Today we will explain
step by step the two methods for Lift Traffic design calculations with solved
examples.
Methods for Lift Traffic Design
Calculations

In article “Vertical Transportation Design and Traffic Calculations – Part Two”, we indicated that There are (4) methods used for the traffic
design and analysis as follows:
First: Calculation
methods, which includes:
1 The FormulaBased
Method (Classical Method),
2 The Monte Carlo
Simulation Method.
Second: Simulation
methods, which includes:
3 Discrete Event
Simulation Method,
4 Time Slice Simulation
Method.
Also, we indicated that
In this course, we will explain only the first method which is The
FormulaBased Method (Classical Method).
Important
Notes for Traffic Planning by using The FormulaBased Method (Classical
Method)
A The traffic analysis
and design calculation in this course is mainly relevant to commercial office
buildings.
B The conventional
design assumes the arrival of passengers at constant intervals served by
lifts arriving at constant intervals but In practice passengers do not
conveniently arrive in batches equal to 80% of the rated car capacity and
they don’t register the same number of destinations during each trip.
C The traffic period
for evaluation when sizing an office building is usually a morning uppeak,
5minute segment. During this period of time, little or no traffic is moving
interfloor or down in the building. The lifts are loading passengers at the
main lobby, distributing those passengers to various upper floors and then
making an express trip back to the main lobby for the next load. Therefore,
studies are based upon “oneway traffic” in the up direction with no stops at
the intervening floors in the down direction. It is possible to consider some
down travelling passengers, but there is no consensus as to how big this flow
should be. uppeak traffic flow is the best method which can be used to
compare any designers results.
D In general, if the
uppeak traffic pattern is sized correctly all other traffic patterns will
also be adequately served. There are exceptions to this comment. For example:
in hotels at meal times; in hospitals at visiting times; in buildings with
trading floors (insurance and stock markets), which open at specified times
and at lunch time in all buildings.
E Many of the
recommendations are based on empirical data acquired by observation and the
experience gained in their application.
F It is important to
remember that the distribution and size of the population of any large
building changes regularly. Thus a design which is tightly planned may prove
inadequate once a building has been occupied for a year or two. To understand
the effect of these changes on a design, it is essential to document the
criteria and decisions taken at all stages of a design.
G It is important that
the architect or planner establishes the lift system required at a very early
stage and not after the rest of the building has been designed, as has often
happened in the past.
H The FormulaBased Method will not be used for some special conditions like:

Now, based on The FormulaBased Method,
we are
going to learn how to get the most efficient and economic traffic design
solution by using one of the following methods:

First
Method: The Conventional Design Method

The conventional
procedure used in the traffic design of lift systems is to determine the
handling capacity for the uppeak traffic situation and compare it with the
arrival rate, the result must verify the following:
The designed handling capacity of the lift
system over 5 minutes ≥ the arrival rate at morning 5 minutes uppeak period
Where:
The results
from the above rule comparison will be as follows:

Step By
Step Design Of Lift Systems By Using
The Conventional Design
Method

First:
Given data

For Using the
conventional design method, Usually
the given data will be:

Second: Calculated / Estimated Data

Step#1: Estimate
The Usable Area of The Building
Use the
following rule to estimate the usable area of the building:
Usable
area =75–80% of gross area
Or, If the rentable area
is given, so:
Usable
area=80–85% of rentable area
Note:
if the net gross area is given per floor, then:
Usable
area for the whole building = Usable area per floor x nos. of floors = 7580%
of gross area per floor x nos. of floors

Step#2: Estimate
The Building’s Population
Use the following rule
to estimate The Building’s Population:
The
estimated population = the usable area of the building from step#1 / the area
allocated per person from Table1(in
m2)
Table1 gives the area
allocated per person (in m2) for a variety of buildings based on
surveys and experience of the population to be accommodated.
* Patient plus three others (doctors, nurses, porters, etc.).
Table1: Estimation
Of Population

