Over the past couple of months I have taken part in several workshops on the future of smart highways and smart cities. As you might expect, the discussions ranged far and wide but one common theme struck a chord with my early academic training in transportation. The workshop debates often led to a key feature of transportation networks that has been known for a long time, stemming from seminal work by John Wardrop in the mid-twentieth century: network optimum and traveler optimum are not the always the same.
If ‘smart’ means optimizing the use of resources and minimizing the external effects of travel, congestion and environmental effects, then which optimum will the system seek? This depends on whether we consider smart travelers or smart transportation networks.
A smart traveler gathers all the information available and uses it to find the best trip characteristics. For example, the time of travel, the modes used, the routes followed and the costs incurred according to the personal preferences that their smart technology has acquired – either directly or through learning from previous trips. These aims may not be entirely selfish, as travelers may seek to minimize their carbon footprint or the amount of exhaust pollution they emit. They may show further altruism by sharing information about the state of the network that they have observed, for example by using social media to give warnings of queues, or allowing data gathered during their journey to be used by a third party. However, they expect their smart mobility service to meet their personal requirements and not compromise any of them to meet someone else’s.
A smart transportation network gathers all available information and uses it to advise or control the trip characteristics in order to apportion scarce resources, create the best overall travel patterns for the network, and minimize negative travel experiences for both travelers and non-travelers. It may use information provided through the altruism of smart travelers but, if that is insufficient, it could be a result of an obligation that is part of the conditions that allow access to the network in question. In other words, if you want to use a smart network you must be prepared to share data about your movement across that network. The transportation network operator may seek to satisfy the needs of travelers but it will not do this to the detriment of optimizing the network as a whole.
Clearly smart travel applications and smart transportation network management need to recognize the existence of each other and find a way of working together. At some point individual travel options will start to impede each other to the point where
the individual can no longer obtain any benefit and the overall situation for the transportation network will be less than optimal. Ideally, before this situation arises the smart transportation network will be able to take over and work toward a transportation network optimum, even though individual travelers may still not be able to get the best possible routing. The mechanism by which this collaboration may be brought about is not yet clear, but without it, will either be smart enough to make a significant difference to the efficiency of travel in crowded urban areas?
Neil Hoose is an independent ITS consultant and owner/director of Bittern Consulting Limited firstname.lastname@example.org