The opportunity Value of Travel Time (VTT) is one of the most important parts of the total cost of recreation day-trips and arguably the most difficult to estimate. Most studies build upon the theoretical framework proposed by Becker’s (1965) by using a combination of revealed and stated preference data to estimate a value of time which is uniform in all activities and under all circumstances. This restriction is relaxed by DeSerpa’s (1971) model which allows the value of saving time to be activity-specific. We present the first analysis which uses actual driving choices between open access and toll roads to estimate a VTT specific for recreation trips, thereby providing a value which conforms to both Becker’s and DeSerpa’s models. Using these findings we conduct a Monte Carlo simulation to identify generalizable results for use in subsequent valuation studies.