The US National Parks Service (NPS) has long led the way in providing decent trails, signage and information for its millions of visitors of varying mobility. Take a look at any of their park webpages (this one for Yellowstone as an example) and you’ll find plenty of detailed material for those with hearing or visual impairment, as well as for travellers using wheelchairs.
The NPS have now gone a step further with their Accessibility Guide to the Grand Canyon. This is a downloadable pdf from their main Grand Canyon accessibility page, and is also available in large-print form. The guide includes maps with accessible lookout points and trails, useful phone numbers and suitable ranger programs. More guides should follow for other US parks, and one can only hope that other countries copy this example and offer their disabled visitors the same level of assistance.