Step#3: Calculate The Total Daily Population Based On The Attendance
Ratio
Use the following rule
to Calculate The Total Daily Population Based
On The Attendance Ratio:
Total daily population = the building’s population from step#2 x given attendance
ratio
Notes:
If the attendance ratio
is not given, estimate it as 80 – 90%.
Why we use the
attendance ratio?
In many buildings it is unlikely that all the total population
is present on any day. Thus, in design calculations, the total building
population can be reduced by 1020% to account for:

Step#4: Estimate Peak Arrival Rate %
Use Table2 to estimate the peak arrival rates of many building
types.
Table2: Percentage Arrival Rates And
UpPeak Intervals

Step#5: Calculate
The Required Handling Capacity in 5 Minutes
Use the following rule to calculate the required handling capacity in
5 minutes:
the
required handling capacity in 5 minutes = peak Arrival Rate % from step#4 x Total
daily population from step#3

Step#6: Estimate Interval Of Car
Arrivals At The Main Terminal
Use Table2 in above to estimate the
Interval of car arrivals at the main terminal.
Note:
Usually take the higher value to save the capital expenditure
of the building.

Step#7: Calculate
The Number Of Round Trips Over 5 Minutes
Use the following rule to calculate The Number Of Round Trips Over 5
Minutes:
the
Number of Round Trips over 5 minutes =
5 minutes / Interval from step#6 = 300 /
Interval from step#6

Step#8: Calculate
the Average Number of Passengers per Trip (P)
Use the following rule to calculate the Average Number of Passengers
per Trip (P):
the
Average Number of Passengers per Trip (P)= the required handling capacity in
5 minutes from step#5 /Number of Round Trips over 5 minutes from step#7

Step#9: Calculate
The Car Capacity Of The Lift (CC)
Use the
following rule to calculate The Car Capacity Of The Lift (CC):
the car capacity of the lifts (CC) = P x 100/80

Step#10: Select The
Nearest Standard Car Capacity
Select
the rated standard car capacity (CC) from Table3.
Table3:
Car loading and car capacity
Note:
Rated Car Capacity (CC)
calculated by dividing the value for Rated Load RL by 75 as EN81, Clause
8.2.3.

Step#11: Calculate
The Car Load %
Use the following rule to
calculate The Car Load %:
the car
load % = the car capacity from step#9
x 100 / standard rated car capacity from step#10

Step#12:
Estimate The Average Passenger Waiting Time AWT
From Table4, assign the
car load % from step#11 and find its related AWT/INT %.
Table4:
Uppeak performance  numerical values
Then ,
the
average passenger waiting time AWT =
AWT/INT % x interval from step#6

Step#13: Calculate
the Number of Passengers per Trip P based on the nearest standard car
capacity from step#10
Use the following rule
to calculate the Number of Passengers per Trip P:
P = CC x
80/100

Step#14: Estimate
The Average Highest Reversal Floor (H) And Expected Number Of Stops (S)
From Table6, assign the CC column and the Nos. of floors row, the
intersection will give H and S values.
Table6:
Values of H and S for rated capacity

Step#15: Estimate
the Interfloor distance (df) if it is
not given
If the Interfloor
distance (df) is not given, select it based on Table7:
Table7: Interfloor distance (df)
Commercial buildings often introduce a mixed floor pitch, It is
recommended that an average floor height be assumed and that any
irregularities are dealt with separately.

Step#16:
Calculate Total Lift Travel
Use the following rule to calculate Total Lift Travel:
Total
Lift Travel = nos. of floors x interfloor distance (df)

Step#17: Estimate Rated Speed (V)
From Table8, assign the total lift travel value from step#16 and
select the related rated speed.
Table8: Typical lift dynamics

Step#18: Calculate
Single Floor Transit Time (tv)
Use the following rule
to calculate Single Floor Transit Time (tv):
Single Floor Transit Time (tv) = interfloor distance (df) from step#15 / Rated Speed V from step#17

Step#19:
Estimate Single Floor Flight Time tf(1)
From Table8 in above, assign the related single floor flight
time tf(1) with the total lift travel from step#16.

