Series 7
Traffic
Analysis
This series we will cover the subject of traffic analysis which has a single-point agenda of optimizing the operation of a group of elevators installed in a commercial or residential building, In the early eighties the concept of group operation had just started in India in commercial buildings.
Prior to that every elevator used to be independent in its own elevator shaft. Those days not more than two elevators used to be installed in one building, so the need for optimization was not critical. With the advent of high-rise buildings, especially commercial buildings it was important to optimize the operation and also keep the waiting time interval minimum during the peak time, so office goers reached their office in time. The group operation first started with a group of two elevators, which was called duplex operation and the third elevator was independent and worked in what was called simplex operation.
This system certainly helped, but the long queues during peak hours were a common scene in most of the office buildings in Mumbai and even other cities. This is the time which was in the early nineties, National Building Code ( NBC) came up with parameters of Traffic analysis which defined waiting time interval as the time a person has to wait for the elevator to arrive and handling capacity which was the number of persons which could be transported in 5 minutes from the lobby of the building.
Waiting for 25 seconds in the lobby was considered good, while till 45 seconds was average; beyond that was not acceptable as per NBC. This meant planning of the elevators had to be done on the drawing board and the factors which were considered were, the population of persons in the building on each floor, and to keep the waiting time interval within acceptable limits, the elevator consultant or manufacturer would help the architect in arriving at the capacity, speed, and number of elevators for the building. In the eighties and early nineties, the top manufacturers used to have 6 or max 8 car groups.
This worked well till the late nineties when the definition of high-rise building started moving skywards. The elevator operation of 25 storey building would be considered inefficient with a 6 or 8 car group.
Simultaneously, the real estate rates started going up in downtown or commercial areas, and against 80 sq.ft per person it became 50 sq.ft person; which means population to be handled at one time also increased. The problem further compounded when person whose office was on the higher floors had to stop at the lower floors and took considerable time to reach her / his destination. Many of the buildings came up with solution of allotting some lifts to lower floors and some lifts would go directly to higher floors. There would be signboards put in the lobby. This did work to some extent, however, this manual solution was still considered as inefficient and to control the movement of passengers, the presence of a lift man was essential, which reduced the car capacity.
With definition of high rise continuing to change upwards, the elevator manufacturers introduced an innovation of DESTINATION CONTROL.
In a Destination control system, there would be one elevator call button in the lobby for group of many elevators with a display panel. All that was required for a passenger was to type the floor she / he has to go to and the predesignated elevator number would be displayed. The passenger had to go and stand in front of the elevator and that elevator would take the passenger to the right floor. The waiting time interval and handling capacity would be logarithmically calculated by the controller with no manual intervention. Further, the floor buttons in the car were hidden, not allowing a passenger to change the floor when in the car. This eliminated the delay factors which would unnecessarily as be at the cost of the passengers.
