THE IN-LINE ACCELERATING MOVING WALKWAY
by John Loder, Loder Transport Systems Pty. Ltd.

Summary

This article describes the world's first in-line accelerating moving walkway to operate in a public facility, tracing the history of attempts to develop accelerating systems, outlining the development of the Loderway Accelerating Walkway and describing the features of the Loderway systems. The Loderway is a discontinuous system, using a sequence of individually driven, thin, flat slider belts. Acceleration and deceleration is achieved by small changes in the speed of sequential short belts at the start and finish of any installation. The long central belt runs at the highest speed of the system. Individual central belts may be up to 200 metres long, but the overall system length between the acceleration and deceleration sections is unlimited. This is possible because passengers are automatically transferred from one main belt to the next over the 2.0-mm gap without their being aware of it.

History

Brian Richard's excellent book, Moving in Cities, describes, amongst other early systems, an installation in the Paris, France exhibition of 1900. This 3.4-km system used two parallel tracks made of interlocking platforms running at 1.0 m/sec and 2.0 m/sec with nine stations from which passengers stepped onto the inner, and slower, of the two concentric tracks. It ran for eight months and carried 6.5 million passengers with only 40 minor accidents.

The following six decades did not see much progress in the development of faster-than-walking speed systems. Then, in the 1970s and early 1980s, many millions of dollars were spent by such people as the Paris Metro, Dunlop Engineering, Boeing Aircraft and others on the development of in-line accelerating walkway systems. All these groups were responding to a large market for systems travelling at higher speeds than those currently deployed. Although a number of these systems were developed to pre-production prototypes as long as 170 metres, none were ever commercialised.

The problem with all the systems lay in their mechanical complexity, a complexity that was constant for every metre of each system. This complexity resulted in a cost per metre which was 300% to 500% higher than existing single-speed systems, presented a difficult noise problem with some systems, had numerous possible entrapment points and also raised doubts about long-term mechanical reliability.

It is also fair to say that the systems of the 1970s aimed, rather optimistically, for speed ratios of 3 to 5, which in itself presented noise and bunching problems that are not a problem at lower ratios.

Background to the In-Line Accelerating Moving Walkway

The in-line accelerating moving walkway systems arose from an attempt the author made when a principal of an urban planning consultancy (specialising in urban transport) to devise an accelerating system based on a cheaper and simpler approach than used previously. This followed an inability to find a movement system to connect a car park and a marina, which were 500 metres apart, in a reasonable time without undue physical intrusion.

The key to an economic system soon became apparent; the secret of success had to lie in devising a discontinuous system, where the accelerating and decelerating segments were physically separated from the long high-speed section. Only in this way could the costs of the complicated speed change areas be prevented from raising the overall cost unduly. All the previous systems which had been seriously developed carried the same mechanical complexity for the full length of the system.

The systems now developed are the result of a process of build, use, re-build and re-use. At the same time, there has been a constant program of development with belting manufacturers to produce belts specifically designed for high flexibility, long life and high passenger appeal.

The in-line accelerating moving walkway system is not merely an idea or a factory demonstration model. A middle-speed accelerating system is running at Qantas Airways' domestic terminal at Melbourne Airport. Previous demonstrations of the high-speed model have been performed at Brisbane airport (see photo above), and another middle-speed demonstration ran for two years at the central railway station in Melbourne, Australia without incident and with great passenger appeal. It was only removed to allow a renovation of the area of the station in which it had been installed.

This is not a system which may be safe; it is a system which has demonstrated its safety in the real world and been subjected to rough-house treatment by groups of youths riding, jumping, roller blading and making rushing leaps in the wrong direction onto the speed-change belts. It did not falter. The system design has now been refined further, to reduce noise dramatically and improve appearance, and firm prices can now be quoted and commercial orders taken.

The in-line accelerating moving walkway system comprises a sequence of discrete, endless slider belts with a flat (nonribbed) surface. Each belt is separated from the next by a gap of one to two millimetres, with sequential belts operating at slightly different speeds to effect acceleration and deceleration. The short acceleration and deceleration belts turn around 26-mm-diameter rollers, and the long central belt, operating at the highest speed of the system, turns around 45-mm-diameter rollers.

