Do ozone action day alerts modulate active transportation in Texas cities?

Ozone action days are issued in metropolitan areas of Texas when the following day’s ozone forecast is Unhealthy for Sensitive Groups or worse. Ozone action day alert language suggests that the public make contributing behavioral changes (i.e., reducing pollution by taking the bus instead of driving), as well as avoidance behavioral changes (i.e., avoiding pollution by staying inside). In this analysis, the effect of ozone action days on active transportation (bicycle or pedestrian) patterns at different times of the day is assessed for five metropolitan areas in Texas using multi-year observational data. The Austin-Round Rock, Dallas-Fort Worth, Houston-Galveston-Brazoria, and San Antonio metropolitan areas show changes in traffic patterns consistent with avoidance behavior, or a reduction in outdoor activity in the afternoon on ozone action days. In contrast, the El Paso metropolitan area shows changes in traffic patterns consistent with contributing behavior, or increased pedestrian traffic on ozone action days. In conclusion, ozone action day alerts do affect active transportation patterns in Texas, but the behavioral change is not uniform.