Vertical Transportation Design and Traffic Calculations – Part Nine


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 Formula-Based 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 Formula-Based Method (Classical Method).


Important Notes for Traffic Planning by using The Formula-Based 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 up-peak, 5-minute 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 “one-way 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 Formula-Based Method will not be used for some special conditions like:
  1. the case of multiple entrances to the building (rather than a single entrance),
  2. the case where the top speed is not attained within one floor jump (or even two or three floor jumps),
  3. the case of unequal floor heights,
  4. The case of unequal floor population,
  5. The case of combinations of above special conditions.





Now, based on The Formula-Based Method, we are going to learn how to get the most efficient and economic traffic design solution by using one of the following methods:
  1. The Conventional Design Method,
  2. The Iterative Balance Method.


  
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 handling capacity (UPPHC) of a lift system: is the total number of passengers that it can transport in a period of 5 minutes during the uppeak traffic condition with a specified average car loading.

  • Arrival rate: is the number of passengers who arrive, at the main terminal of a building, for transportation to the upper floors over the worst 5 minute period.


The results from the above rule comparison will be as follows:

Comparison
Lift Traffic Design
Not verified
non-efficient design
Verified with reasonable margin
Efficient design
Verified with too high margin
wasteful design


  • At this stage, the designer compares the calculated value of HC with the number of passengers to be moved in the peak five minutes. If HC is greater than or equal to this number of passengers, then the designer is satisfied that the system will cope with the traffic.
  • The configuration will be trimmed if the handling capacity is too large, and should it be smaller than the required value, then the designer must repeat the evaluation for more and (or) bigger and (or) faster cars.
  • However, the values calculated for RTT, INT and HC are exact only if there is a perfect match between the arrival rate and handling capacity.



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:
  • The purpose of the building,
  • The type of occupancy; single or multiple tenancy,
  • Nos. of floors,
  • Gross floor area,
  • Interfloor distance (df),
  • Attendance ratio.



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 = 75-80% 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 Table-1(in m2)

Table-1 gives the area allocated per person (in m2) for a variety of buildings based on surveys and experience of the population to be accommodated.


Building  type
Population estimate
Hotel
1.5–1.9 persons/room
Flats
1.5–1.9 persons/bedroom
Hospital
3.0 persons/bed space*
School
0.8–1.2 m2 net area/pupil
Office (multiple tenancy):
regular
10–12 m2 net area/person
prestige
15–25 m2 net area/person
Office (single tenancy):
regular
8–10 m2 net area/person
prestige
12–20 m2 net area/person
* Patient plus three others (doctors, nurses, porters, etc.).
Table-1: 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 10-20% to account for:
  • Persons working at home,
  • Persons away on holiday,
  • Persons away sick,
  • Persons away on company business,
  • Vacant posts,
  • Persons who arrive before or after the peak hour of incoming traffic,
  • Hot desking.




Step#4: Estimate Peak Arrival Rate %

Use Table-2 to estimate the peak arrival rates of many building types.

Building type
Arrival rate (%)
Interval (s)
Hotel
10-15
30-50
Flats
5-7
40-90
Hospital
8-10
30-50
School
15-25
30-50
Office( multiple tenancy)


Regular
11-15
25-30
prestige
15-17
20-25
Office( single tenancy)


Regular
15
25-30
prestige
15-17
20-25
Table-2: Percentage Arrival Rates And Up-Peak 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 Table-2 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 Table-3.

Rated load
(kg)
(RL)

Max area
(m2)
(CA)

Rated capacity
(persons)
(CC)

Actual capacity
(persons)
(AC)

Design capacity
(persons)
(DC)

Capacity factor
(%)
(CF)

Actual load
(kg)
(AL)
320
0.95
4
4.5
3.6
90
338
450
1.30
6
6.2
5.0
82
465
630
1.66
8
7.9
6.3
79
593
800
2.00
10
9.5
7.6
76
713
1000
2.40
13
11.4
9.1
70
855
1275
2.90
16
13.8
11.0
69
1035
1600
3.56
21
16.9
13.5
64
1268
1800
3.92
24
18.6
14.9
62
1395
2000
4.20
26
20.0
16.0
62
1500
2500
5.00
33
23.8
19.0
58
1785
Table-3: 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 Table-4, assign the car load % from step#11 and find its related AWT/INT %.