The transfer from one belt to the next requires no action or even attention on the part of the passenger. The diameter of the rollers and the speed of the belts are interrelated, so even a pointed object is safely and comfortably transferred across the gap between belts. To reduce belt wear on the thinner belts used on the speed change modules, there is a drop of five millimetres from one belt to the next, so even stiletto heels (see Figure 1) land on top of the following belt and not at an angle over the roller. Note that in the railway station installation, after two years of rough use, even the short belts had suffered no appreciable wear, and no deterioration of the splices were evident.

Depending upon system type, the one to six metres of acceleration or deceleration at each end of the system are more expensive than an equivalent length of a single-speed system. However, the balance of the length is a simple slider belt operating over a 5.0-mm steel slider plate. So, depending upon length, this reduces the overall cost to a level competitive with current single-speed systems.

The in-line accelerating moving walkway design addresses three problems of existing systems, namely:

u they travel only at the entry speed, which is limited to the speed at which passengers can safely step onto and off of the system, usually about 0.6 m/sec or half walking speed;

* they are of rigid metal pallet design which provides a rigid grooved surface, which some people find slippery, particularly on inclines, or edge-supported slightly undulating rubber-ribbed belting, with the attendant problem of rib wear; and

* they all terminate at combs whose fingers can engage torn shoe fabric, shoelaces and stiletto heels, which have gone between the ribs on the belt or pallet surface, with resultant accident and maintenance problems (broken combs, a not infrequent occurrence, can accentuate the problem severely).

The in-line accelerating moving walkway range of systems provides two to three times the speed with the enhanced safety features discussed later in this article. The simplicity of the design results in high reliability and provides significant installation advantages over other systems. The systems illustrated were installed directly onto existing floors without any structural strengthening or modification required.

Figure 2 shows the layout of a typical high-speed system, with six short and one long speed-change belt and a single handrail change at each end.

A passenger stepping onto the first belt with one foot will have this foot transferred to the second belt by the time the second foot is placed alongside it. In less than a second, both feet are passed to the longer fourth belt, which is running at the speed of the first handrail, and the first acceleration phase is completed. At the end of the ride on the fourth belt, a handrail change is made before the second acceleration phase is commenced. This second phase of about a second occurs over the next three short belts before reaching the main highest speed belt, which is running at the same speed as the second long handrail. With such a sequence, speed may be increased from the entry 0.6 m/sec to the main belt speed of 1.8 m/sec. The sequence is repeated in reverse at the exit end, with a final belt speed of 0.75 m/sec to limit the bunching effect.

The middle-speed in-line accelerating moving walkway provides a speed increase from 0.6 m/sec to 1.2 m/sec. The system is very simple, using only three half-metre belts at each end of the main belt, as well as only one handrail on each side. The acceleration is over about half a second after the stepping on has been completed, and no handrail change is necessary. This type of system is good for lengths up to 120 metres, depending on circumstances and the total length of any run of installations. Above this length, the higher speed system may be warranted.

The systems have a depth below belt level of only 260 millimetres. This depth contains all the accelerating and decelerating system, the handrail drive and the main belt drive system. The main motor can be located between directions of travel above the floor or, if there is room, below the system.

The increase in speed from one belt to the next is small, averaging about 0.2 m/sec, and the jerk on transfer is small. These small jerks are accommodated well by the human muscular/skeletal system ­ a system designed to keep the body's centre of gravity moving smoothly forward while the feet are doing a lot of accelerating and decelerating.

Safety

The three main areas of concern with regard to the safety of an accelerating system are upsetting, entrapment, bunching and system malfunction. Each is discussed below.

Upsetting

The maximum upsetting effect experienced occurs when passengers step onto the first belt and, if they step on tentatively, can go from 0 to 0.6 m/sec. Some people fall getting onto single-speed systems at this point, and the in-line accelerating moving walkway is the same in this area. From this point onward, accelerations are lower and are much less than those experienced by standing passengers in buses, trams and trains. An erect human being is in a constant state of unstable equilibrium. People able to stand unaided have the ability to move their feet in order to retain their balance.

