Elevated Railways: The What, The How And The Why

This blog has been dormant for quite a while (for which I apologise) but I seem to have become involved in quite an array of activities, all of which have made demands on my time. However, some of them were relevant to the topics discussed here. On one occasion, I visited a very interesting (and for me, quite nostalgic) web site called RailPage Australia (http://www.railpage.com.au/) where I was able to discuss some of the transport infrastructure ideas I described earlier in this blog (see  Infrastructure 2. Modes Of Access) with some very knowledgeable people in the railways field. I described the structural model expecting some discussion on the technical aspects of construction, but the most useful insights came from some of the respondents who basically asked two questions. The first was “How do you propose to build such a structure, particularly in very remote areas?”. The second was “Why do you want to construct railways in this form, rather than the traditional one?”.

These are valid and important questions and this post will hopefully provide acceptable answers to them and also to other implied questions.


I have already stated that there is a a set of longitudinal steel beams supported on A-frames, which are  transverse beams supported on legs that splay outwards to provide lateral stability. However, we must look at these components in some detail, because their design is governed as much by the construction methodology as by the required load-bearing capacity.

A driver for the design of the structure is that most of the erection will be done in remote areas, where there may not even be road surfaces sufficiently strong enough or wide enough to transport the materials. This implies that the railway itself will be the supply line carrying components for prefabricated construction at the railhead. The prefabrication elements will need to have appropriate dimensions and weight to be carried on specially designed railway wagons. The A-frame legs and the longitudinal beams will be of lattice construction to provide the maximum strength from a minimal amount of steel.

Between the longitudinal beams will be steel troughs (one for each direction) and, if desired, space could be left between them for a dedicated VFT line, such as a Maglev. Rails will be attached to the floor of the trough for regular trains. MonoCabs and similar vehicles equipped with rubber-tyred wheels will straddle the rails and ride on the floor of the trough. They will be held in transverse location by outriggers with wheels at their outer end, which will roll along the vertical walls of the trough.

This geometry raises some issues for the MonoCab style of vehicle whenever crossovers and junctions are encountered. However, there are a number of solutions that could be adopted.

  • The outriggers could be extensible in a concertina fashion and be attached at the corners of the vehicle where they would be able to swing forwards and back. This would allow the forward-reaching outriggers to land on the branching trough before the rearward ones became detached from the main trough.
  • Another possibility would be to place the wheels above the outrigger and, where necessary have an L-shaped plate attached to the trough wall and hanging over the wheel. The outrigger could then become bidirectional, pushing or pulling against the trough wall as required.
  • Finally, the stabilising wheels could be located under the carriage, riding in a channel. When it becomes necessary for the vehicle to cross the track, one of the two sets of stabilising wheels would be raised up to cross the track, followed by the second set after the first had descended into the channel again on the other side of the track. In the region of the junction, the surface upon which the vehicle rides would be raised up to the same level as the track, which at that point would resemble a tram track.

Platforms at stations would be located along the outer edges of the track, with ramps or stairs leading down to the station building, which would be located below the tracks. City terminals often have very high ceilings or glazed roofs, so it should be possible for elevated railways to reach and use such stations with very little impact on pre-existing infrastructure and services.

Opportunities exist for the provision of ducts housing water pipes, power cables, telephone cables, optical fibre cables and other services, which would improve the economics of constructing the railways significantly. It might even be possible to use the trough as a water catchment for agricultural use or fire fighting.


The first railways were built in England, from one pre-existing town to another, in order to transport passengers and goods. In other, less well-developed places, the general model was to set out from a starting point and head towards a target finishing point. Thus, American railways were, in the beginning at least, intended to connect the Pacific and Atlantic coasts. In East Africa, the first railway was built to connect the East Coast to Lake Victoria. In Europe, many railways were originally designed to connect capital cities directly to border points, where they could, in turn, connect up to railways in an adjoining country. A most interesting book called “Blood, Iron and Gold: How Railways Transformed The World” by Christian Wolmar describes the policies and drivers which led to the construction of these seminal railway systems. Where there were no existing local roads to service the construction process, very often, a road alongside the track was built for the purpose and then was either connected into the existing or future road system, or was simply retained for maintenance purposes.

