Such data as we have can give only an indication of the answer. In October 2003, survey forms were handed to northbound drivers at some of the tollbooths on a weekday. Of those returning forms, 709 out of 3,253 (about 22 per cent) indicated that their journeys began in Kent or East Sussex (figures were not broken down for Kent alone) and finished in Essex. From a postal survey of tag users at about the same time, the equivalent figure was 708 out of 1,589 respondents (approx 45 per cent). About 23 per cent of trips are paid for using tags.