Samenvatting
The underlying mechanisms leading to the fundamental diagram of freeway traffic-flow are very complex in nature because of the multi- lane environment. A recent study revealed a strong lane-to lane coupling. This excludes a lane-wise approach, and necessitates to study the traffic stream as a whole. Implications for the fundamental diagram and capacity are checked. Some preliminary empirical results suggest that the shape of the diagram varies strongly under subtle, almost psychological changes.