Reducing Personal Vehicle Kilometers Travelled to Decrease Air Pollution in Durham, NC

Abstract

Durham, North Carolina is at the center of the metropolitan region known as the Research Triangle. This area is experiencing rapid and sprawling growth. In addition, there is a lack of substantial public transportation, which results in a high level of reliance on personal automobiles. This research aims to examine how reliance on personal automobiles in one aspect of the lives of residents, the daily work commute, can be reduced in order to reduce aggregate vehicle kilometers travelled (VKTs). The transportation mode choices of walking, bicycling, busing, carpooling and vanpooling were examined as potential mode choices that commuters could switch to if given an economic incentive to do so.

A set of equations were developed based on EPA mobile source emissions models and regional data to determine how reductions in VKTs could affect air pollution emissions. A contingent choice survey was developed and sent, via email, to a sample of employees of Duke University and Hospital, in order to determine the marginal willingness to accept payment for an alternative commute. A mode choice model was developed using logit regression techniques based on the survey results to extrapolate the behaviors to employees of Duke at large and commuters to the City of Durham. A log-transformed bid variable was determined to be the most appropriate functional form to predict the likelihood of switching modes. Finally, marginal economic damages of air pollutants were obtained from peer-reviewed research and the economically efficient level of potential benefits were estimated.

The air quality models showed that the criteria air pollutants examined were dealt with well under existing policy. Concerning Carbon Dioxide, the resulting calculations showed that only when the marginal damages of pollution are quite high do the equated marginal benefits provided to a person to reduce their commuting footprint begin to have substantial impacts on VKTs.