For a person in a wheelchair, getting from one place to another on flat ground or a one-floor building involves enough problems without having to contend with grade changes. Being able to get from one floor to another isn't that big of a deal in a building with an elevator, but it can be almost impossible otherwise.
A change in elevation of a mere six inches cannot be accomplished without a ramp designed with just minimal rise. Traversing a four-foot or more change can only be handled by using mobility lifts. These are designed specifically for the application and can be handled in several different formats.
Some mobility lifts look like an opened top box. The wheelchair enters an open end of the lift over a ramp and the passenger presses a button, which raises the ramp to form a closed in box and keeps the chair from rolling out during its journey. The lift is mounted on two or three rails attached to a wall which it travels up or down according to the rider's intended destination.
These lifts are usually found in commercial buildings where the elevation change is not a full floor. Usually, the lift has controls that allow the person in the wheelchair to "call" the lift if it is at the opposite elevation.
Residential mobility lifts are often designed with an attached chair that travels up and down stairs so that elderly people don't have to exert themselves and take a chance on falling to get from one floor to another. These lifts have to be designed to fit the stair system, and can be made to go around corners as necessary.
The mobility lifts for the home are often mounted on a monorail type system that is located right above the stair treads. The chair itself folds up so that other people can use the stairs when the lift is not in operation.
As a safety feature, stair lifts have a backup battery system to power the lift when there is a power outage. Lifts also come with seat belts so the rider doesn't fall out during transit. Seats pivot so the rider can turn and put his or her feet on the level floor before standing up.
In commercial buildings or in your home, lifts are an economical way to move people who have difficulty walking up and down stairs or who can't walk at all.