https://en.wikipedia.org/wiki/Google_Traffic
Google Traffic works by analyzing the GPS-determined locations transmitted to Google by a large number of mobile phone users. By calculating the speed of users along a length of road, Google is able to generate a live traffic map.[2]
The reports are updated every minute but while my ipad auto updates the PC has to be refreshed manually.
The only error is that they don't show traffic parallel to the drop off zone but only to the now restricted CTA roundabout which will always show as free flowing as passengers now follow a different route.