Periodic direction reversal of escalators will reduce the wear on the chains, gears and sprockets in an escalator or moving walk over a long period of time, as the amount wear is spread out and equalised among the various friction and wear points. Changing direction of the escalator thus helps to extend the lifespan of these components and may reduce lifecycle replacement costs. However, this may not always be true in all situations.
Owners of escalators and moving walks may sometimes decide to change the direction of travel of their equipment, for reasons such as altering the passenger flow in malls to maximize exposure to retail outlets, or when an escalator undergoes major repair, modernization or replacement works, and the adjacent escalators have to accommodate the change in traffic load.
While escalators and moving walks can reverse their direction, and it would seem like a good measure to do so, it is not a common practice. The design of the area or building where the escalator or moving walk is located in and the flow of human traffic also determine whether a direction reversal is suitable. For example, it would not be suitable to reverse the direction of travel in an airport where the escalator or moving walk is serving an arrival or departure terminal, or when the equipment crosses security zones.
In some situations, direction reversal can create unnecessary safety risks where passenger guidance and safety spaces around the escalators or moving walks are unfavourable. This is especially so when an escalator is suddenly made to move many passengers from an open area to a narrow area, as this promotes overcrowding at the exit landing and will lead to an unsafe condition. A proper traffic flow analysis should always be incorporated into the design of a system of escalators or moving walks to avoid such situations. In addition, aspects such as signage and way-finding are extremely important to consider and modify where needed, to suit the reversed situation – especially with Adjacent Criss-Cross lay-outs.
Yet in some cases direction reversal favours the flow of traffic. For example, escalators in stadiums would run in one direction to facilitate spectators going into the building before an event begins, and then run in the reverse direction after the event ends to expedite the flow of people out of the building. Other examples are cinemas, theatres, or in Mass Rapid Transport systems (MRT).
If an escalator or moving walk is expected to change its direction periodically, however, it should be scheduled to do so from the moment the escalator is put into commission, and this schedule of reversing directions at one to two month intervals (or ideally shorter) must be continued throughout the life time of the equipment.
If an escalator or moving walk has been running in one direction for a long period of time, it should NOT be made to suddenly operate in the opposite direction. When escalators have been running in the same direction for a prolonged period, the wear and tear patterns of the various parts and components become pronounced as a result of continuously running in the same direction. There will be different wear points, and the catenaries in the chains, sprockets and handrails will have changed. Suddenly changing direction may lead to a mis-match on the sprockets, chains, rails and steps alignment, and this can cause major damage, such as step-crash, dislodgement of the step chain, or the chain ‘jumping out’ of the sprocket. Also, when suddenly reversing an escalator after a long period of running in the same direction, it will tend to produce a much higher amount of noise.
Hence, if a direction change is necessary after prolonged use in one direction, a thorough inspection must first be carried out, to assess the parts that must be replaced (such as sprockets, step chains, guides etc), and several functional and safety tests must be conducted, to verify that all the safety switches and sensors will still work as intended.
By understanding the characteristics of wear in an escalator or moving walk and the impact on passenger traffic and safety, direction reversal can be a useful tool for owners to prolong the service of their equipment, and to reduce running costs. However, careful consideration should be taken, related to the available space and flow patterns, the signage and way-finding, and most importantly the safe operation of the escalator, before doing so.