Measuring generalised transport costs as an indicator of accessibility changes over time

• Changes in generalised transport costs are computed on a national level.
• Generalised transport costs changes are used to measure an important part of accessibility changes.
• Policy makers may use generalised costs instead of narrow indicators such as time delays.
• Improved generalised costs information may also be used in transport models.
• Generalised transport costs rise over time because of an increasing value-of-time.

Accessibility in transport policy documents is usually measured through partial indicators such as road speeds, traffic queues or train fares. In the literature, more advanced indicators are found, based on e.g. market potential or utility-based methods. This paper presents a generalised transport costs indicator for policy making which incorporates financial costs, travel times, and reliability of travel times. It calculates the average costs per kilometre of trips by transport mode, trip purpose, trip distance, region and time-of-day.A case study for the Netherlands shows that generalised transport costs by private car rose by 6% between 2000 and 2007. The main causes were increasing fuel costs and values-of-time. Average travel speed has increased despite more congestion on the trunk road network. Generalised costs of train trips have also risen by about 6%, because of an increase in train fare prices and the value-of-time. The time costs have, however, been reduced by improved reliability. Long-term scenarios without new policies also show an increase in generalised costs, both for cars and trains.The generalised transport costs indicator is not a panacea which can measure every aspect of accessibility, but it does represent an important step towards a more comprehensive approach to presenting accessibility changes for policy making.