Closer to the total?: Long distance travel of French mobile phone users

Abstract

Analysis of long-distance travel demand has become more relevant in recent times. The reason is the growing share of traffic induced by journeys related to remote activities, which are not part of daily life. In today?s mobile world, these journeys are responsible for almost 50 percent of the overall traffic. Traditionally, surveys have been used to gather data needed for the analysis of travel demand. Due to the high response burden and memory issues, respondents are known to underreport the number of journeys. The question of the real number of long-distance journeys remains unanswered without additional data sources. This paper is the first to quantify the underreporting of long-distance tour frequencies in travel diaries. We take a sample of mobile phone billing data covering 5 months and compare the observed long distance travel with the results of a national travel survey covering the same period and the same country. The comparison shows that most of the error estimates calculated by researchers so far are too low. Our work suggests that the number of long distance journeys is twice as high as reported in surveys. It is shown that there two different reasons causing for the underreporting. On the one hand, soft-refusals travelled long-distances, but reported no long-distance tours. On the other hand, respondents underestimate their number of long-distance tours. Consequently, there is a need to use alternative data sources in order to gain better estimates of long-distance travel demand.