Masters Theses

Date of Award

5-1994

Degree Type

Thesis

Degree Name

Master of Science

Major

Environmental Engineering

Major Professor

Terry L. Miller

Committee Members

Wayne Davis, James Smoot

Abstract

The research resulted in development of a technique and application of the technique to determine the effects of traffic demand management and traffic control measures applied to the Brentwood, Tennessee, Interstate 65 transportation corridor on aggregate daily vehicular emissions of global warming gases. Traffic control measures in the corridor consisted of construction of high occupancy vehicle lanes for Interstate 65 and resequenced signalization on major arterial roadways in the corridor study area. Traffic demand management involved implementation of van pooling where thirty vans were utilized to transport workplace commuters and, thereby, alleviate passenger automobile traffic. Four temporal states were analyzed preconstruction of high occupancy vehicle lanes without traffic demand management or traffic control measure implementation, construction ongoing without implementation of traffic demand management or traffic control measures, construction ongoing with partial traffic demand management and traffic control measure implementation and the phase of construction completed with full traffic demand management and traffic control measure implementation.

The global warming gases considered were carbon dioxide, carbon monoxide, nitrogen oxides, methane hydrocarbons, and non-methane hydrocarbons. Except for carbon dioxide, emissions of each of the gases were determined by utilizing the United States Environmental Protection Agency's MOBILE5 emissions model with inputs of roadway average daily traffic, roadway average speeds, and a roadway vehicular mix of eight vehicle type classifications. Carbon dioxide emissions were derived by assuming that carbon dioxide emissions are directly proportional to vehicle fuel consumption. This method of carbon dioxide emissions analysis is an original contribution of the study. Fuel consumption data for various types of vehicles were utilized to obtain carbon dioxide emissions. The global warming effects of each of the gases were characterized by quantifying the respective gas emissions in terms of mass emissions of carbon dioxide that would result in a global warming effects equal to that of the respective gas considered - a global warming potential.

The research resulted in a determination of global warming potential changes over the four temporal phases of the Brentwood traffic demand management project. Results showed variation in global warming potential and attempted to explain the changes. A surprising result of a net increase in global warming potential of the vehicular exhaust emissions from the preconstruction phase to the full transportation demand management phase was obtained. This appeared to result from an increase in vehicular traffic as a result of greater roadway utilization and higher corridor average speeds. From the traffic data utilized, the traffic demand management, while providing increased roadway utility, actually result in an increased global warming potential in terms of both absolute emissions and emissions per vehicle mile travelled.

However, due to the limited scope of the traffic data utilized (essentially only one traffic input data set observation per project phase), no conclusion could be statistically supported other than the conclusion that a more complete traffic flow data set was required one that would include multiple observations of traffic parameters at given points in time for the respective project phases so that statistical confidence limits could be derived.

An ancillary task of the research resulted in micro-scale modeling of maximum carbon monoxide concentrations for a major roadway intersection in the study corridor for the pre-construction phase and post construction, full traffic demand management phase of the Brentwood project. The Environmental Protection Agency's CAL3QHC dispersion model was use for this task. Results of one hour maximum concentrations showed relatively low carbon monoxide concentrations emanating from the roadways modeled for the two phases and a generally increased concentration in the full transportation demand management implementation phase as compared to the preconstruction and no transportation demand management implementation phase. In both phases, the derived maximum carbon monoxide concentration results were lower than the one hour average concentration national ambient air quality standard of thirty-five parts per million. Maximum concentrations, however, approached the limits of the eight hour average national ambient standard for carbon monoxide of eight parts per million. These results, too, were dependant on traffic data so, conclusions regarding changes in concentrations could not be statistically supported.

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