Six-Wave Odometer Panel for Evaluation of Voluntary Travel Behavior Change Programs

Abstract

A six-wave panel survey of household vehicle use in Adelaide, South Australia, and Melbourne, Victoria, was reviewed, with odometer readings as the key measurement. The study was conducted to explore the feasibility of using this method to evaluate the effectiveness of voluntary travel behavior change (VTBC) projects implemented at the household level. Odometer surveys are a practically feasible, publicly acceptable, and reliable method for measuring change in household vehicle use. The collection of odometer readings was chosen because it was a direct way to quantify distance traveled in private vehicles that was difficult to manipulate or misreport. The panel design was useful to minimize variation, and burden was reduced by keeping the task simple. Although the sample obtained may have been subject to coverage error, the demography of the sample is stable over time; this status indicates that there is no selective dropout from particular population segments. The data collected in this pilot suggest that sample sizes upwards of 1,000 households would be necessary to conclude with 95% confidence that an actual difference in daily vehicle kilometers traveled (VKT) per vehicle of ±1 km was significantly different from zero. Although the data here show that the average daily VKT per household and per vehicle in Adelaide stayed stable for VTBC nonparticipants and dropped in participating VTBC households, the small sample size means it cannot be stated with statistical confidence whether this was significant.