For the pollution mockup stream we decided to simulate one sensor for each of the traffic sensor at the exact location of this traffic sensor. We have provided values for carbon_monoxide, nitrogen_dioxide, sulfure_dioxide, particulate_matter and ozone index levels according to
http://en.wikipedia.org/wiki/Air_Pollution_Index

The stream generation works as follows: each sensor measurement (e.g. carbon dioxide) is initially assigned a value between 25 and 100. Every 5 minutes, the values will be updated as follows:

- if the value was below 20 before, it will now be the last value + random integer between 1 and 10

- if the value was higher than 210, it will now be the last value - random integer between 1 and 10

- else the value will be last value + a random integer between -5 and 5

This way the measurements won't erratically jump between low and high values and represent a more realistic stream but still won't go out of bounds (unrealistically low or high values)