In the USA, Australia and East Africa (I worked on railway design and construction in the latter two), the land consisted almost entirely of broad open spaces. Such settlements as there were existed to extract or grow marketable food and materials. The usual modes of transport were horses and carts or camel trains, travelling cross-country directly from point to point. There were few, if any, roads as we would understand them. When the decisions were made to build the railways, heavy reliance was placed upon the information provided by explorers, hunters and the like. Ownership of the land by local tribes was, in general, ignored. Once the overarching route had been sketched in, construction would commence from the starting point. Detailed surveying would be carried out ahead of the advancing railhead. In general, because the countryside was considered to be undeveloped, large-scale earthworks and structures were rejected in favour of diversions. Looking at some of these older railway tracks on (say) Google Earth, it is amazing to see great looping curves alternating with straight sections stretching for many kilometres. Where the impediments were really colossal (the Rift Valley in Kenya, for instance), structures such as loops (where  the track would curve around in a circle, gaining height, eventually crossing itself with a bridge) or switchbacks (where the track would zig-zag up an escarpment, with trains reversing at each extremity) would be employed to gain height.

Compare this process with the one mostly employed in highly developed areas., where the space allocated to a railway line is restricted by buildings, dams, parks, treatment works and so forth. In order to keep gradients within operational limits, substantial earthworks and even tunnels may be required. This approach is practical, because in the main, sites are located within easy reach of power, water, roads and other infrastructure to facilitate the construction work. There are also possible efficiencies in that construction can take place at a number of points along the line simultaneously

The general thesis behind this blog is that food production and population absorption may, in the future, require the construction of settlements in remote areas to take advantage of relatively limited and heavily localised resources. These settlements will in effect be oases in a relatively barren landscape, with the railway being, in the initial stages, at least, the prime and possibly only form of transport connection to the outside world. One can argue that the required developmental model is similar to that used in the three continents mentioned earlier. However, there is one important difference. In those places, rural and commercial development followed in fairly short order, so that after the first extensions into the hinterland, a wide range of resources such as construction equipment, housing, support services, etc. became available. In the current Australian context, the railway lines will be connecting a lot of dots on the map and construction will be almost totally reliant on personnel, materials and equipment carried to the railhead on the railway itself.

Within the construction zone, both the up and down lines will need  to be used bidirectionally. The former will carry equipment, such as cranes, tractors, concrete pumps and like. The latter will carry construction materials, personnel and supplies. Trains will need to have a control cabin at each end and will, in general, travel backwards and forwards on the same line during the construction phase (though it may be feasible to construct two-way crossovers at a few convenient points).

For each span, construction will follow the same sequence of events:

  • In the most general case, foundations will consist of reinforced or prestressed concrete slabs spanning between the grounding points of the A-frame legs. In soft ground, the slabs may need to be supported on Frankipiles. Where the railway is crossing a flood-plain, some of these Frankipiles on the downstream side may need to be angled away from the vertical to provide lateral support against flooding.
  • It may be necessary to construct intermediate foundations to support temporary framing which in turn will support deck elements as they are advanced towards the next permanent A-frame. Alternatively, it may be possible to suspend the beams from a horizontal crane with substantial kentledge at the rear.
  • Fabrication of the deck from the shipped-in components will be carried out on a deck sitting on wagons side-by-side on each line. As each section (approximating in length to the distance between two adjacent temporary or permanent A-frames) is completed, it is rolled forward until it rests on the leading A-frame. The next section of deck will be constructed by extending the previously completed section backwards and then rolling the entire structure forwards. Once a span between two permanent A-frames is completed, the assembly deck can be rolled forward.
  • One of the greatest problems affecting rail construction in Australia is the very large variation in temperature. In Central Australia, one can encounter a temperature range in the order of 15 to 50 degrees Celsius. When railway lines are subjected to variations of this order they expand and contract linearly. Because they are pinned down to the ground, these movements cannot take place and this causes the stresses in the rails to rise. In effect they behave like columns. If columns are too thin, they tend to buckle sideways under the load. Except in cases where the railway line components have all been expressly designed to handle extreme temperature ranges (as in some of the ore-carrying lines in Northern Australia, for instance, it is quite common (in older lines, at least) to see tracks which have buckled sideways or lifted clean off the ground because the sleepers were not adequately anchored into the ground or were not strong enough and splintered under the load. In general terms, the lattice frame structure and the trough deck will provide a sufficient lateral dimension to ensure that buckling does not take place, but the corollary is that the connections between components must be strong enough to ensure that no separation takes place and the spatial geometry remains intact.

