Several hybrid regression models that predict hot stabilized vehicle fuel consumption and emission rates for light-duty vehicles and light-duty trucks are presented in this paper. Key input variables to these models are instantaneous vehicle speed and acceleration measurements. The energy and emission models described in this paper utilize data collected at the Oak Ridge National Laboratory (ORNL) that included fuel consumption and emission rate measurements (CO, HC, and NOx) for five light-duty vehicles and three light-duty trucks as a function of the vehicle’s instantaneous speed and acceleration levels. The fuel consumption and emission models are found to be highly accurate as compared to the ORNL data, with coefficients of determination ranging from 0.92 to 0.99. Given that the models utilize the vehicle’s instantaneous speed and acceleration levels as independent variables, these models are capable of evaluating the environmental impacts of operational-level projects including intelligent transporta...

Estimating vehicle fuel consumption and emissions based on instantaneous speed and acceleration levels

This paper discusses the nature, and magnitude, of externalities associated with automobile use, including local and global pollution, oil dependence, traffic congestion and traffic accidents. It then discusses current federal policies affecting these externalities, including fuel taxes, fuel-economy and emissions standards, and alternative fuel policies, summarizing, insofar as possible, the welfare effects of those policies. Finally, we discuss emerging pricing policies, including congestion tolls, and insurance reform, and we summarize what appears to be the appropriate combination of policies to address automobile externalities.

Automobile Externalities and Policies

This paper looks at the connection that transportation and land use share and the role this connection has in smart growth efforts. Four assumptions are presented that discuss the impact the highway construction and capacity might have on growth, on congestion, the impact that light rail transit may have on density, and the impact of new urbanism design strategies on automobile use. The paper provides an overview of the theory, research efforts, and current debates associated with the assumptions.

/pdf/smart-growth-and-the-transportation-land-use-connection-what-42xgssf7am.pdf

Smart Growth and the Transportation-Land Use Connection: What Does the Research Tell Us?

The theory of induced travel demand asserts that increases in highway capacity will induce additional growth in traffic. This can occur through a variety of behavioral mechanisms including mode shifts, route shifts, redistribution of trips, generation of new trips, and long run land use changes that create new trips and longer trips. The objective of this paper is to statistically test whether this effect exists and to empirically derive elasticity relationships between lane miles of road capacity and vehicle miles of travel (VMT). An analysis of US data on lane mileage and VMT by state is conducted. The data are disaggregated by road type (interstates, arterials, and collectors) as well as by urban and rural classifications. Various econometric specifications are tested using a fixed effect cross-sectional time series model and a set of equations by road type (using Zellner’s seemingly unrelated regression). Lane miles are found to generally have a statistically significant relationship with VMT of about 0.3–0.6 in the short run and between 0.7 and 1.0 in the long run. Elasticities are larger for models with more specific road types. A distributed lag model suggests a reasonable long-term lag structure. About 25% of VMT growth is estimated to be due to lane mile additions assuming historical rates of growth in road capacity. The results strongly support the hypothesis that added lane mileage can induce significant additional travel.

Relationships between highway capacity and induced vehicle travel

A study design procedure was developed and demonstrated for the deployment of portable onboard tailpipe emissions measurement systems for selected highway vehicles fueled by gasoline and E85 (a blend of 85% ethanol and 15% gasoline). Data collection, screening, processing, and analysis protocols were developed to assure data quality and to provide insights regarding quantification of real-world intravehicle variability in hot-stabilized emissions. Onboard systems provide representative real-world emissions measurements; however, onboard field studies are challenged by the observable but uncontrollable nature of traffic flow and ambient conditions. By characterizing intravehicle variability based on repeated data collection runs with the same driver/vehicle/route combinations, this study establishes the ability to develop stable modal emissions rates for idle, acceleration, cruise, and deceleration even in the face of uncontrollable external factors. For example, a consistent finding is that average emissions during acceleration are typically 5 times greater than during idle for hydrocarbons and carbon dioxide and 10 times greater for nitric oxide and carbon monoxide. A statistical method for comparing on-road emissions of different drivers is presented. Onboard data demonstrate the importance of accounting for the episodic nature of real-world emissions to help develop appropriate traffic and air quality management strategies.

https://www.tandfonline.com/doi/pdf/10.1080/10473289.2003.10466245

On-Road Measurement of Vehicle Tailpipe Emissions Using a Portable Instrument

To meet the regulatory requirements of the Clean Air Act Amendments of 1990, metropolitan planning organizations, state officials, legislators, and courts with oversight responsibilities are currently being asked to make judgments about the likely effects of highway capacity additions on air quality on the basis of their interpretation of the best available information. The Executive Committee of the Transportation Research Board initiated an 18-month study, the results of which are summarized in TRB Special Report 245, "Expanding Metropolitan Highways--Implications for Air Quality and Energy Use", to evaluate the scientific evidence about the impacts of highway capacity additions on traffic flow characteristics, travel demand, land use, vehicle emissions, air quality, and energy use in metropolitan areas. The TRB study does not resolve the broader debate--which involves value judgments about the relative importance of mobility, economic growth, environmental protection, and energy conservation--but it does review the state of knowledge and the reliability of forecasting tools available to planning agencies to predict the effects of expanding highway capacity on air quality and energy use. This article comments on the findings of the TRB study and presents the study's concluding observations.

N Humphrey

Papers

Expanding metropolitan highways: implications for air quality and energy use