Where possible, stairs and escalators should not lead directly off corridors, but should be accessed from landing and lobby areas, where people may wait without obstructing a circulation route. Thus the
vertical and horizontal modes of circulation can be allowed to merge smoothly.
If it is the intention to encourage the use of stairs for short journeys to/from adjacent floors (interfloor movement), then the stairs should be clearly visible, adequately signed and reached before entering the lift lobby.
The location of escalators should observe the same recommendations as those for the location of stairways. However, it should be noted that escalators occupy a larger footprint than stairs in order to accommodate their inclination, structure and equipment spaces. It is particularly important that the boarding and alighting areas adjacent to an escalator are not part of another circulation route. This will provide a safe area for passengers to board and alight. This topic is discussed further in Chapter 3. Escalators are typically used for short range movement between adjacent floors (the deep underground railway systems excepted). They are found in offices between principal levels, in shops between trading floors, in shopping centres between malls and elsewhere, such as railway stations, hospitals, museums, etc. They are usually sited in an obvious circulation path making it easy for pedestrians to board them. There are several standard escalator arrangements, as shown in Figure 1.10. Type (c) is typical of a shop as it allows the shop to deliberately lengthen the circulation route to pass goods for sale. This configuration also takes up less space.
1.4.3 Lifts
Lifts should always be placed together whenever possible, rather than distributed around a building. This arrangement will help to provide a better service (shorter intervals), mitigate the failure of one car (availability of an adjacent car or cars) and lead to improved traffic control (group systems).
Lift lobbies should preferably not be part of a through circulation route, either to other lifts, or other areas in the building. Lobbies should be provided that are dedicated to passengers waiting for the lifts. Eight lifts are the maximum number which it is considered possible to present to waiting passengers, especially if the lifts are large (<16 person). This constraint allows passengers to ascertain the arrival of a lift easily (from the landing lantern and gong signals), walk across the lobby and enter the lift before the doors start to close.
The distance across a lobby is important. If the lobby is too large, passengers have too far to walk and the closure of the car doors has to be delayed (increasing the lobby door dwell time) to accommodate the increased walking time. BSISO4190–1:1999 gives some guidance. For residential buildings, the landing depth (measured in the same direction as the depth of the car) should be at least equal to the depth (d1) of the deepest car. For office buildings, where lifts are located side by side, the landing should be at least equal to 1.5×d1 and not less than 2.4 m. In office buildings, where lifts are arranged face to face, the distance between facing walls should be at least equal to the sum of the depths of two facing cars, but not more than 4.5 m.
The ideal lobby size would be one which could accommodate one full car load of passengers waiting and permit the simultaneous disembarkation of one full car load of arriving passengers. This area can be calculated from the information given in Section 1.2.2.
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Figure 1.10 Escalator configurations (a) parallel (b) cross-over (c) walk round
Figure 1.11 Preferred arrangement for lift cars: side by side (or in line)
Figure 1.12 Preferred arrangement for lift cars: facing
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The preferred arrangements from BS5655: Part 6:2002 of two to four lifts arranged side by side are given in Figure 1.11 and for two to eight lifts arranged opposite each other are shown in Figure 1.12. Note all the lobbies, indicated (L), have separate waiting areas with no through circulation.
Example 1.3
Suppose there are four 21 person lifts arranged in a facing (2×2) configuration. What distance across the lobby would be appropriate given the car width is 2100 mm and the car depth is 1600 mm? The cars occupy a 6.0 m length of lobby (along the front of the cars). Assume the persons waiting do so at the dense level of occupancy. Assume that a 21 person car can accommodate 21 persons.
When one of the cars in the group of four arrives, it will disembark 21 persons. Thus for these
passengers to be accommodated at the dense level of occupancy of 2.0 persons/m2 (see Table 1.1 and Figure 1.2) in the lobby, an area of 10.5 m2 would be required. If it is assumed that there are 21
persons waiting to board, then they will require a further area of 10.5 m2. Hence a total of 21 m2 is required. As the lobby length is 6.0 m, then a width of 3.5 m is indicated, which is slightly larger than the ISO recommendation of the sum of the depths of two facing cars, ie: 3.2 m.
As a 21 person car will generally only be filled to an average occupancy of 80% of its rated load ie: 17 persons, and only 17 persons might be waiting, then a 3.2 m width lobby would probably be sufficient. 1.4.4 Stairs, Escalators and Lifts
In general, lifts are used for “long distance” travel over a large number of floors and stairs or escalators for travel over a small number of floors. A judgement is made by the passenger with respect to the waiting time for a lift versus the walking time (and walking effort) with respect to stairs and escalators. Low rise structures, such as shopping centres, sports complexes, conference and exhibition centres, railway stations, airports, hospitals, etc. are good examples of buildings where the provision of stairs and escalators considerably aids circulation. Peters et al. (1996) provides guidance on stair usage, which can be summarised (in round numbers) as shown in Table 1.11.
Table 1.11 Stair usage
Floors travelled Usage up Usage down
1 80% 90% 2 50% 80% 3 20% 50% 4 10% 20% 5 5% 5% 6 0% 0%
In office environments the usefulness of stairs and escalators is lessened, although they can be a advantageous where (say) a heavily populated trading floor(s) must be accessed. They are also very useful for access to car parks, relieving the lifts of the
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duty to travel below the main terminal. Escalators may be used for access to the two lobby levels where double decker lifts are installed.
Table 1.12 offers some guidance to the division of passengers between lifts and escalators in offices. The use of escalators is mainly inhibited by the length of time travelling.
Table 1.12 Lifts and escalators: division of traffic
Floors travelled Escalator Lift
1 90% 10%
2 75% 25%
3 50% 50%
4 25% 75%
5 10% 90%
The provision of well signed and positioned stairs and escalators can considerably lessen the demands made on the lifts. Designers must take these factors into account.