Finally, it is worth pointing out that the techniques presented here represent an important advance in improving the accuracy of technical, economic and social viability studies for projects involving underground car parks. Apart from the work presented here it is also very important to get reliable information about the demand for future car parking. This is obtained by doing quality stated preferences surveys around the area where the car park will be constructed and, if there are available resources, complementing these surveys with household surveys which help us estimate more accurately the demand induced by the future car park.