Passengers use the in-line accelerating moving walkway with respect for their abilities. The young often walk straight down the system without using the handrails; the elderly hold the handrails and step on carefully. The entrance signing is eye-catching and advises that this is a high-speed system and the handrails must be used. People with stability problems hold the handrails under these conditions and make safe trips. The first trip on the first accelerating system is, of necessity, a journey into the unknown, but it is safe. Subsequent trips are without surprises. We have not found upsetting to be a problem, and neither did the Australian Walkway Code Committee.

Entrapment

Nothing can be caught between the rollers, even in the deceleration area where the in-going belt travels faster than the one coming out. This is because solid objects "fly" across the gap, and even if expanding flexible material - such as clothing - reaches the gap, it is, if attached to a passenger, pulled by the forward movement of the passenger onto the outgoing belt, thereby preventing ingestion. Even if pressed against the gap, it will not go in. Fingers can be pushed against the gap without harm, although in normal use they too would "fly" over the gap.

At the end of the system, the in-line accelerating moving walkway does not need to use the ribs and combs that cause so much trouble on conventional systems. Solid objects pass over the 5.0-mm gap between the belt and the top plate and land on the fixed top plate of the patented double-plate configuration. If flexible material is somehow pushed through this gap and then through the 1.5-mm gap between the bottom plate and the belt, the pivoted bottom plate is forced away from the belt. This releases the material and at the same time activates a switch which brings the system to a controlled stop. In addition, a separately patented light beam looks for sequential gaps in its field of view. A trapped passenger or a stationary piece of luggage blocking the exit will stop the system. Because ribs and combs are mandated throughout the world, many people expect considerable opposition from safety authorities to this new system using flat belts. Experience has shown that, once viewed in action, the in-line accelerating moving walkway system is so demonstrably safer than conventional systems that resistance to its use has not occurred.

The sequential handrails come within 100 millimetres of each other to ensure no possibility of entrapment. This gap represents a transit time of about 0.08 sec and is not significant for the passenger. Placing anything between handrails to provide a smooth top surface resulted in pinch points, and leaving a gap eliminates any entrapment possibility.

Bunching

In-line accelerating systems have a potential bunching problem when passengers spread out during acceleration walk up to other passengers on the high-speed section. When the deceleration takes place and the spacing of standing passengers decreases, there is the possibility of them running into each other and pushing each other over.

Trials at Johns Hopkins University in the 1970s indicated that, at speed ratios of 3:1, there would not be any safety problem, but field experience was needed with passengers who had no prior knowledge of the system to validate this expectation. We can now say with confidence that, while steps may well be necessary to ensure adequate passenger spacing approaching the deceleration area with speed ratios of 5:1 or so, bunching is definitely not a problem with the main belt running two-and-a-half times that of the last belt, as it does in the in-line accelerating moving walkway high-speed systems.

The personal comfort zone of passengers ­ including people from cultures with a smaller comfort zone than Europeans usually possess ­ ensures that there is sufficient "slack" available for people to move closer together during deceleration without any chance of someone being pushed over or even feeling discomforted. In the first airport trial, Japanese tourist groups, once acceleration spread them out, moved closer together on the central belt to discuss the new system. Even with these comparatively crowded groups approaching the deceleration area, no one commented on a bunching problem, nor were there any signs of a problem.

System Malfunction

Discontinuous accelerating systems have the potential for one segment to stop or operate at the wrong speed, with consequent safety problems as passengers are transferred to the problem area. The in-line accelerating moving walkway responds to this potential problem by constantly monitoring the speed of all belts and handrails; if they run more than a nominated percentage fast or slow, the system comes to a controlled stop. All belts are also monitored for position, and if too far out of position, the system is shut down. In all, 32 functions are monitored by the central PLC on the high-speed systems.

