For the last few years at least, Heathrow Express has been conducting research on how its existing customers might change their behaviour when Crossrail comes.
It's obviously tracking research, as the questionnaires generally ask similar questions each time, but as more information has been published about Crossrail services, presumably they are able to monitor any associated changes in customer perception.
The questionnaires present scenarios and ask respondents to rate their likelihood of choosing different options, including the Tube.
It gets down to asking things like potential pricing comparisons, whether you start or end your journey from home or work, whether your journey might start or in the core and whether you might have luggage, or whether you generally travel hand-luggage only for journeys commencing in the core, in which case how would the lack of dedicated luggage space and the potential for no seats affect you.
It has even asked how much work you do in the last hours before you make a journey by air, presumably again looking at the difference between on board environments and their suitability for laptops.
Separately, Heathrow Express does currently offer concessions to Heathrow and airline employees, including cabin and flight crew, so it's perhaps worth mentioning that a proportion of passengers are not travelling at a public fare.
