Investing for fundamental change
Investments linked to fundamental changes in railway capacity are more complex and difficult to resolve. Often, when railways need to adapt to rising traffic volumes and new requirements for rail services, substantial revision of existing railway technology is required, which may take many years to fully implement and many more years to fully realize benefits. That is because, based on their original fundamental design parameters—capacity, budget, services—most railways were carefully designed and engineered to maximize utility as a system. Consequently, it is not possible to change only one engineering parameter because railways are a tightly integrated system of engineering solutions.

Changing gauge
Some railways believe they are constrained by gauge, normally, too narrow rather than too wide. Changing railway gauge sometimes makes sense. For example, if branch line gauges differ from most of the network, if significant interchanges occur between the main and branch lines, and if branch lines have substantial growth potential, they should be connected to the main network and converted to the main-line gauge. In Australia, several state railways were built with a different gauge but recently, segments of narrow gauge were converted to standard gauge to provide a continent-wide standard-gauge railway line. Some grain branches were converted to standard gauge, but a network of narrow gauge mineral lines remained narrow gauge.

India has three gauges—most of the main line is built to Indian broad gauge, and some branches are standard or narrow gauge. Over time, Indian Railway has converted some narrow and standard gauge lines to broad gauge.

There is rarely a good reason to change gauge on an active railway because changing an entire system is an extremely expensive option that must be justified by a business case. Not only must railway tracks be replaced between stations, and through marshaling yards, sidings, storage, workshops, and depots, but also all rolling stock must be replaced to match the new gauge. Changing gauge can be considered for branch lines, for a railway that is completely worn out, or for a railway that has closed and is to be repurposed.

A common misconception is that narrow gauge railways must adopt a wider gauge to increase capacity. But narrow gauge railways can increase axle loads, carry heavy traffic volumes, or even handle moderately high-speed services. Narrow and Cape gauge railways in Argentina, Brazil, and South Africa demonstrate that massive volumes of bulk commodities can be moved on narrower gauge railways. In Australia, a high-speed tilting train commonly operates passenger lines at 160 kph over Queensland Railways’ Cape gauge. In Japan too, mini-Shinkansens operate at higher-speeds on Cape gauge track to connect with main Shinkansen services.

New special-purpose high-speed or heavy-haul railway lines dedicated to moving output from a mine to a port can be built using a gauge that differs from the national railways. The best alternative for high-speed and heavy-haul rail services is standard gauge, commonly used by most railways worldwide, so competitive bidding will likely yield a lower price.

Image of Automatic Coupler Coupler type and strength
Some railways rely on old coupling technology to assemble a train. Older coupling systems use hooks and chains, links and pins, or buffers and chains, so coupling freight and passenger equipment must be done by hand, each car individually. Old coupling technology is also weaker, limiting train size to quite short or quite light trains. Modern railways replaced old systems with stronger automatic couplers (photo at left) that are more efficient and much stronger. Even though couplings can be made automatically, brake system air hoses still require manual connection between each rail car before trains can depart.

Changing to stronger automatic couplers can significantly increase financial performance. Higher safety and operational flexibility mean that railways can run fewer trains with heavier loads, thereby increasing capacity without building a new line or double tracking an existing railway line. Modern technology is also more reliable and less expensive to maintain.

Usually, coupling systems are changed incrementally to avoid wasting useful capacity from existing rolling stock. Rolling stock used in unit-train type services can be changed first—train sets that carry containers, coal or ore, or passenger equipment—to avoid changing all rolling stock coupling systems at once. Typically, this requires converting some locomotives to haul trains with new coupling technology, and retaining some locomotives for use with old coupling systems. Incremental change will necessarily introduce some temporary inefficiency in equipment utilization since rolling stock fleets must be segregated into different pools. The best time to change coupling systems is when new bulk or passenger train-sets are purchased for specific services.

When modern coupling systems are introduced, new infrastructure investment may be required to accommodate changes in train size and weight. Since new coupling systems allow longer and heavier trains, longer sidings and wider signal spacing may be required. In addition, marshaling yards, customer sidings, and other infrastructure must be adapted and railways may need new locomotives to fully exploit the potential of increased train weight permitted by new coupler systems. All these investments must be part of a strategy and investment plan.

Axle loads
Many railways were built to accommodate set axle loads for freight cars and locomotives, calculated as tons per axle; raising this limit is an effective way to increase rail system capacity.