Car load (%)
AWT/INT (%)
Car load (%)
AWT/INT (%)
30
0.32
75
0.74
40
0.35
80
0.85
50
0.40
85
1.01
60
0.50
90
1.30
70
0.65
95
1.65

Table-4: 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 Table-6, assign the CC column and the Nos. of floors row, the intersection will give H and S values.


Table-6: 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 Table-7:

building
The interfloor distance (df)
Domestic dwellings
around 3.0m per floor
commercial buildings
from 3.3 m to 3.6 m upwards
Table-7: 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 Table-8, assign the total lift travel value from step#16 and select the related rated speed.

Lift travel
(m)
Rated speed
(m/s)
Acceleration
(m/s2)
Single floor flight time
(s)
<20
<1.00
0.4
10.0
20
1.00
0.4-O.7
7.0
32
1.60
0.7-0.8
6.0
50
2.50
0.8-0.9
5.5
63
3.00
1.0
5.0
100
5.00
1.2
4,5
120
6,00
1.2
4.5
>120
>6.00
1.2
4.5
Table-8: 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 Table-8 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 Table-9, assign the related Door opening time (to) and Door closing time (tc) based on the door operator, type and opening.

Door
type

Closing and opening times (s) for stated door width (m)

Closing
Opening (normal)
Opening (advanced)
0.8
1.1
0.8
1.1
0.8
1.1
Side
3.0
4.0
2.5
3.0
1.0
1.5
Centre
2.0
3.0
2.0
2.5
0.5
0.8

Table-9: 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 Table-10 based on the current design condition.

Condition
Passenger transfer time (tp) in seconds
If the car door width is 1.0m or less
1.2
If door widths of 1.0m and above
1.2
If passengers have no reason to rush or are elderly
2
residential buildings (as per ISO 4190/6)
1.75
Table-10: 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 tv + (S+1)ts + 2P tp

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 tv + (S+1)ts + 2P tp + 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:

Comparison
Lift Traffic Design
Not verified
Non-efficient design and the designer must repeat the evaluation for more and (or) bigger and (or) faster cars.

Verified with reasonable margin
Efficient design 
Verified with too high margin
Wasteful design and the designer must repeat the evaluation for more and (or) bigger and (or) faster cars.



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 Table-11, assign the related quality of service for the designed interval (INT).


Interval (s)
Quality of service
≤20
Excellent
25
Very good
30
Good
40
Poor
≥ 50
Unsatisfactory

Table-11: 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 Table-12 to assign the related quality of service for the calculated performance time T from step# 22.

Value of T (s)
Quality Of Service For The Lift System
8.0-9.0
Excellent system
9.0-10.0
Good system
10.0-11.0
Average system
11.0-12.0
Poor system
>12.0
Consider system replacement

Table-12: 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 tv + 0.5 S ts + P tp

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:

Time
Aim for
Poor
ATT
<60s
>70s


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 tv + 0.5 S ts + P tp + 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:

Time
Aim for
Poor
AJT
<80s
>90s



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 Table-1: Estimation Of Population for regular office building
10-12 m2/person
The estimated population = the usable area of the building from step#1 / the area allocated per person  from Table-1(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 Table-2, estimate the peak arrival rates for regular office building
peak Arrival Rate % = 11-15%
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 Table-2 to estimate the Interval of car arrivals at the main terminal
So, the Interval of car arrivals at the main terminal = 25-30 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 Table-3. 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 Table-4, 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 Table-6, 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 Table-8, 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 Table-8 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 Table-9, 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 Table-9 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 tv + (S+1)ts + 2P tp = 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 Table-11, 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 Table-12 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 tv + 0.5 S ts + P tp = 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 tv + 0.5 S ts + P tp + 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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