Thanks for putting forward this suggestion. Our Feature Requests list is already very long, so realistically it’s probably not something we'd be able to look into for some time I'm afraid, as it's joining the back of a very long queue. Also, I think it may be very difficult to find a reliable data source for this information. We've added it to our Feature Requests list though (number 140) , where people can vote for it.
This website has it all... for all of us - healthy individuals. I am aching to provide all those less fortunate ones the maximum oppertunity possible, to enjoy nature not less than us!! I've been doing much research, and the availability of routes especially with a gpx download is extremely small (like 1:20 - where varified accessible routes is one, and general routes is 20!).
I am therefore asking as a favour, if you would please consider adding an 'accessibility checker', where one can upload / plot a route, and see any accessability issues. (I'm sure you can get funding for this).
it is worthwile noting, that although I mentioned accessible - as in wheelchair access, the amount of parents with prams, wishing to just explore and enjoy nature, is large enough aswell.