Post 545  by Gautam Shah


Stairs and escalators are stepped and inclined-vertical transfer systems. Both provide uninterrupted transfer, unlike the modulated transfer by elevators. Traffic on stairs and escalators is restricted by the width of passage whereas the same on elevators is limited by the module size and its speed. Use of stairs requires some orthopaedic proficiency and cautious posturing, but automated escalators allow freedom to see around during the passage. Some flight of stairs can be used for accent and descent, but escalators require different sets. Though reverse escalator for descent may not be provided, as physically it is not very strenuous to climb down.

Streets of Cusco, Peru Wikipedia image by Author Rod Waddington from Kergunyah, Australia

All movements are essentially directional. A designated unidirectional system like an escalator is more efficient than a mixed movement system like a stair. This factor, however, is relevant for stairs with low to moderate traffic. There are several other transfer systems, such garbage chutes, emergency evacuation tubes, trunks or ramps, and fire-mans’ poles, where movement is unidirectional and generally downwards. The gravity accelerates the down-movement, and inclination retards the rate of passage.

Staircase and escalators at Cabot Circus shopping centre, Bristol, England Wikipedia image by Author Arpingstone

Stairs and escalators are point to point passageways, as there is no mid-way interference, except at landings. Mid-way disturbance occurs in comparatively flatter and very wide stairs over the mountain sides. Here, for ascent or descent, people cross the steps diagonally to increase the ‘tread-depth’ of the steps. Stairs generally have a pitch higher than ramps. Stairs are safer than ramps provided the person is fully mobile and orthopaedically fit, but to ascend or descend stairs are not as easy as the ramps. A ramp can have gradually variable pitch, but a stair has to have a one continuous grade of pitch.

The Grand Staircase of the RMS Olympic Wikipedia image

The inclination of steps is defined by the proportion tread versus riser of the steps. This could vary for stairs used for different purposes, ranging from steep ladders to flatter ramps like foot-ways. The dimensions of tread and riser are proportional and can be plotted on a hyperbola. Certain formulas also provide such proportions: 2T + R = 650 to 680 mm or R x T = 43000 to 45000. For steeper pitch the additional effort required to work against the gravity reduces the efficiency.

High pitch steps of ChetSingh Ghat Benaras India Wikipedia image by Author Patrick Barry from san francisco, ca, USA

Stairs have a pitch of not less than 17.30° (5:16), and of not more than of 48.30° (9:8). Below these limits it becomes a ramp or foot-way, and above it a ladder. A ladder is not a comfortable utility. Step-ladders are lower in pitch, less than 75° and require flat treads. Risers may be open or closed, for toe accommodation and handrails may or may not be provided. In the ladders’ class of stairs, some are easier to climb than others. Ladders are used for fire escapes, boiler rooms, fly galleries, attics, decks, etc. Rung ladders are pitched more steeply, above 75°, and have extremely narrow treads or round rungs to accommodate the foot. In certain cases, the space to accommodate the knee between steps may be necessary. Rung ladders usually do not require additional handrails as the side members of the ladder can be used for holding grips. Rung ladders are often caged for safety, though such cages are more useful for ascent then for descent. It is safer to climb down facing the ladder. Swimming pools, water tanks, and sewers have rung ladders. Manhole steps are very narrow in widths, but the width is otherwise compensated by its staggered placement. The same holds true, for climbers for bunk beds, whether in railways, buses, barracks or homes.

Alternating tread stairs Pinnacles National Park, California, USA Wikipedia image by Author Wing-Chi Poon

Minimum width required for low intensity unidirectional traffic is 600 mm, however most standards specify 900 as minimum width for escape in a hazardous situation. A two-way lane stair should be at least 11200 mm. Sufficient width space for movement is required at torso level, otherwise at feet level a minimum width of 250 mm is required. Where same step is to be used for placing either one of the feet, both, the step and passage widths of minimum width of 500 mm are necessary. Stairs less than 500 mm width are generally emergency stairs rarely to be used, or service stairs to be used by experienced persons. For single lane traffic 750 mm width is an accepted standard. Most of the building bylaws allow minimum 900 mm widths for private buildings. For public buildings a stair width of 1200 mm to 1500 mm is recommended. For pedestrian over bridges and other public thoroughfares, a stair width of 2400 is recommended. On public thoroughfares where traffic is totally segregated or is only one directional, the minimum stair width could be 1800 mm.

