Abstract
An empirical study was undertaken of congested patterns at highway bottlenecks. On the basis of statistical data it was found that the spatial-temporal structure of congested patterns possesses some predictable features. From these features a classification of congested patterns was made. It was found that the most frequently observed congested pattern is the general pattern (GP). In GP synchronized flow occurs upstream of a bottleneck and wide moving jams spontaneously emerge in that synchronized flow. Capacity in free flow can be about twice as high as capacity in congested traffic upstream of the on-ramp if the GP has formed.