As a Business Economics/Earth Science double major, John Naviaux was very interested in financially practical approaches to solving environmental issues. His study of public transportation emissions synthesized his interests in economics and the environment. John’s research calculates an economic value for the emissions savings of bus transportation, and is unique in being one of the first to rely on ridership data collected from the field. Along with this research, John has tried to use his undergraduate years to learn as much as possible about every possible subject. Pursuing his broad range of interests, he conducted a summer 2011 particle physics research project in Geneva, Switzerland.

The emission benefits of public transportation are primarily realized during periods of high ridership. This research quantifies the emission benefits of buses by calculating the mile-weighted average ridership for the Orange County Transportation Authority (OCTA) bus system in Southern California. Ten routes were randomly selected, and data was collected on passenger counts, boardings, alightings, time of day, and distance between stops. The average ridership was calculated to be 14.49 riders per mile. Once non-revenue vehicle miles are accounted for, OCTA buses emit 20,000–51,000 fewer metric tons of CO2 than an equivalent number of passengers would if they were transported by car. Using EPA valuations for the social cost of carbon, this decrease provides an annual savings of $109,800–$279,990 domestically, and $724,200–$1,846,710 globally. OCTA receives approximately $480 million in subsides from state and federal sources each year, so an analysis focusing solely on CO2 emissions must conclude that OCTA’s emission benefits are not enough on their own to justify their subsidy. The emission benefits calculated for OCTA likely represent an ideal case. OCTA ranks 18th in the U.S. in number of passenger miles traveled and has completely switched its buses from diesel to natural gas fuels. Other bus systems using less emission-efficient fuels will provide an even smaller benefit.

David Brownstone School of Social Sciences

John Naviaux’s thesis clearly shows that there are no significant CO2 emissions benefits from moving a traveler from a personal automobile to an Orange County urban bus. This is a strong negative result since the Orange County bus fleet is among the cleanest in the world with almost all buses running on natural gas, and this shows that it will be difficult to reduce CO2 emissions in the U.S. by simply getting more people to use urban mass transit. This thesis is an excellent example of the benefits of doing a good, thorough job on a “small” problem. The data collection is only feasible for a few bus lines, but by careful selection of these lines John was able to obtain important results.