Tsarist soldiers march down the “Odessa Steps” from the Goskino film Battleship Potemkin (1925)

Same (filmed as above) Potemkin Stairs giant stairway in Odessa, Ukraine in 1990 Wikipedia image by Author Dezidor

Many stepping arrangements are used for emergency and special purposes. Simplest is a knotted rope or a rope ladder secured to a wall or column. In many countries older buildings were required to confirm to new bylaws, open iron stairways on the building’s exterior were placed. Open iron stairs, though are rendered useless by smoke from windows, so must be placed against a blank wall. One of the best fire escape stairs is a fully enclosed stairway in the building itself or in an adjoining tower. Uncoated or unprotected steel is highly hazardous during a fire as it expands and deforms the stairway. Wood though combustible catches fire slowly, and allows more escape time compared to an unprotected steel stair.

fire exit ladders in Soho. New York City 2005 Wikipedia image by Author Jorge Royan




Post 339 – by Gautam Shah


Elevators are intermittent transfer systems that moves goods and people in a direction perpendicular to the gravity. This is unlike the inclined stairs and escalators or almost parallel to the gravity systems like corridors, passages, roads, lanes and automated walkways. Elevator systems are modulated transfer systems in contrast to the uninterrupted transfer entities, and so have limited capacity of conveyance.

1 Well with bucket Ichijodani

The efficiency of a transfer system is determined by the fact whether the system is parallel, inclined or perpendicular to the gravity. The additional effort required to work against or towards the gravity, respectively retard or add to the efficiency.

2 Coal Miners- Everyday Life in a Midlands Colliery, England, UK, 19442 Miners Caged Bucket LiftThe intensity of transfer depends on whether the system operates continuously or intermittently. Continuous systems such as the escalators, automated walkways, conveyor belts, are governed by the speed of movement, while the intermittent systems such as the elevators, buses, railways are affected by the size capacity of the module, speed and frequency of service. Both systems, however have some traffic capacity limitations.

2 Old Selfridges Lift Wikipedia Image by Tony Hisgett from Birmingham, UK3 Elevator lobbyAn elevator system is capable of elevating or raising a load to a height. Lifting devices such as rope and a smooth axle were used to draw water from wells and lift building stones. The smooth axle was replaced by a wheel or pulley. The first documented proof of a lifting device is by Roman architect Vitruvius, who reports Archimedes (Greece 236 BC) building it. Ancient and medieval elevators used drive systems based on hoists or winders. These were inefficient methods. The use of a screw drive and multiple pulley systems, were the most important steps in lifting technology.

4 Scissor Lift Wikipedia Image by SmialElevators are manual, mechanical or power driven systems. Manual elevators are now used for small weights and low elevations. Manual elevators are free-fall and pulled or assisted-rise, or controlled fall-rise types. Some are partial combinations of both types, i.e. the rise may be free due to the counter weights, but fall may be controlled (such as dumb waitors from top floor kitchen facilities), or the system may work other way round. Fall is controlled by provision of a counter dead weight or parallel module. Mechanical grips that control the accelerations of speed during fall are also used. Fall is required to be controlled to avoid damage to the bucket or car module of the elevator, its resting place, noise due to impact, vibration during uncontrolled descent, spillage of liquid and breakage to fragile items like crockery etc. Fall is also required to be controlled so that stops match the required datum. Control of the rise is not very problematic in manual elevators, because there is no self acceleration during ascent. Rise of a weight (dead or a purposive load) to be elevated, is accurately controlled by the amount of energy expended. However some control mechanism to maintain the rise once gained, is required. Such dumb waitors are used between kitchen and serving areas, godowns and delivery areas, documents and spare parts transfer in commerce and industries.

