting from temporal precedence constraints, a novel feasibility check algorithm was developed.

Results from a series of numerical experiments confirm that the proposed approach leverages the advantages of resource sharing, and the meta-heuristic algorithms are efficient solution approaches for each problem with the targeted resource sharing. Consequently, this dissertation offers a platform for the development of a decision-support tool for drayage companies by applying three different levels of resource sharing into their operations.

policy brief

Advanced Low-NOx Compressed Natural Gas Engines in Medium- and Heavy-Duty Vehicles Are Poised to Deliver Air Quality Benefits and Advance California’s Climate Goals

Abstract

Recent commercialization of advanced low-nitrogen oxides (NOx) Compressed Natural Gas (CNG) engines for medium- (MDV) and heavy-duty (HDV) vehicles has garnered significant interest due to the potential air quality benefits. Further, utilizing renewable natural gas (RNG) in advanced CNG engines from sources such as biomass and/ or biogas can achieve reductions in greenhouse gas (GHG) relative to using petroleum fuels and fossil CNG. However, the regional air quality and GHG reduction benefits of large‐scale deployment of advanced CNG trucks are currently unclear. Further, more information is required regarding RNG production potential from California instate biofuel resources, including potential supply volumes and production pathways that provide maximum GHG reductions. The UC Irvine Advanced Power and Energy Program assessed the air quality and GHG implications of transitioning to advanced CNG engines in MDVs and HDVs in California by developing and comparing different future adoption scenarios. The research team also leveraged prior research of biogas and biomass resources in California to consider different options for producing RNG in-state. Key findings from this research are highlighted in the following section.

research report

A Literature Review: Improving How Active Transportation Demand is Modeled and Evaluated

Abstract

Local transportation agencies typically rely on traditional travel demand forecasting models that focus on highway and roadway improvements to optimize vehicular traffic.  These models are not equipped to evaluate active transportation strategies which align with current State of California policies such as reducing vehicle miles traveled to cut greenhouse gas emissions and fostering active transportation modes.  In this context, ITS at UC Irvine (ITS Irvine) was invited by the Orange County Transportation Authority (OCTA) to propose, develop, and apply an approach to better model active transportation. This report represents the first phase of this work, which is a review of the recent literature on how to model demand for active transportation and an examination of OCTAM’s (OCTA’s own regional travel demand model) Active Transportation (AT) modeling tool to evaluate its potential for modification or incorporation into a new active transportation model. The following observations/suggestions are offered in this report: First, OCTAM Active Transportation does not include variables that could impact people’s decision to leave their vehicles at home in favor of transit. Second, a number of conditions need to be jointly met for people to walk or bike. Third, OCTAM Active Transportation does not capture residential self-selection, which could be important here as people who do not plan to walk/bike self-select into car-oriented neighborhoods.