Also do you take account of time spent waiting at traffic lights when calculating car and bus CO2 emissions? Going by car up our local main street (Dundas Street) to go up to the Royal Mile at George IV Bridge in the centre of Edinburgh you will go through 7 traffic lights in just over a mile. On average you will catch at least 4 of these on red, and could spend between half a minute and 2 minutes per light, depending on the junction. So that's perhaps 6 minutes belching out CO2 while stationary. During that time you might have gone another 2 miles of distance. I am not sure what the difference in emission between driving along the road and idling plus accelerating from stationary, but I would guess that a nominal one mile of distance might be more like two miles in emissions in this example. Presumably you could have an average emisson per traffic light factor to add to the emission per mile figure? Or do you do that already?

Incidentally, you mention people “pushing a pram or using a wheelchair”. Do you have the data available to include a “step-free” option on your routes?