Inclusive design is about more than just giving people options, it's about enabling people to take the same options as everyone else. How we deal with changes in level is perhaps one area which shows this off in sharp relief.
It is a certainty that we'll have to design for level changes because the world isn't flat However, they way in which we deal with those changes can make all the difference. Consider this example from Great Yarmouth;
There's nothing revolutionary or flash about the layout and one can even ask why there are steps at all. However, some people do prefer to use steps and so having a ramp and steps next to each would allow a group of people to broadly stay together as they change level and so in my book, this is a pretty inclusive layout.
The photograph above is a ramp and step combination which I saw recently in Salford. It works hard to fit into limited space and again (as far as possible) allows a group of people to keep together whether they use steps or ramp.
Ramps do need a heck of a lot of space and the greater the change in level, the greater the length of ramp needed. In the UK, it's something of a tragic design classic that we end up building bridges and underpasses with twisting ramps to fit them into as smaller space as possible like this dystopian mess of an example from the many footbridges crossing the High Speed 1 railway.
This sort of outcome is often because the desire line isn't considered. Bridges like this will often have the desire line for people placed perpendicularly to the obstruction to be crossed and unless space is provided either side to simply lift and drop the desire line, we get convolution. In terms of inclusive design, this bridge is nothing like the elegant solution of the Yarmouth example as people cannot cross as a group.
Compare the HS1 bridge with this bridge in Cambridge which doesn't bother with steps, as the gentle ramp allows people to pass in groups whether as pedestrian or cyclist
Much of the design thought depends on the context of course. Whilst we can have surface level pedestrian (and cycle) crossings over busy high speed roads, we don't provide them in the UK in general unless they are associated with a junction. Bridges require a greater change in level to get the lorry headroom, whereas underpasses for people require less, even if designed for people riding horses. In this photograph, the Dutch ably show how to get a cycle track under a road;
Crossing rivers will depend on whether or not they are navigable or what is needed in terms of coping with flood events. Railways need certain headroom for the trains (obviously) and whether or not they have overhead power cables.
The key to much of this goes back to the simple provision of infrastructure which follows the desire lines for those people for whom the use of energy to move is the most critical. Get it right and the experience will be better for everyone.