The Effects of Ozone Action Day Public Advisories on Train Ridership in Chicago

Document Type

Journal Article

Publication Date


Subject Area

ridership - mode choice, mode - rail


Travel behavior, Ridership, Regression analysis, Regression, Rail transit, Public participation, Public involvement, Patronage (Transit ridership), Panel studies, Ozone alert programs, Ozone, Mode choice, Modal choice, Mobile sources, Local participation, Hours, Emission mitigation strategies, Citizen participation, Choice of transportation, Chicago (Illinois)


Ozone action day advisories are one type of voluntary mobile source emission reduction program for urban areas where ozone pollution is concentrated. When forecasts predict that ground level ozone will exceed healthy levels, public advisories urge citizens to voluntarily choose public transportation as a means of eliminating automobile trips and reducing mobile emissions. To obtain credit for emission reductions spurred by voluntary programs, states must provide verifiable reduction estimates. This paper applies a fixed effects regression model to a panel of hourly Chicago Transit Authority train ridership data to evaluate the potential effects of ozone action day advisories in Chicago from 2002 to 2003. Findings show the overall effect of ozone action days on train ridership is not significant. However, there are statistically significant changes in ridership patterns during some parts of the day. The findings also indicate that ozone advisories systematically alter the travel behavior of a small proportion of Chicago area travelers, making it possible to conclude that pollution advisories do have the potential to affect transportation choice and thereby contribute to voluntary reductions in ozone precursor emissions. These patterned effects on traveler behavior may result from substitution effects or scheduling effects.


Transportation Research Part D Home Page: