In the context of inter-urban motorists' route choices and the travel time savings offered by the UK's first toll motorway, a range of SP exercises tested various contextual and design effects. The design aspects relate to how the marginal benefit of time savings is influenced by the size and sign of the time saving, task complexity, presentation format, and whether the choice context is real. The contextual factors cover the impact of journey duration, attribute credibility, and where in the journey the time savings occur. The conclusions are largely credible but in some cases challenge established views and contribute significantly to understanding in this area