Step#20: Estimate Door opening time (to) and Door
closing time (tc)
From Table9, assign the related Door opening time (to) and Door closing time (tc) based on the door operator, type and
opening.
Table9: Door Operating Times

Step#21: Calculate Door Operating Time (td)
Use the following rule
to calculate Door Operating Time (td):
Door Operating Time (td) = Door opening time
(to) from step#20 + Door closing time (tc) from step#20

Step#22: Calculate The Performance Time (T)
Use the following rule
to calculate The Performance Time (T):
Performance Time (T) = door operating time
(td) from step#21 + single floor flight time
tf(1) from step#19

Step#23: Calculate Time Consumed When Stopping (ts)
Use the following rule
to calculate Time Consumed When Stopping (ts):
Time consumed when stopping (ts) = performance time (T) from
step#22
Single Floor Transit Time (tv) from step#18

Step#24:
Estimate Passenger Transfer Time (tp)
Select the passenger transfer time (tp) from the Table10 based
on the current design condition.
Table10: Passenger Transfer Time (tp)

Step#25: Calculate The Round Trip
Time (RTT)
Use the following rule
to calculate the round trip time (RTT):
The Round
Trip Time (RTT) = 2H t_{v} + (S+1)t_{s}
+ 2P t_{p}
where:
H: the average highest
reversal floor from step#14,
tv: Single Floor Transit Time from step#18,
S: expected number of
stops from step#14,
ts: Time consumed when stopping from step#23,
P: the Number of
Passengers per Trip from step#13,
tp: Passenger transfer time from step#24.
Note:
Where a lift is serving a set of floors or zone in a building,
which is not adjacent to the main terminal, an extra time to make the jump
to/from the express zone must be added to the above RTT equation as follows:
RTT = 2H t_{v} + (S+1)t_{s}
+ 2P t_{p} + 2He tv
Where He is the number of average height
floors passed through to reach the first served floor of the express zone.

Step#26: Calculate The Nos. Of
Lifts (L)
Use the following rule
to calculate nos. of lifts (L):
Nos. Of
Lifts (L) = RTT from step#25 / interval from step#6
Note:
Round
the result to nearest integer.

Step#27:
Calculate The designed Interval (INT)
Use the following rule
to calculate The Actual Interval (INT):
Actual
Interval (INT) = RTT from step#25 / L from step#26

Step#28: Calculate
The designed Handling Capacity (HC) over 5 minutes
Use the following rule
to calculate The Actual Handling Capacity (HC):
The
Actual Handling Capacity (HC) = P x L x 300/RTT
where:
P: the Number of
Passengers per Trip from step#13,
L: Nos. Of Lifts from
step#26,
RTT: the Round Trip Time from step#25.

Step#29: Calculate of The Percentage Population Served (%POP)
Use the following rule
to calculate The Percentage Population Served (%POP):
The Percentage Population Served (%POP) =
UPPHC from step#28 x 100 / total daily population from step#3

Step#30:
Check The Efficiency Of The Lift System
Compare
between The actual handling capacity of the lift system from step#28 and the
arrival rate at morning 5 minutes uppeak period from step#5, and verify that:
The
designed handling capacity of the lift system over 5 minutes from step#28 ≥
the arrival rate at morning 5 minutes uppeak period from step#5
The results
from the above rule comparison will be as follows:

