In preparation for the UN Climate Summit in Copenhagen (November 2009), MIT has been doing some interesting projects using technology to understand the dynamics of how cyclists and pedestrians experience the city.
The Copenhagen Wheel aims to develop technology to use bicycles as moving sensors to map the flow of people and environmental conditions.
Cyclists using the SmartBiking system get green credits for using their bikes thanks to a smart tag system installed on bikes. It is sort of like the opposite of congestion charging.
This article in Wired looks at the social networking side of the technology and systems used in this project.
By using mobile phone technology the City has been able to gather real time data on crowds in Copenhagen. Since mobile phones are almost universally used and each mobile phone is constantly in touch with the network it is possible to map how crowds gather in real time.