However, despite adequate infrastructure, many railways are reluctant to operate at the higher end of axle load technical capacity for several reasons: rail wears out faster; accidents can be more damaging; and many bridges and culverts were designed for lower load limits. Sometimes rolling stock needs subtle changes in bogie suspension systems (different spring rates) to minimize impacts from higher axle loads.

Technical factors that limit axle loads include type, size, and spacing of sleepers or crossties; rail weight or size (usually measured in kilograms per meter); thickness of roadbed sections; rail metallurgy; and bridge and culvert designs—changing axle loads can require significant investment.

Some railways have low axle load limits of 12.5-tons/axle. Typical heavy-duty railways have at least 25-tons/axle limits; North American railways have 32.5-tons/axle limits (metric measure), a level common to heavy-haul railways in many countries. Recently, an Australian company built a specialized mineral railway designed for 40-tons/axle loads, which is currently the upper load limit for railways due to rail metallurgy limitations. Initially, the railway will operate at 32.5-ton/axle load limits to permit rails to become work-hardened and infrastructure to settle before increasing to full design capacity.

Railways around the world with similar rail and sleeper specifications have axle load limits ranging from 22.5 to 32.5 tons/axle. For example, in Russia, most main rail lines use R65 rail (65 kg/m; 131 lbs/yd), large concrete sleepers on good spacing (1,660 sleepers/kilometer), but axle loads were limited to 22.5-tons/axle. Recently, Russian railways began allowing 25-tons/axle equipment on some lines and later plans to gradually move to 27.5-tons/axle.

Image of Bridges India is similar, with relatively heavy rail, closely spaced modern concrete sleepers, and a 22.5-ton axle load. Recently, without substantial infrastructure changes, India began allowing 25-tons/axle equipment on some lines.

Most railways can increase axle load limits by introducing only small changes to infrastructure. For example, many railways have discovered that only small investments are needed to strengthen bridge abutments and span members, or that minor speed restrictions will allow heavier axle loads to pass over bridges. In other cases, raising axle load limits may require substantial investment to strengthen or replace old structures, such as the 1896 Armenian cast-iron bridge (at left). Exceptionally large structures engineered for design load limits at the time and limited by construction costs may need more extensive investments. The 3.7 km Dona Ana Bridge over the Zambizi River at Sena, Mozambique (at left) needed substantial strengthening.

Increasing axle loads significantly boosts railway capacity because higher axle loads increase freight car carrying capacity almost directly, without increasing the weight of the freight cars very much, if at all. For example, increasing axle load limits from 22.5 to 25 tons (about 10%) increases the carrying capacity of a fully loaded freight car from about 68-tons to 78-tons (a 15 percent increase). Second, increasing locomotive axle loads contributes directly to increased hauling power, which is directly related to locomotive weight, assuming no change in locomotive horsepower or in wheel/rail friction control systems. Increased locomotive weight results in the ability to haul longer and heavier trains.

Axle load increases can result in heavier trains of the same length, which means that railways do not have to invest in longer sidings and new signal systems to achieve substantial capacity increases.

Image of Loading Gauge Loading gauge
Loading gauge defines maximum vehicle size the railway line can accommodate. Loading gauge is determined by the size of tunnel openings, bridges, and passenger platforms or loading docks adjacent to the track. Increasing loading gauge can permit the use of larger freight and passenger cars significantly increasing capacity and reducing the number of trains needed to move the same amount of traffic.

Today, most loading gauge increases are to introduce bi-level passenger cars and double stack container trains. Commonly, loading gauge increases are designed is needed to replace through-truss bridges, to lower tracks in tunnels, and increase vertical clearances for highway and pedestrian overpasses. Bi-level passenger equipment and double-stack container equipment can reduce the number of trains needed to move the same number of traffic units, thus increasing capacity. Increases in permitted height can accommodate larger/taller box cars, and multi-level auto carrier equipment, which opens a new market for some railways and increases the freight traffic volume that can be carried, thus increasing railway capacity.

Often, railways combine increases in axle load and loading gauge to modernize and substantially increase capacity.

Double track
Originally, most railway lines were built using a single track. Trains moving in opposite directions on a single track railway line meet at stations or at passing sidings or loops. Usually, less time-sensitive train waits in the passing siding or station track for the other higher-priority train moving in the opposite direction to pass. This process time and energy — the waiting train must first slow down to move into the siding, come to a complete stop, wait until the superior train passes, then accelerate until it attains track speed.

Typically, line capacity is measured by the maximum number of trains (or train pairs — one in each direction) that can operate over a line each day. On single track lines, line capacity is limited by the number of available passing loops, train composition, train control and signaling systems, train speeds, and the structure of train schedules. Thus, on a single track line, more trains typically mean more train delays. Eventually, all passing loops are filled and no more trains can enter the line until trains on the line exit.

