What is congestion, in the UK, and in London?
The London Assembly's Transport Committee defines congestion with some difficulty in its recent report, "The future of road congestion in London" (June 2011) and relates congestion to journey time reliability, and the mayor's strategy for "Smoothing traffic flow" (mainly, it seems, for commercial or motorised traffic).
"The traditional measure of congestion, traffic speed, is problematic when used in isolation. This is because it fails to take into account the way road space is allocated or that average speed can mask unpredictable changes in the flow of traffic. Increasingly, TfL is placing an emphasis on journey time reliability as an important measure of congestion." (pp12-13) This London Assembly report claims to address "all road users" in London, but seems to be concerned mainly with motorised road users, taking traffic to mean motor traffic. The ubiquitous SCOOT junction control systems do not even take into account pedestrians or cyclists at all.
The House of Commons Transport Committee, in a report applicable nationwide, "Out of the jam, reducing congestion on our roads" (15 Sep 2011) includes pedestrian congestion in town centres, as well as congestion on A Roads and on Motorways "like the M25" within its scope. Transport for London's Head of Streets, Garrett Emmerson actually cited "pedestrians disobeying traffic signals" in the report as a cause of road congestion (p7), implying that pedestrians are not part of the traffic flow, but in opposition, even on streets in London.
A website has recently been launched to help travellers in London to predict increased congestion and journey times during the Olympics Games this year. In all of the work on road congestion (as it is called, rather than street congestion) it is interesting that non-motorised traffic on public highways, including cyclists and pedestrians on footways, is not captured statistically nor regarded as significant for balancing road users in a hierarchy. The hierarchy of users on streets (MfS) ought to be very topical in the current debate about streets in London, especially for non- motorised users.
Verkehrsexperten unterscheiden zwischen „Stau” und „stockendem Verkehr”. In der Schweiz beispielsweise wird „fachlich“ von einem Stau gesprochen, wenn der Verkehr mindestens für eine Minute mit weniger als 10 km/h fließt. Liegt die Geschwindigkeit im Bereich zwischen 10 und 30 km/h, spricht man von stockendem Verkehr.