Detailed System Characteristics

The Belts

The belting used for the system has a textured polyurethane topping. The polyurethane on the main belt is 1.5-mm thick and enormously resistant to wear. Most industrial belting has a topping ranging from 0.2-0.7 millimetres for the toughest applications, such as carrying metal castings or bricks. The life of the short belts on the modules at the ends will be over two years, and the life of the main belt is expected to be more than seven years, the actual life depending on the level of use. Baggage is handled in airports by slider belts, which have fairly rough use from the things that are dropped onto them, yet these belts commonly last more than 10 years. This is for belting developed more than 10 years ago which was of much less sophisticated design than belting currently available. The fabric bottom of the belts has a friction factor of only 0.15 with the steel slider bed.

Maximum System Length

There is no limit to the length of any of the accelerating systems. When the strength of one belt has been fully utilised, another belt and drive is commenced, with the passengers being transferred automatically from one to the next, as in the speed-change areas but without a change in speed at this point. Single high-speed belts may run up to 200 metres.

Grades

Full speed should be allowed up to 3° of slope, reducing uniformly to 0.9 m/sec at 8° and then to 0.75 at 12°. The Australian Code allows these figures.

Vertical Curves

Summit curves present no problem to the system, as it is just a matter of shaping the slider bed. Sag curves cannot be accommodated directly, due to the tendency of the belt to pull into a chord across the sag. A sag curve can be implemented by using short modules about 500 millimetres long acting as a series of chords. Each "kink" can be up to 4° without problems for the passengers.

Fire Rating

The belts are noncombustible and can be made to any fire rating required. All bearings are fully sealed, and the drive system requires no lubrication. The whole system is, therefore, very fire resistant.

Power

While quite large motors are required to cope with the absolute maximum load of the system, the actual power consumption is small. Most systems run much of the time with low load, and an unloaded slider system uses little power. To give an idea of the power consumed, 1,000 passengers transported 100 metres at 1.7 m/sec uses about 3.0 kW hours of power ­ a small amount.

Maintenance

The systems are designed for long life and low maintenance. Periodic inspection will find bearing distress before failure, and replacement of drive belts and module belts can be scheduled for after-hours replacement. The system is inherently simple, with fewer moving parts than pallet systems, and experience has shown that maintenance costs should be the same or less than for single-speed systems.

Capacity

The capacity of the accelerating systems is the same as for single-speed systems, both being controlled by the entry rate. Many manufacturers assume that two people will enter two abreast and 400 millimetres apart, which at an entry speed of 0.7 m/sec gives a capacity of 12,600 passengers per hour. In practice, such figures are not achieved on walkways, as a crowd does not wait to get on for a whole hour, and many gaps occur due to the different behaviour of individuals. A figure nearer 5,000 per hour would appear more realistic. Higher capacities would require duplicate systems operating side by side.

Handrail Drives

The handrails are driven by a multiple pinch-drive assembly for the main handrail, and a single pinch-drive for any short handrail on the system.

Costs

Because the ends are relatively expensive and the middle sections are relatively cheap, the overall cost of the systems is related to length. In general terms, in-line accelerating moving walkway systems will range in per metre price up to a ceiling of 20% more than single-speed systems for short lengths and will generally be less expensive for longer lengths.

Code Compliance

Because the accelerating systems have so many features in common with single-speed systems, they must deal with the codes of practice covering those systems. This means working toward changing and expanding the codes to incorporate accelerating systems and to allow the double end plate design as an alternative to the use of ribs and combs. Fortunately, all the major national codes allow for exemptions to the code for the initial installation of new systems. This was the route taken in Australia, where a code now allows all the features of our accelerating systems, and this will be the route followed elsewhere.

Single-Speed Systems

Single-speed Loderway systems using the same slider belt technique and the patented double end plate system have advantages over current single-speed systems. They are more economic, easily retro-fittable, safer at the end and provide a much more stable surface to stand on ­ particularly on inclines. A single-speed system on a 15° slope has been operating in Melbourne for 5-1/2 years.

Patents

The Loderway accelerating moving walkway systems are covered by patents currently granted in the major manufacturing countries of Europe, U.S., Japan, Australia, Singapore, Hong Kong and Taiwan. Other patents are pending in South Korea, Canada and Brazil.

The Future of the Technology

Loder Transport Systems in Austraulia is now offering for sale all it patents and design technology, with on-going support; phone: (61) 3-5473-4599 or fax: (61) 3-5473-4223. c