Direct video measurements of surface street truck traffic at eleven intersections and line segments in communities adjacent to southern California ports document that volumes of port-related trucks often reach 400-600 per hour for several hours, immediately upwind of ‘sensitive’ land uses such as schools, open-field parks and residences. The diurnal fluctuation of trucks on surface streets varies by intersection, local conditions, and passenger car commute patterns. Our data provide new insights into the geographic distribution and intensity of truck traffic associated with the increase in goods movement, and are essential for reliably modeling pollutant exposures in port-adjacent communities.

Traffic exposure assessments could misclassify the extent and locations of exposure if traditional recall surveys and self-reported travel diaries do not record all participant activities. The Harbor Communities Time Location Study (HCTLS) examines the nature, extent and implications of underreported locations/trips in a case study which used portable Global Positioning Systems (GPS) devices to track the diurnal patterns and traffic exposure of 47 residents of communities near the Los Angeles-Long Beach port complex. Participants were similar to adults nationwide in time spent indoors, in-vehicle, and outdoors, but spent more time indoors at home (78% vs. 66%). Overall, participants did not report nearly half (49%) of the locations and trips identified in GPS-enhanced data on their activity diaries, resulting in about 3 h/day in unreported locations and 0.6 h/day in unreported trips. The probability of a location/trip being under-reported was systematically correlated with participant and location/trip characteristics. Self-reported data missed about 50 min of heightened air pollution exposures during the 5 h/day on average participants spent in high-traffic areas and about 30 min during the 4 h/day near truck routes. GPS-enhanced methods provide opportunities to more precisely characterize exposure periods and tools to identify facility, roadway, and land use types of the greatest concern for mitigation efforts.

We assessed child care facilities' proximity to heavily traveled roadways in an attempt to estimate the extent of potential exposure of young children to vehicle-related pollution in this understudied microenvironment.

We examined approximately 24,000 licensed child care facilities in California located within 200 m of heavily traveled roadways.

Approximately 57000 of the available slots in California child care centers (7% of the overall capacity) are in facilities located within 200 m (650 ft) of roadways averaging 50000 or more vehicles per day, and another 172000 (21%) are in facilities located within 200 m of roadways averaging 25,000 to 49,000 vehicles per day. Facilities providing care to infants or preschool-aged children and facilities located in disadvantaged areas were more often situated in medium-or high-traffic areas.

Additional research is needed to further clarify the significance of the child care microenvironment in terms of potential childhood exposures to vehicle-related pollutants. Design strategies, notification standards, and distance-based siting restrictions should be considered in the facility licensing process and in land use and transportation planning.