I must emphasise that the structures  I have described here are speculative and not prescriptive. Other designs appropriate to the terrain and the construction process are entirely possible. My main intention is to demonstrate that there is at least one modus operandi available and the concept does not deserve to be rejected for lack of viability.


3.1.          Reduced Impact On Ground Conditions.

A very important reason is that the construction work is as independent of the local ground conditions as it is possible to be. The entire deck is assembled from a kit of parts which, for the standard model, does not vary at all. The only items which are affected by the on-site ground conditions are the lengths of the A-frame legs and the nature and design of the foundations.  Of course, there will always be variations dependent on those conditions. Here are some possiblities:

  • It may be necessary to drive the line through a mountain range via a cutting. The amount of excavation required for the elevated railway is only a fraction of that required for the same location at ground level. To prove this point, imagine that the cutting cross-section is an inverted triangle. Assume also that the height of the elevated track is midway between ground level and the highest point of the range. If one draws a line through the triangle at a point half-way between the top and the bottom, one can see that the amount of excavation required for the smaller triangle (the cross-section required for the elevated railway) is only one-quarter that of the larger triangle.
  • There are many salt flats and shallow lakes in Central Australia. Where it is necessary for a train to cross such features, the need for drainage to expose the underlying ground level can totally compromise the value of the feature as an aid to biodiversity. By contrast, the above-ground structure can simply be erected upon piled foundations with very little effect on the local wildlife.
  • Similar considerations apply to routes which cross river valleys and flood-plains. An elevated railway can keep functioning (provided the water level does not spill over the track, of course!) in situations where conventional railways are not able to operate and, worse still, the track is at risk of significant damage, necessitating expensive repairs after the floods have receded.

3.2.          Interaction With The Economy.

One can argue that over a single kilometre of flat ground, conventional track is cheaper than the elevated version. However, this simplistic view fails to take into account a number of ancillary benefits which elevated railways confer on the economy.

I worked as a civil/structural engineer on a variety of projects until the early 1980s, after which I moved over into the IT world. In my earlier career, the standard method of paying the design consultants (who would also supervise the construction) was through a fee which was a percentage of the completed project (usually 6%). This was enough, not only to complete the finalised design, but also to spend time examining alternatives and looking in detail at any advanced technological features about which there was not much field experience reported. These opportunities disappeared with the outsourcing of projects, where competitive tendering forced design consortiums to produce, at first attempt, a design which would cost the least to build or if there is any technical uncertainty, could attract contract arangements which would pay out cost over-runs. In other words, there was no margin for error. This model was further complicated by the introduction of public/private partnerships where the complex financial arrangements allowed organisations such as the notorious Babcock and Brown to expand their income hugely by creating hierarchies of companies, each of which paid management fees to the next company up the chain. The end result is that, in the main, we are paying far too much for our infrastructure, for the purely political reason that governments prefer to keep such projects off their books.

