Departure Delays in Lift Systems

There is a range of lift systems with more than one car or cabin per shaft. Double deck lifts have a car with two attached cabins, serving adjacent floors at the same time. Other systems enable two independent cars to share the same shaft. The next generation ropeless lifts will allow many cars to share the same shafts. In these systems, the interaction between the cars and cabins affect the quality of service for passengers. Departure delays occur when passenger loading and unloading times or the sequence of stops required to serve passengers is not the same. The consequence is that cars and cabins delay each other’s departure. Departure delays can also occur in lift systems with a single car and cabin per shaft, for example, when destination calls are registered at a significant walking distance from the lift lobby. To include departure delay in an assessment of quality of service, definitions of passenger and cabin departure delays, and a method to measure these delays are required. This paper describes the different types of departure delays and their causes. This provides metrics which can be applied in lift planning and dispatcher design.