Step#31:
Check The Quality Of The Service (Grade Of Service)
We have many options for checking The
Quality Of The Service (Grade Of Service) as follows:
Option#1: Check the quality of the service based
on Based on The designed interval (INT)
By using Table11, assign
the related quality of service for the designed interval (INT).
Table11:
Probable quality of service in office buildings
Option#2: Check the Quality of Service based
on the performance time T
For a 3.3 m interfloor
height use Table12 to assign the related quality of service for the
calculated performance time T from step# 22.
Table12:
the performance time (T) as an indicator of quality of service
Option#3: Check the Quality of Service based
on Passenger
Average Travel Time to Destination (ATT)
Use the following rule
of thumb to check the Quality of Service based on Passenger Average Travel Time to Destination
(ATT):
ATT = 0.5
x UPPINT from step#27 + 0.5 x UPPRTT from step#25
But for A more accurate estimate use the below
rule of thumb:
ATT =_{ }0.5H t_{v} + 0.5 S t_{s}
+ P t_{p}
Where:
H: the average highest
reversal floor from step#14,
tv: Single Floor Transit Time from step#18,
S: expected number of
stops from step#14,
ts: Time consumed when stopping from step#23,
P: the Number of
Passengers per Trip from step#13,
tp: Passenger transfer time from step#24.
Then, The Quality of
Service based on Passenger Average Travel Time to Destination (ATT) is estimated as
per the below table:
Option#4: Check the Quality
of Service based on Passenger Average Journey Time (AJT)
Use the following rule of thumb to Check the Quality
of Service based on Passenger Average Journey Time (AJT):
AJT =_{ }0.5H t_{v} + 0.5 S t_{s}
+ P t_{p }+ 0.5 INT
Where:
H: the average highest
reversal floor from step#14,
tv: Single Floor Transit Time from step#18,
S: expected number of
stops from step#14,
ts: Time consumed when stopping from step#23,
P: the Number of
Passengers per Trip from step#13,
tp: Passenger transfer time from step#24,
INT: the designed interval (INT) from step#27.
Then, The Quality of
Service based on Passenger Average Journey Time (AJT) is estimated as per the below
table:

Summary of
Steps for Design Of Lift Systems By Using
The Conventional Design
Method

Step #

Step Description

1

Estimate the usable area
of the building

2

Estimate the building’s
population

3

Calculate the total daily population based on the attendance
ratio

4

Estimate peak Arrival Rate %

5

calculate the required
handling capacity in 5 minutes

6

Estimate Interval of car arrivals at the main terminal

7

calculate the Number of Round Trips over 5 minutes

8

Calculate the Average
Number of Passengers per Trip (P)

9

Calculate the car
capacity of the lift (CC)

10

Select the nearest
standard car capacity

11

Calculate the car load %

12

Estimate the average
passenger waiting time AWT

13

Calculate the Number of
Passengers per Trip P based on the nearest standard car capacity from step#10

14

Estimate the average
highest reversal floor (H) and expected number of stops (S)

15

Estimate the Interfloor distance (df) if it is
not given

16

Calculate total
lift travel

17

Estimate Rated Speed (V)

18

calculate Single Floor Transit Time (tv)

19

Estimate single floor flight time tf(1)

20

Estimate Door opening time (to) and Door closing time (tc)

21

Calculate door operating time (td)

22

Calculate the performance time (T)

23

Calculate Time consumed when stopping (ts)

24

Estimate Passenger transfer time (tp)

25

Calculate the round trip
time (RTT),

26

calculate the nos. of
lifts (L)

27

Calculate the designed
interval (INT)

28

Calculate the designed
handling capacity (HC) over 5 minutes

29

Calculate of The percentage population served (%POP)

30

Check the efficiency of
the lift system

31

Check the quality of the
service (grade of service)

Example#1:
Design a lift system for a speculative,
regular office building having ten floors above the main terminal. Each floor
has 1500 m2 of net space. Assume an interfloor distance of 3.3 m.
Solution:
Step #

Step Description

1

Estimate the usable area
of the building
Usable area per floor =75–80%
of gross area = 80% x 1500 m2 = 1200 m2 per floor
Usable area for the
whole building = Usable area per floor x nos. of floors
= 1200 m2 x 10 = 12000 m2

2

Estimate the building’s
population
from Table1: Estimation
Of Population for regular office building
1012 m2/person
The estimated population
= the usable area of the building from step#1 / the area allocated per
person from Table1(in m2) = 12000 /
12 = 1000 person

3

Calculate the total daily population based on the attendance
ratio
the attendance ratio is not given, take it 80%
Total daily population = the building’s
population from step#2 x given attendance ratio = 1000 person x 80% = 800
person

4

Estimate peak Arrival Rate %
From Table2, estimate the peak arrival
rates for regular
office building
peak Arrival Rate % = 1115%
So, assume average value
for peak Arrival Rate % = 12.5%.

