This is the method of journey to work data (CT0045) from the 2011 Census. The data provides he number of people aged 16-74 commuting to work via various modes of transport.
The information is produced using both a person's place of work and their method of travel to work and is comparable with 2001. For example, a person who has indicated their place of work as their home address and said that they travel to work by driving a car or van (eg visiting clients) appears in the category "Work mainly at or from home", as was the case in 2001. This compares with QS701EW which solely uses a person's method of travel to work. In the above example, the person would appear in the category "Driving a car or van".
The 2011 census in England and Wales took place on 27th March 2011. It provides a snapshot of the population and its characteristics on that day.
In order to protect against disclosure of personal information from the 2011 Census, there has been swapping of records in the Census database between different geographic areas, and so some counts will be affected. In the main, the greatest effects will be at the lowest geographies, since the record swapping is targeted towards those households with unusual characteristics in small areas.
Further information about the census estimates, including details about the methodology is available here: http://www.ons.gov.uk/ons/guide-method/census/2011/index.html