4 Dumbwaiter geograph-4379493-by-Bill-Nicholls

Bucket-lifts were common for water wheels in India, Persia and many other countries. Bucket-lifts were also used to lift ore and coal from deep mines, and transfer miners. An air lift system works on a suction mechanism to transfer materials.

The classifications here are oversimplified discussions for the non technical people.

Mechanical Elevators use some form of chain pulley system or other devices to reduce the energy required. Such elevators are capable of lifting larger loads than dumb waitors. In some cases the elevators are designed as quasi mechanical systems, where rise is through a mechanical or power driven system, but the fall is natural but controlled. Such systems are used where, loads heavier than the manual capacity are to be lifted, power supply is erratic or not available, lifting requirements are occasional.

6 Mechanical Lift geograph-734490-by-Stephen-Sweeney

Power driven elevators are generally motorized, where an electric motor creates a hydraulic pressure or winds a traction rope to elevate a weight. These elevators work on DC current to regulate the start, speed and stop.

2 miners mechanical hoist

Hydraulic Elevators are not extensively used now, however, are ideal for low rise building where design limitations preclude overhead supports and machine rooms or load-bearing walls around lift well. The machine room can be located nearly anywhere, and let one maintain a flat roof line and save money on construction. Geared traction elevators are ideal for low-to medium-rise buildings, where high speeds are not essential, though speeds up to 400 ft/min. can be planned. Gear-less traction elevators are recommended for high-rise applications requiring the ultimate in service-speeds of 500ft/min and up.

Eiffel Tower Lift Cars

Passenger elevators are wide and shallow in depth, with centre-opening double doors or single side doors. Service-elevators, like for hospitals, are narrow and deep. Combination passenger and service elevators should be almost square. Freight elevators’ size and shape are determined by the dimensions of goods to be carried and by the loading / unloading methods used, but nominally allow carriage of 1200×2400 sheet materials.


While providing elevator system in a building, two basic norms are considered. The frequency and quantity of service required, and the quality of services desired. The quantity of services is determined by the passenger handling capacity during peak periods, while the quality of service is measured in terms of time required (waiting time) to avail a lift. The quality of elevator service is determined by the building planning, intensity of peak hour requirements, extent and duration of traffic, frequency and urgency of service required, type and control mechanisms, type of landing doors, etc.

Pan Pacific Singapore Open or Bubble elevators Wikipedia Image by SanchomOperation of lifts: Modern lifts have an electronically intelligent control system that actuates starting, stopping, door opening and closing, direction of motion, acceleration, speed and retardation, emergency smooth fall of the lift car. A variety of motors are used to power the lifts. The simplest is single speed resistant AC motors, the reduction gear is attached to the pulley, braking is semi mechanical, or through an additional motor, generally a DC motor. In a little more complex setup reduction gears are attached to the motor and a secondary winding is provided to stop the motor. More complex and accurate system consists of a DC motor. With DC motor input voltage can vary the output speeds, step-less gear system is often integral part of the motor. Such systems provide very high speeds, accurate stopping, less jerks and smooth operation.

11 Platform_window_cleaner

12 Bus Elevator for wheel chairs Image credits Aktron Wikimedia Commons.Elevators are prerequisite requirements for buildings taller than 3 floors. Elevators are often a legal requirement in public buildings because of wheelchair access laws.



Post 153by Gautam Shah



A building has many types of systems such as openings systems, services systems, structural and non-structural systems, etc. Transfer Systems denote a very large group of subsystems used for transferring goods and people in various directions, levels and in different modes. These are intentionally facilitated by architectural design or naturally occur irrespective of the adequate provisions in the building fabric.