As the number of trains increase, more passing loops must be added to increase line capacity. Some passing loops can be lengthened to become sections of double track so the inferior train (the one taking the siding) can move along the extended siding without having to come to a complete halt. Usually, signal systems are upgraded as a part of capacity improvement investments to fully exploit the passing loops. Railways can further increase capacity by increasing train speeds, or by raising the number of traffic units on each train with higher axle loads and/or loading gauge. When all these measures have been taken, any additional capacity will require double tracking.

Double tracking is usually the option of last resort to increase capacity since it essentially doubles infrastructure investment and maintenance costs. Often, railways will double track only the rail line sections that are cheapest to build and leave the expensive sections as single track, especially bridges, tunnels, and large cuts.

Signal and train control systems
Railway signaling is a critical element of infrastructure safety and capacity. Signals indicate when trains should slow down, stop, or go. Most trains travel at the posted track speed limit and since railway trains weigh 1,000 to 20,000 tons, they require considerable time to slow and stop. Most railway signal systems are meant to regulate traffic flows, not indicate travel speeds. Train control systems work with signal systems to shift trains from one track to another. The most basic systems issue written orders to departing trains on how to navigate the track ahead. For example:

“Proceed to the passing siding at kilometer 10.5; wait on the main line to meet train number XYZ which will take the siding. When clear, proceed to the passing siding at kilometer 35.7, take the siding and wait for train number ABC to pass on the main. When clear, proceed to destination.”

Image of Semaphore Signal and Central Dispatcher Control Panel In such rudimentary train control systems, train meets can take a long time. The train crew may have to stop the train, manually throw track switches to enter the siding, and then, when clear, throw them back, and repeat this procedure on departure from the siding.

In somewhat more advanced systems, switches are controlled remotely (either mechanically or electrically). Station staff throw the switch to the siding, which changes wayside signals in advance of the siding to indicate to the advancing train that it will enter the siding. The signals indicate to drivers that they need to slow to approach speed and prepare to stop. The signal indicates to the train in the opposite direction that it can proceed. Semaphore systems are examples of this type signal system. These systems are faster than train order systems but have little flexibility; they can only affect train speed and control at staffed stations.

In more advanced systems, often called ‘automatic block signal’ system (or ABS) electrical circuits are embedded in the track to detect trains. The system automatically aligns passing loop switches and signals to correctly signal trains in both directions. Signals controlling sidings must be connected to one another because train departures from a station are not permitted if a train is in the block of track ahead. For distant passing sidings, intermediate signals are used to permit trains to operate at track speed until the approach distance to the next controlled siding.

An ABS signaling system does not prioritize trains—the first train to arrive at the siding where trains will meet is directed to take the siding. To exercise greater control over train movements, railways developed centralized train control systems (CTCs). These systems allow a centralized dispatcher (now sometimes a computer control program) to allow faster trains to pass slower trains moving in the same direction, to allow trains to stay on the main line if they exceed the siding length, or to allow higher priority trains to keep to the main lines with as few stops as possible.

The ABS and CTC systems provide several safety advantages. They use electrical track circuits to detect trains and train speeds. These track circuits also detect broken rails or wash-outs and stop trains before passing the danger area. The electronic controls are fail-safe and interlocked so a switch cannot be thrown under a train or allow two train paths to cross. If any part of the system fails, signals automatically protect trains from running into each other.

Double track segments are usually directional (up trains on one track, down trains on the other). CTC systems can be designed for reverse running so that trains can use either track to move in either direction, increasing flexibility and capacity, and allowing work crews to perform maintenance on one track while trains move along the other. The CTC systems permit fast trains to pass slow trains, and allow some trains to stop or serve customers on the main line while trains move along the opposite track.

In traditional ABS and CTC systems, the railway line is segmented into signal control blocks. Block length is determined by calculating the stopping distance of the heaviest or fastest train—the longest stopping distance—and then fixed by track circuit design. The systems permit trains to occupy a block, and at least one empty block is kept between trains. The number of blocks between trains is determined by how many aspects are used in the signal system. Typically, there are three aspects (for example, red, yellow, green) but systems in the busiest lines can have four or more, which facilitate finer control of speed and allow overlapping blocks so that trains can follow at shorter distances.