The beauty of the elevated railway design discussed here is that most of its features are constant from project to project. Any difficulties encountered on a project or any new ideas tried out become part of the pool of knowledge and will be reflected in the more competitive prices of future contracts. Contractors will be awarded projects directly from the government on the basis of their efficiency, experience and ingenuity with none of the risks exposed in Victoria’s hugely expensive desalination plant (to name but one PPP disaster). Because the concept is so straightforward, and the function of the railway is to assist in the development of new outback areas (initiatives which will hopefully have been rigorously assessed), projects of this kind will be attractive to investors and governments should be able to issue bonds to cover the cost at a very attractive rate.

One of the most profound impacts on the economy is that the railway will consume a very large amount of steel. Currently, the manufacturing side of the steel industry is not in very good shape, partly because of the high value of the Australian dollar and partly because of government-subsidised steel activities in other countries, particularly China. These circumstances make it possible for raw iron ore to be shipped to China, turned into iron, used for the manufacture of structural components or household equipment and shipped back to Australia at prices that our steel manufacturing industry cannot match. If it is specified that only Australian steel can be used in railway construction, this should provide a substantial boost to the local industry. Furthermore, as the components of the above-ground structure are heavily standardised, contracts for manufacture and storage can be awarded to many different companies around Australia, ensuring that any benefits are uniformly distributed. Finally, as steel is a recyclable material, an upgrade or a dismantiling of a line offers materials that can be re-used on other projects or, at a minimum, melted down and cast into other usable items.

There are many places in the world which have arid terrains similar to those in Australia. Interesting possibilities exist, therefore, for the sale of the technology and materials or for their inclusion in aid programmes.

3.3.          Interaction With Other Commercial and Personal Activities.

When an on-ground railway line passes through agricultural land, significant access problems are created and these are exacerbated as the average speed of services increases. Crossing points such as bridges and level crossings must be created. The former are expensive to build and are therefore likely to be inconvenient distances apart, requiring significant detours (to access remote parts of a farm, for instance). The latter are simply too dangerous to be allowed on a high-speed line, unless electronically controlled barriers are installed. These too are very expensive in remote areas, where electricity supplies may be sparse. Overhead railways, on the other hand, preserve the current farm operating procedures to the maximum extent possible. There are some bonuses, too.  Firstly, there is little, if any, loss of land to a railway reservation. Secondly, the A-frame columns could support cladding, creating glass-houses, shelters for poultry (where a battery system can be modified to allow periodic access to the adjacent pasture for the poultry) or simply storage for equipment, materials and crops. These possibilities can significantly enhance the farming activities.

Noting that the railway services will, in the main, be electronically controlled from terminal points or stations, it is feasible to set up daily time zones where fast passenger and goods services are despatched after which the lines are available for privately-hired car-carrying Monocabs and other passenger and commercial vehicles to follow them. They will slowly fall behind the fast trains and the trains despatched in the next time-zone will slowly catch them up, but the remote controls will ensure that collisions will not occur in the event of any unscheduled stoppage. Hence, there are substantial opportunities for privately- and publicly-owned services to share the lines.

3.4.          And In Conclusion…

This blog is intended to provide possible models for the management and development of Australia and its resources at some future time when population and food production pressures have reached very high levels and we need to maximise the return on every agricultural and manufacturing capability we have. However, if we wait until this necessity really bears down on us heavily, it may be too late to derive the maximum benefit from them, because time will still need to be spent on identifying the optimal models, setting up manufacturing lines and so forth. It would seem prudent, therefore, to prepare some alternative designs and do some testing before then, so that when the time comes, we can immediately undertake every task that the situation calls for.

