Why adding a road can increase traffic and other modelling delights
MY LEAFY, fairly affluent corner of south London has a congestion problem, and to solve it, there is a plan to close certain roads. You can imagine the furore: the trunk of every kerbside tree sports a protest sign. How can shutting off roads improve traffic flows?
German mathematician Braess answered this question back in 1968, showing that adding a road to a network can actually increase travel times due to a boost in drivers using the same routes and therefore increasing traffic. Now a new book, Atlas of Forecasts: Modeling and mapping desirable futures by Katy Börner, uses it as a fine example of how a mathematical model predicts and can be used to resolve a real-world problem.
This and more than 1300 other models, maps and forecasts are referenced in Börner’s latest atlas, the third to be derived from Indiana University’s travelling exhibit Places & Spaces: Mapping science.
Her first, Atlas of Science: Visualizing what we know revealed the power of maps in science, while the second, Atlas of Knowledge: Anyone can map, focused on visualisation. In her latest foray, Börner wants to show how models, maps and forecasts inform decision-making in education, science, technology and policy-making.
