Have you noticed how sometimes when there are steps to access and exit a house, either at the front, back or side entrances that sometimes those steps can be a little steep for someone with limited mobility?
Sometimes a ramp is not necessary and also not the best choice but the steps in place, while only a few, maybe two to three steps or even just one in place may pose a problem.
This is where a half-step comes in handy, the height will usually be about half of any concrete step that you have in place and although its actually adding an additional step its lessening the height difference so that the step becomes much more manageable, and because the ground and paving slabs can sometimes be unlevel, you will often find that a half-step is adjustable on all four corners, so that you can adjust it to be level and not prone to wobbling.
This is a really simply solution to what can otherwise pose quite a problem and in cases where someone does try to tackle steps that they are finding too steep it can sometimes lead to rather nasty falls.
For the sake of an additional step to lessen that risk it can make the situation a whole lot easier and safer for a person with limited mobility.