Transportation Planning program researchers analyze passive, vehicle-based GPS data that are collected for a subsample of participants in households travel surveys. These GPS-derived trip data are compared with trip information reported by survey respondents in traditional travel diaries to quantify trip underreporting and misreporting. The trip-rate correction factors that are subsequently developed from these audits are applied to the larger survey sample to produce more accurate travel estimates for modeling purposes.
Additionally, program researchers have collected and analyzed GPS data for the purpose of estimating vehicular travel time and delay stratified by roadway functional classification and urban area type in various cities in Texas.
Transportation Planning researchers conduct spatial analyses and attribute queries in GIS-based platforms to ensure traffic analysis zone (TAZ) information and geocoded address coordinates for household, workplace, external, and commercial vehicle surveys are accurate. Researchers also develop impedance matrices for assigning travel times and lengths to vehicle trips reported by survey participants. Additionally, researchers in the Transportation Planning program process and overlay GPS-derived trip data on local street networks with plotted household and work locations for visual inspection, assessment, and correction of the GPS trip related data.