The travel cost method is based on the observation that recreational services can only be realised through physical access to nature. This implies that individuals seeking to enjoy the service will need to spend resources (time and money) to travel to the site. The travel activity is a reflection of the use value this service has to people. There are basically two different types of travel cost methods: one based on a valuation of a single site (appropriate when the site in question is of particular interest and significance) and one based on choices between multiple sites (appropriate when the researcher is interested in valuing the attributes of recreational sites, i.e. to determine the importance of environmental attributes, recreational facilities and accessibility, not simply site access).