The RGS-IBG annual conference has been on this week, and I presented as part of a series of geocomputation sessions arranged in advance of the 21st anniversary Geocomputation conference in Leeds next year. The topic was current CASA research from the RESOLUTION project, looking at developing fast and consistent methods of measuring public transport accessibility between different cities.
For this task I have been testing the OpenTripPlanner software with encouraging results. PDF of the slides are here.
The data used for the London analysis comes from the Traveline public transport timetable data. The image below shows an example accessibility measure of jobs accessible within 1 hour’s travel time leaving at 8am.
CityGeographics 
What would also be useful is the % jobs that workers actually reach within one hour’s travel time from each home location (TZ)
Hi Alan, that’s what the map shows if I’m understanding you correctly. The map is the percentage of jobs in the metro region accessible from each residential location (in this case MSOAs) within 1 hour’s travel time. It’s a typical Accessibility to Jobs indicator
Hi Duncan, nah I’m talking about the actual pattern of worker travel as revealed by HH travel surveys e.g. 80% of workers resident in zone x take (say) 30 minutes to get to from home to work door-to-door by car.
The data situation in the UK is that we have detailed data on the actual commuting flows and travel mode (from the census, see for example- https://citygeographics.org/2012/06/21/visualising-flows-great-britain-journey-to-work/), but not on travel time. So accessibility models like the above (once calibrated with small sample travel surveys) are the first step in getting spatially detailed info on commuting routes and times