The impact of traffic images on travel time valuation in stated-preference choice experiments

We develop a simple but modern stated-preference (SP) choice experiment to analyse the impact of traffic images on the estimated value of travel time savings (VTTS). A random subsample of survey respondents view computer-generated images that depict traffic conditions for congested and free-flow portions of hypothetical travel alternatives. The remaining respondents receive otherwise-identical surveys that only verbally describe the attributes of those alternatives. From surveys with images, the estimated VTTS is $7.40 per hour for congested travel time and $5.70 for free-flow travel time, implying a ‘congestion premium’ of 30%. From surveys without images, however, congested and free-flow VTTS estimates are identical at $5.90 per hour. Our results indicate that traffic images, however rudimentary, can substantially influence travel-time valuation, thus compelling further research on incorporating them into SP experimental design.