5

Calculate the required
handling capacity in 5 minutes
the required handling capacity in 5 minutes = peak Arrival Rate % from step#4 x Total daily population from
step#3 = 12.5% x 800 = 100 person

6

Estimate Interval of car arrivals at the main terminal
Use Table2 to estimate the Interval of car arrivals at the
main terminal
So, the Interval of car arrivals at the main terminal = 2530
seconds
Usually take the higher
value to
save the capital expenditure of the building.
Then, Interval of car arrivals at the main terminal = 30 seconds

7

Calculate the Number of Round Trips over 5 minutes
the Number of Round Trips over 5 minutes = 5 minutes / Interval from step#6 = 300 / Interval from step#6 = 300/30 = 10

8

Calculate the Average
Number of Passengers per Trip (P)
the Average Number of
Passengers per Trip (P)= the required handling capacity in 5 minutes from
step#5 /Number of Round Trips over 5 minutes from step#7 = 100 person / 10 =
10 person

9

Calculate the car
capacity of the lift (CC)
the car capacity of the
lifts (CC) = P x 100/80 = 10 x 100/80 = 12.5 person

10

Select the nearest
standard car capacity
Select the rated
standard car capacity (CC) from Table3. So, the rated standard car capacity
(CC) = 13 person

11

Calculate the car load %
the car load % = the car capacity
from step#9 x 100 / standard rated car capacity from step#10 = 12.5 x
100 / 13 = 96.2%

12

Estimate the average
passenger waiting time AWT
From Table4, assign the
car load % from step#11 and find its related AWT/INT %.
For car load % = 96.2 %
, the related AWT/INT % = 1.65
So, the average
passenger waiting time AWT = 1.65 x 30 = 49.5 seconds

13

Calculate the Number of
Passengers per Trip P based on the nearest standard car capacity from step#10
P = CC x 80/100 = 13 x
80 / 100 = 10.4 person

14

Estimate the average
highest reversal floor (H) and expected number of stops (S)
From
Table6, assign the CC column and the Nos. of floors row, the intersection
will give H and S values.
For 10
nos. of floors and CC = 13 person:
H= 9.5, S = 6.7

15

Estimate the Interfloor distance (df) if it is not given
interfloor distance is given = 3.3 m

16

Calculate
total lift travel
Total Lift
Travel = nos. of floors x interfloor distance (df) =
10 x 3.3 m = 33 m

17

Estimate Rated Speed (V)
From Table8, assign the total lift travel value from step#16
and select the related rated speed.
For total lift travel = 33 m, the related rated speed = 1.6 m/s

18

Calculate Single Floor Transit Time (tv)
Single Floor Transit Time (tv) =
interfloor
distance (df) from step#15 / Rated Speed V from
step#17 = 3.3 / 1.6 = 2.1 second

19

Estimate single floor flight time tf(1)
From Table8 in above, assign the related single floor flight
time tf(1) with the total lift travel from step#16.
For total lift travel = 33 m, the related single floor flight time tf(1)
= 6 seconds

20

Estimate Door opening time (to) and Door closing
time (tc)
From Table9, assign the related Door opening time (to) and Door closing time (tc) based on the door operator, type and
opening.
Select center opening doors, advanced opening and
car width 1.1 meter gives
to = 0.8 second & tc = 3 seconds

21

Calculate door operating time (td)
Door Operating Time (td) = Door opening time (to) from step#20 +
Door closing
time (tc) from step#20 = 0.8 + 3 = 3.8 seconds

22

Calculate the performance time (T)
Performance Time (T) = door operating time (td) from step#21 +
single floor flight time tf(1) from
step#19 = 3.8 + 6 = 9.8 seconds

23

Calculate Time consumed when stopping (ts)
Time consumed when stopping (ts) = performance
time (T) from step#22 Single Floor Transit Time (tv) from step#18 = 9.8  2.1 = 7.7
seconds

