## Why am I getting low or zero results when using the General Analysis or Enhanced Up Peak calculations?

Your "low results" are a due to a known limitation of round trip time calculations. The Elevate manual (Results section) says:

Low and Zero Results: Round Trip Time calculations are intended for analysis of peak traffic, when the elevators are busy. If this is not the case, some results may be low, or even zero. This is a limitation of the calculation. With Elevate, you can overcome this by changing the Analysis type to Simulation."

Consider a round trip when there are a group of people.  In this instance the elevator stops 5 times, and the round trip time is 170 seconds.

If we have less people, then the elevator will stop less times in a typical round trip:

Even:

The whole basis for the round trip time calculation begins to break down:

The calculation breaks down, because there is just not enough traffic for the system you are analyzing.  Round Trip Calculations cannot work effectively at low levels of traffic, as the mathematical derivation is based on the assumption that the elevators are constantly cycling around the building, and that there are queues of people waiting for them when they arrive at the main terminal.

Where Round Trip Time calculations break down, simulation can be applied.

### But I get a sensible results with slower speeds/less cars, etc. .... I have not changed the traffic, but for the calculation I am interested in it doesn't work!

The point at which the RTT "breaks down" is related to both how much traffic there is and the specification of a system.

If you have an 8 car group, then you will need a lot more traffic to make the round trip calculation meaningful than if you have a 2 car group.

For example:  your round trip time calculation is meaningful when you use a 1.0 m/s lift - the lifts are taking a long time to go round the building; so there are more people waiting when the lifts gets back to ground.  When you increase the specification to 1.6 m/s then the round trip time is faster; in the calculations this has a similar effect to increasing the number of lifts or reducing the amount of traffic. You have now reached the point at which the calculation breaks down. The assumptions of the calculation are no longer valid.

If you switch to the "old fashioned" up peak calculation you may see that the 1.6 m/s system has a handling capacity of say  40%, where as you are running it at 15%.  So it is hardly working at all - and likely to be close to the point where the basic assumptions of the RTT calculation break down. However, if you ran the system at 40% then the interval would be unacceptably high, around 50s.  And unrealistic as the traffic would not actually reach this level.

If you want to stay with RTT calculations rather than use simulation, any way you can use to make the RTT worse will help you towards getting the calculation back into its working range for the 1.6 m/s solution. E.g. you could increase the traffic marginally (e.g. to 17%).