Currently (October 2017), analysis of the traffic conditions in Cambridge is derived from the real-time positions of the region's buses. The data is presented in the form of 'transit times' of buses along pre-defined sections of road.

You can view this 'transit time' traffic date by clicking on the 'View' link on the Traffic item on the homepage

homepage screenshot

This will take you to the 'zones map' page:

traffic zones map

You can click on any of the displayed zones, and you will go to a chart plot showing the recorded 'transit times' across that zone. The data for this plot is created dynamically by tracking buses that enter the zone by crossing the GREEN line of the shape defining the zone, these buses are then tracked to confirm they do not leave the zone except by crossing the RED line, and the time (in seconds) of that particular journey is recorded as a 'zone transit' event.

traffic transits plot

As you move your mouse over the various dots on the 'plot', the available data detail is 'popped up' over the plot. In the example above a 'transit event' at 12:36:04 local time on 13th Oct 2017 is highlighted, showing the journey time across the 'Madingley Road In' shape was 108 seconds.

Please note where this data is for INBOUND traffic, e.g. as in this case with the zone "madingley_road_in", there is also data continually calculated for the opposite direction but we don't make this easy to see at the moment: you have to EDIT the url of the webpage from "madingley_road_in" to "madingley_road_out" and you'll see the plot for the inverse journeys. Apologies. We'll address this in due course.

This particular data source does NOT have reliable content for the added bus 'data', i.e. things like route or label information, and that is why we are relying entirely on the vehicle identifier, time and position information only to produce this plot. To clear up an oft-reported mystery, the colour-coding of the dots (yellow or grey) is purely a piece of 'debugging' information added to the plot at a very early stage to highlight which dots have route information vs. which have that missing.

The plot shown above can be considered 'normal' for that particular piece of road. The idea of the monitoring technique is that was can detect when the traffic is NOT normal, e.g. here on the same road for Thursday 5th Oct:

traffic transits plot