So far as the overhead railways are concerned, we may possibly have some immediate opportunities for designing, testing and constructing some trial sections of overhead railroad. A few days ago, there were several articles in the local press, discussing the proposed introduction of B-triple vehicles on interstate highways. In general, people were very critical of this notion. A lot of road improvements would be required, safety of car passengers could be compromised, driving the large vehicles could put significant pressures on driver health and so forth. In parallel with these arguments, there were complaints from people living in remote areas that commercial traffic was damaging their roads and repair work was not keeping up with their needs. The alternative that everyone favoured, in principle at least, was a return to railway transport. However, nearly all of the main lines still in service were in poor condition, so that speed restrictions were the norm, rather than the exception, while the branch lines, which had been closed for many years, had deteriorated to the point they were not worth refurbishing. Unfortunately, no one was prepared to spend the required funds on upgrades!

It seems to me that there are a couple of opportunities, here. Firstly, a rural branch line (or part of one) could be reconstructed as an elevated railway. Then, if that experiment was successful, a section of a main line (preferably a low-lying one where substantial repairs due to the damage to ballast and the occurrence of mud-holes are an immediate requirement) could be replaced by a section of overhead railway. A major advantage in this case is that little, if any, railway closure would be required. Furthermore, as most main lines in Australia still employ ballast as a base, a move to so-called Very Fast Trains, or VFTs will require substantial upgrade work, which will not be necessary on the elevated section. This will already be sufficiently stable, while the trough deck construction will allow a wide range of superelevation, if carriages are fitted with retractable outriggers, which can bear on the trough walls to maintain balance.

From my own personal perspective, I have a profound belief in the superiority of railways as a transport medium for people and goods. They are safer, more economical and, so far as long-distance point-to-point travel is concerned, they are faster  and often more convenient than road transport. There are exceptions, of course, in particular situations:

  • Aeroplanes have higher speeds in the air, but take-off and landing, embarkation and disembarkation and the processing of passengers and goods largely negate this advantage. Internationally, airline travel still has some advantage, but if some remarkable ideas such as the  installation of a maglev train running in a tunnel under the sea ever came to fruition, this situation could change significantly.
  • Local traffic in rural areas and cities rely on a complex network of roads for travel and obviously this cannot be matched by railways. However, many long-distance journeys between settlements are made by car simply to have the convenience of driving around the destination without additional expense. This problem can be solved simply by providing facilities for carrying the car on the train. When we moved from Perth to Melbourne, we travelled on the Indian Pacific for most of the way and our car was simply driven onto a flat wagon and secured. The Monocab designer is also thinking about adding a flat deck for a car to the rear of his vehicles. I have conceived the idea of a wagon with a box like a shipping container which sits on a wagon but can be rotated through 90 degrees, so that the car can be driven straight onto it without any special equipment. At the other end of the box is a passenger compartment equipped with toilet, refrigerator and a microwave. It may also be possible to include a corridor so that these wagons may be included in the body of the train with the travellers sitting in a nearby compartment. This version would be useful if overnight travel is required.

An interesting aspect which has only come up in the exploration of the overhead railway concept is the multiple kinds of traffic which could be accommodated. The normal fast train, driven by a variety of (mostly) renewable resources has been joined by the Monocab and now by the Maglev. If the floor of the troughs was properly designed, it might even be possible to allow appropriately equipped road vehicles to drive along them at times of low-intensity rail traffic.

I believe that these times offer some exciting and interesting possibilities for the railway.  I am just a little sad that I am now retired and not able to take an active role in its regeneration. Still, even an observer might have some ideas to contribute!


About jimthegeordie

I was born in the north of England and am a Geordie. Geordies are celts who are noted for having long bodies with short arms and legs. After working in UK, Africa and Australia as a civil engineer and IT contractor I am now retired and living in a beautiful wine-making area. I am the patriarch of a wonderful family, of whom I am inordinately proud.
This entry was posted in climate change, communications, environment, sustainable population, transport and tagged , , , , , , . Bookmark the permalink.

2 Responses to Elevated Railways: The What, The How And The Why

  1. Dr Shoib says:

    excellent information keep up your good work thanks.

  2. Nice of you to say so, Dr. Shoib. We do appear to have something in common; namely, the restoration of aging and damaged landscapes!

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