In article “Vertical Transportation Design and Traffic Calculations – Part Six”, we started
explaining how to perform the following lift
traffic design calculations:
1
Calculation of the Number of Round Trips for a Single Car,
2
Estimation of Population,
3
Calculation of the Average Number of Passengers per Trip (P),
4
Calculation of the Uppeak Handling Capacity (UPPHC),
5
Calculation of the Waiting Interval (Passenger Waiting Time),
6
Calculation of The percentage population served (%POP),
Also, in article “Vertical Transportation Design and Traffic Calculations – Part Seven”, we explained the following
two important calculations used for lift traffic design calculations:
7 Estimation
of Arrival Rate,
8
Calculation of the Round Trip Time RTT,
Today we will continue explaining the last important calculation used for lift traffic design calculations, which is the Calculation
of the quality of service for a lift system.
9
Estimation of Quality of Service (Grade of service)

There are (6) methods to
estimate the quality of service for lift systems as follows:

1
Estimation of Quality of Service based on the interval of car arrivals at the
main terminal
Table1:
Probable quality of service in office buildings
Table2: Percentage arrival rates and
uppeak intervals for different types of buildings
Important note:
Table3:
Uppeak performance  numerical values
AWT =
{0.4 + [(1.8 x P/RC)0.77]^{2}} INT
Where RC is the rated car capacity
Example#1:
A speculative, regular
10 floor (above the main terminal) building is to be built. Each floor is
1200 m2 of usable space. What is the basic specification of the lift system?
Solution:
The basic parameters
that specify any lift system are:
So, we are going to
calculate these above values.
Step#1: Estimate the
building’s population
From below table, you
can estimate the building’s population
* Patient plus three others (doctors, nurses, porters, etc.).
Above Table indicates
that 10–12 m2/person should be considered for regular office building with
multiple tenancy.
Assume 12 m2, this gives
1200/12 = 100 persons per floor.
The total population
will then be 10 floors ×100 persons per floor =1000 person.
Assume 80% daily
occupancy, ie: this gives a design population of 800.
Step#2: Estimate Arrival Rate
From below table, you
can estimate the Arrival Rate
Above Table indicates
11–15% arrival rate for regular office building with multiple tenancy; assume
12.5%.
Step#3: calculate the
required handling capacity in 5 minutes
Required handling
capacity in 5 minutes = 12.5% x 800 = 100 persons.
Step#4: Estimate Interval
Above Table in step#2
indicates an interval of 25–30 s for regular office building with multiple
tenancy. This is a speculative building so to save capital expenditure
assume 30 s.
the result:
The lift system should
be sized to be able to handle 100 persons with a 30 s interval.
Example#2:
Example#1 requires a
lift system to be sized to be able to handle 100 persons with a 30 s
interval. Design such a system and estimate the average passenger waiting
time AWT and quality of the service.
Solution:
Step#1: calculate the
Number of Round Trips over 5 minutes
If the interval is 30 s,
then a lift group must provide Number of Round Trips over 5 minutes = 5
minutes / RTT = 300 / RTT = 300 /30 = 10 trips over five minutes.
Step#2: Calculate the
Average Number of Passengers per Trip (P)
UPPHC = P x Number of
Round Trips over 5 minutes
P = UPPHC /Number of
Round Trips over 5 minutes = 100 / 10 = 10 Passengers
Step#3: Estimate Rated Car
Capacity
Step#2 means that each
car must load with 10 passengers to handle 100 persons in five minutes.
P = CC x 80/100
10 = CC x 80/100
CC = 12.5 person
A 13person lift is the
nearest standard size as per below table:
Car
loading and car capacity
Step#4: Estimate the
average passenger waiting time AWT
If a 13 person car is
used, the percentage car load = 10/13 = 77%.
From Table3 in above, a
car load of 77% indicates that AWT/INT will be 78.4%.
The estimated AWT will
be 0.784×30=23.5 s.
Step#5: Estimate the
quality of the service
Based on Table1 in
above, since The estimated AWT =23.5 s. so, the quality of service will be
very good.

2
Estimation of Quality of Service based on the performance time T
Table4:
the performance time (T) as an indicator of quality of service

3
Estimation of Quality of Service based on Average System Response
Time Performance (ASRT)
Table5:
Office Building Average System Response Time Performance

4
Estimation of Quality of Service based on Passenger Average Travel
Time to Destination (ATT)
ATT = 0.5
x UPPINT + 0.25 x UPPRTT
ATT = 0.5
x UPPINT + 0.5 x UPPRTT
RTT = 2H t_{v} + (S+1)t_{s}
+ 2P t_{p}
ATT =_{ }0.5H t_{v} + 0.5 S t_{s}
+ P t_{p}
ATT =_{ }0.5H t_{v} + 0.5 S t_{s}
+ P t_{p }+ t_{e}
The Quality of Service
based on Passenger
Average Travel Time to Destination (ATT) is estimated as per the below table:

5
Estimation of Quality of Service based on Passenger Average
Journey Time (AJT)
Thus the
passenger average journey time = the average passenger travel time (ATT) +
the average passenger waiting time (AWT).
AJT =_{ }0.5H t_{v} + 0.5 S t_{s}
+ P t_{p }+ t_{e }+ 0.5 INT_{}
AJT =_{ }0.5H t_{v} + 0.5 S t_{s}
+ P t_{p }+ t_{e }+ AWT

6
Estimation of Quality of Service based on Rule of thumb for a single lift

In the next article, we will explain step
by step the two methods for Lift Traffic design calculations with solved
examples. Please, keep following.
The previous and related articles
are listed in below table:
Subject Of Previous
Article

Article

Applicable Standards and Codes
Used In This Course,
The Need for Lifts,
The Efficient Elevator Design Solution
Parts of Elevator System Design Process
Overview of Elevator Design and
Supply Chain Process.


The
Concept of Traffic Planning,
The (4) Methods
of Traffic Design Calculations,
Principles of
Interior Building Circulation:
A Efficiency of Interior
Circulation


B Human Factors


C Circulation and Handling Capacity
Factors:
Corridor handling capacity,
Portal handling capacity,
Stairway handling capacity,
Escalator handling capacity,


Passenger Conveyors (Moving Walkways and Ramps) handling
capacity,
Lifts Handling Capacity.
D Location And Arrangement Of Transportation Facilities


Traffic design calculations:
1 Calculation of the Number of Round Trips for a Single Car,
2 Estimation of Population,
3 Calculation of the Average Number of Passengers per Trip (P),
4 Calculation of the Uppeak Handling Capacity (UPPHC),
5 Calculation of the Waiting Interval (Passenger Waiting Time),
6 Calculation of The percentage population served (%POP),


7 Estimation of Arrival Rate,
8 Calculation of the Round Trip Time RTT,

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