What keeps you in place when you are travelling in escalator ?

An escalator is vertical transportation device basically a conveyor belt with steps carries people between floors of a building.Escalators have the capacity to move a large number of people, and they can be placed in the same physical space as a staircase and they have no waiting interval.It has two wheels at each end that drive a set of chains in a pulley-like fashion. 

The steps also have two sets of wheels that move along their own inner tracks and are positioned in such a way that each step is always level which is especially important when someone is getting on or off a moving escalator. 

Obviously, gravity is exerting a constant force on you; however, the force the escalator exerts as it moves you up or down perfectly counteracts gravity keeping you in place on the step.The moving sidewalk complete with handrails and other safety devices is a horizontal version of the escalator.