During the last decade physicists, engineers and computer scientists have joined in an enormously fruitful dialogue about traffic and granular flow. Cars and sand grains have in common, that they interact irreversibly, which is the reason for similar jamming phenomena. The main difference is that car drivers choose their destination and route individually, while grains follow external driving forces. This book gives an overview about the progress in modelling, computer simulation, experiments and field observations, which was reached within the last two years. The contributions are based on the International Workshop Traffic and Granular Flow ’01, which took place in Nagoya, 15 – 17 October 2001. Topics include a critical classification of models for highway traffic, new technological applications, friction and arching phenomena in pedestrian traffic, scale free networks and internet traffic, instabilities and fluctuations in avalanches and granular pipe flow.