The latest and most advanced signal systems dispense with wayside signals and discrete signal aspects. Instead, they provide digitally controlled train speed, and base train spacing on the physical characteristics of the infrastructure and particular train, adjusting train speeds to maintain stopping distances between trains. More advanced signal systems provide train ‘pacing’ or speed information that permits the minimum amount of slowing when trains meet, thus reducing energy consumption and maximizing line capacity.

Successive advancements in signal and train control systems increase line capacity, safety, and train speeds, and reduce energy consumption. Of course, as systems become more sophisticated, they also become more expensive.

Originally, railway trains were hauled by steam locomotives, fueled with wood, coal, or oil.122 Diesel-electric and diesel-hydraulic locomotives were developed in response to steam locomotive shortcomings, such as the need for frequent stops to refuel and take on water. As engineering improved, diesel engine technology developed higher horsepower locomotives. Thanks to improvements in wheel-slip controls and computer control systems, modern diesel-electric locomotives are highly productive and energy-efficient.

Image of 3kV-DC Overhead Catenary, Georgia To reduce dependence on diesel fuel and provide higher capacity operations, railways turned to electrification, usually using overhead catenary systems to deliver electricity. Electric locomotives can have higher power density—more horsepower or kilowatts per ton of locomotive—which can haul trains at higher speeds and up steeper grades than diesel locomotives. Generally, electric locomotives require fewer maintenance inputs and were once considered more reliable. Modern diesel-electric locomotives are now as reliable as electrics and can provide the similar levels of tractive effort – for high speeds, electric locomotives are advantaged.

Electrification is essential for high-speed train operations of more than 160-kph or 100-mph. Electrification is useful in high-density operations where train acceleration is important, such as commuter passenger systems; and where diesel fuel is too expensive or scarce.

Electrification is expensive; it requires substations and overhead catenary structures along the railway, and infrastructure maintenance costs are higher. Thus, electrification is rarely financially feasible unless traffic densities are at least 40 million gross tons per year, or for high-speed and commuter services.

Electric railways are substantially more environmentally friendly and have fewer carbon emissions than diesel-electric railways if the electricity is generated by renewable energy or nuclear power. If the electricity is generated in a coal-fired plant, electric railways have about the same environmental impact as diesel-electric powered railways.

Information systems
Information systems are among the most important investments for commercial railways, particularly for revenue, cost accounting, and general ledger systems that have a level of detail that facilitates accurate tracking of railway costs and revenues. Railways must be able to analyze complex data on costs, production statistics, and revenue along several dimensions. Some examples: for passenger services, railways must analyze revenue by ticket type, origin, destination, and time of day; and costs by carriage type, route, time-of-day, and day-of- week; for productivity, railways must analyze number of passengers, passenger kilometers, train kilometers, carriage kilometers. Freight data are equally complex and must include tons, ton-kilometers, disaggregated by commodity, customer, type of freight car, tariff type, origin and destination, and so on. This kind of analysis requires computers and dedicated systems.

Pre-computer-era railway systems may keep some of these data, but usually highly aggregated, manually maintained, and unavailable on a timely basis. Without modern costing systems, cost data are not available in the detail needed to determine costs of specific services, or even entire lines of business, without resorting to large-scale allocation using highly aggregated data.

Commercial railways must analyze traffic, revenue, and costs across many dimensions and must be able to develop detailed income and profit and loss statements, at least for major lines of business. Railway asset holdings, lifespan, cost, and condition must be tracked, usually in asset registers or other types of systems that inform balance sheets.

These capabilities are now readily available in off-the-shelf packages that can be customized by language and input type. Most railways need new location-, function-, and responsibility-based cost accounting systems that track detailed costs. Railways need revenue accounting systems such as ticketing systems that collect data with sufficient detail to provide revenue by class of service and by train number and date. For freight traffic, railways need waybilling systems that track revenue by customer, commodity, car type, origin and destination, and contract agreement. Revenue accounting systems can often be call-center based, eliminating many station agents and local clerical staff.

All of these systems inform railway management and allow operations personnel to manage costs and services more effectively. Railways need other operational management systems to monitor and schedule rolling stock maintenance by unit number, record repairs made under warranty, analyze infrastructure degradation to optimize maintenance scheduling, program train drivers to better manage duty times, and a myriad of other operational and management activities.

Usually, required information systems rely on high-quality communications systems to transmit data across the railway network. Often, communications systems are commercially available but many railways have installed fiber optic systems along their lines, using some capacity themselves and selling the balance to other businesses or to national telecommunications companies, including cell phone operators.

Generally, information systems and communications investments yield high returns and facilitate intelligent implementation of reform programs using adequate management information.


122 There were some early horse-pulled railways. Other early railways were pulled by cables.
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