Two way system defined by L-R preference for passage But this could be culture and country specific behaviour > Durga Puja festival in Kolkata Wikipedia Image by Biswarup Ganguly

Transfer Systems mark the routes or spaces where concentrated or repeated movement of people and goods occur. Stairs, ramps, elevators, escalators, corridors, passages, bridges, etc. are elements or systems that can be identified as transfer systems. The transfer system denotes an exclusive one or the most efficient node available, leading to concentration of traffic.


Mixed traffic crates chaos

The efficiency of a transfer system is determined by the fact whether the system is parallel, inclined or perpendicular to the gravity. The additional effort required to work against or towards the gravity, respectively retard or add to the efficiency.

Le Corbusier Ramps -inclined transfer systems

Transfer system denotes movements which start and terminate somewhere. Simple transfer systems have one to one point articulation. Branched transfer systems have one to many points configuration. It may start or end at multiple points. The third option where many to many points transfer start or end, it results in chaos, and there is no system identity.

Transfer systems are parallel -horizontal to the earth, perpendicular -vertical or inclined towards -downwards or against -upwards the gravity. Passages, Roads, Corridors, Automated walkways, are almost parallel to the gravity. Stairs and Escalators are inclined towards or against to the gravity. Elevators are perpendicular to the gravity. All these are designed to allow greater concentration of traffic, compared to many other parallel to gravity areas like Chowks, compounds, plazas, etc.

Walkway or Travelators at Indira Gandhi International Airport, Delhi Wikipedia Image by Vineetmbbsat

All movements are essentially bidirectional, though through design the movements may be bifurcated in time and space. An unidirectional or segregated system is more efficient than any bidirectional or multi-directional (mixed) movement systems. In a built environment too many multi-directional movements confuse clear identity of a transfer system. Within such chaos ultimately all movements cease.

Transfer systems are open-ended or looped. Open-ended systems have finite start and termination points. Start-point is one where the first transferee element gets on the transfer system. The end point is one where the last of the transferee element gets off. It is also a point where another system such as the reverse, or parallel movement system begins. Looped systems are continuous systems and have no start-points or terminal points. Looped systems have a circular formation, or part of the segment is connected by straight (point to point) transfer system.

Circular spiral -but nor a looped transfer system

The intensity of transfer depends on whether the system operates continuously or intermittently. Continuous systems such as the escalators, automated walkways, are governed by the speed of movement, while the intermittent systems such as the elevators, buses, railways are affected by the frequency of movement’s module. Both systems however have a traffic capacity limitation.


In a transfer system, people move depending on two counts, anthropometric design of the system, and orthopaedic functionality. On other hand vehicles or goods modules are carried by use of external energy through mechanical devices. Variable capacities of the transferee also affect the speed of transfer, and as a result the intensity of traffic.

Escalator as continuous inclined transfer system

Transfer systems are disturbed when elements moving at different pace cause an unwanted change in the speed or direction of the general moving mass. Transfer systems become invalid when all goods and people reach their destinations, or when there is nothing left to transfer.


Transfer systems necessarily have start-end nodes, but most transfer systems have multiple intermediate exit and entry nodes or points of transfer on the route. Some points of transfer are very clearly defined, like a door in a corridor, railway station, but many others nodes are not clearly delineated such as path or footpath without a barricade.

Multiple transfer systems -too close

Transfer systems that are exclusively directional, with high speed or of mixed traffic, require highly defined points of transfer. At every point of transfer goods and people have to alter the direction and change the speed of movement to embark or disembark the transfer system. Such variations in movements at every entry or exit node reduce the overall efficiency of a transfer system, unless points of transfer provide necessary definitions. Points of transfer provide visual and other information about the available options. A subsidiary system often allows a slow-moving transferee to adjust the speed and direction before moving over to the fast-slow moving system.


Straight transfer systems have greater efficiency, than any sharp twisting turning system. Transfer systems directed towards gravity or any superior environment such as towards promising – enticing situations tend to have greater efficiency. Point to point systems are superior to continuous systems with many points of transfer on the route. Transfer system with designed points of transfer operate better.

Railway -well defined transfer system