24

Estimate Passenger transfer time (tp)
Select the passenger transfer time (tp) from the Table9 based
on the current design condition.
For car door width above 1 meter. tp = 1.2 seconds

25

Calculate the round trip
time (RTT),
The Round Trip Time
(RTT) = 2H t_{v} + (S+1)t_{s} + 2P
t_{p }= 2 (9.5) 2.1 + (6.7+1) (7.7) + 2 (10.4) 1.2 = 124.2 seconds
where:
H: the average highest
reversal floor from step#14,
tv: Single Floor Transit Time from step#18,
S: expected number of
stops from step#14,
ts: Time consumed when stopping from step#23,
P: the Number of
Passengers per Trip from step#13,
tp: Passenger transfer time from step#24.

26

Calculate the nos. of
lifts (L)
Nos. Of Lifts (L) = RTT
from step#25 / interval from step#6 = 124.2 / 30 = 4.14
Round the result to
nearest integer, then Nos. Of Lifts (L) = 4

27

Calculate the designed
interval (INT)
Actual Interval (INT) =
RTT from step#25 / L from step#26 = 124.2 / 4 = 31.05 seconds

28

Calculate the designed
handling capacity (HC) over 5 minutes
The Actual Handling
Capacity (HC) = P x L x 300/RTT = 10.4 x 4 x 300 / 124.2 = 100.48 person
where:
P: the Number of
Passengers per Trip from step#13,
L: Nos. Of Lifts from
step#26,
RTT: the Round Trip Time from step#25.

29

Calculate of The percentage population served (%POP)
The Percentage Population Served (%POP) = UPPHC from step#28 x
100 / total daily population from step#3 = 100.48 x 100 / 800 = 12.56%

30

Check the efficiency of
the lift system
The designed
handling capacity of the lift system over 5 minutes from step#28 ≥ the
arrival rate at morning 5 minutes uppeak period from step#5
Since 100.48 ≥ 100 with
reasonable margin, so the design is efficient.

31

Check the quality of the
service (grade of service)
Option#1: Check the quality of the service based on Based on The designed interval (INT)
By using Table11, assign
the related quality of service for the designed interval (INT) from step#27.
For the designed
interval (INT) = 31.05 seconds, the quality of the
service is good.
Option#2: Check the Quality of Service based
on the performance time T
Use Table12 to assign
the related quality of service for the calculated performance time T from
step# 22.
For performance time T =
9.8 seconds, the quality of the service is good.
Option#3: Check the Quality of Service based
on Passenger
Average Travel Time to Destination (ATT)
ATT =_{ }0.5H t_{v} + 0.5 S t_{s}
+ P t_{p}^{ }= 0.5 (9.5) 2.1 + 0.5 (6.7) 7.7 + 10.4 (1.2) =
9.975+25.795+12.48 = 48.25 seconds
Where:
H: the average highest
reversal floor from step#14,
tv: Single Floor Transit Time from step#18,
S: expected number of
stops from step#14,
ts: Time consumed when stopping from step#23,
P: the Number of
Passengers per Trip from step#13,
tp: Passenger transfer time from step#24.
Since ATT <60s, the quality of the service is good.
Option#4: Check the Quality of Service based
on Passenger
Average Journey Time (AJT)
AJT =_{ }0.5H t_{v} + 0.5 S t_{s}
+ P t_{p }+ 0.5INT = 0.5 (9.5) 2.1 + 0.5 (6.7) 7.7 + 10.4 (1.2) + 0.5
(31.05) = 9.975+25.795+12.48+15.525 = 63.775 seconds
Where:
H: the average highest
reversal floor from step#14,
tv: Single Floor Transit Time from step#18,
S: expected number of
stops from step#14,
ts: Time consumed when stopping from step#23,
P: the Number of
Passengers per Trip from step#13,
tp: Passenger transfer time from step#24,
INT: the designed interval (INT) from step#27.
Since AJT <80s, the quality of the service is good.

In the next article, we will explain step
by step The Iterative Balance Method 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,


9 Calculation of the quality of service (Grade of
Service)

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