Electric traction and urban transport: trams, tubes, suburban railways and the cities they built

Before electricity, cities were limited by how far people could walk. Horse-drawn omnibuses and trams helped, but horses were slow, expensive to feed and stable, and produced vast quantities of manure. Steam locomotives worked on main lines but were dirty, noisy and dangerous in crowded streets and tunnels. Cities were dense, crowded and small by modern standards, and most people lived within walking distance of their work.

Electric traction changed that within a generation. From the late 1880s, electric street railways spread rapidly through cities in North America, Europe and Australia. Electric underground railways made deep tunnels practical. Suburban rail lines were electrified, allowing faster and more frequent services. People could live further from work, and new suburbs grew along tram and train lines. The technical choices made in those decades, from voltages and gauges to whether to keep or remove tram networks, still shape cities today.

This article traces, in general terms, how urban transport moved from horses and cables to electric trams, underground railways and electrified suburban networks, Australia’s distinctive experience, and the lessons for infrastructure, standards and long-lived investment decisions. It is a general historical overview.

Horses, omnibuses and the limits of muscle

Horse-drawn omnibuses appeared in many cities in the early nineteenth century, and horse trams running on rails followed. Rails reduced rolling resistance, so a horse could pull a larger, smoother vehicle. But a horse could work only a few hours a day, so operators needed many horses for each tram. Feed, stabling, veterinary care and the disposal of manure were major costs, and epidemics of equine disease could cripple services. Horse transport also limited speed, and with it the distance people could practically travel.

Cable trams

One answer was the cable tram. A continuous steel cable ran in a slot beneath the street, driven by a stationary steam engine in a powerhouse. Trams gripped the moving cable to move and released it to stop. Andrew Hallidie’s cable car line in San Francisco opened in 1873, and cable trams spread to many cities, particularly where hills defeated horses.

Melbourne built one of the most extensive cable tram networks in the world from 1885, and cable trams ran there until 1940. Cable systems were clean and quiet in the street, but they had disadvantages. Every cable ran at a fixed speed, a single cable break stopped every tram on the line, and much of the engine’s power was spent moving the cable itself. Building the cable conduits under the streets was expensive.

Electric street railways

Electric trams solved most of these problems. A motor on each vehicle drew power from overhead wires or a conductor rail, so each tram could be controlled independently, and power was used only when it was needed. Werner von Siemens demonstrated an electric railway in Berlin in 1879, and several cities experimented with electric trams in the 1880s.

The breakthrough came in 1888, when Frank Sprague’s electric street railway system in Richmond, Virginia, entered service with a sizeable fleet on hilly routes. It combined reliable motors, gearing, a spring-loaded trolley pole collecting current from an overhead wire and a power station. Its success led to a rapid conversion of horse and cable systems to electricity across the United States and then around the world.

Electric trams created the streetcar suburb. Developers often built tram lines to sell land, and suburbs spread along the routes. The pattern of many older cities, with commercial strips along former tram routes and residential streets behind them, dates from this period.

Powering the network

Electric tramways needed their own power. Early operators built dedicated power stations, often coal-fired, with steam engines driving DC generators, and fed the overhead wires through cables and, as networks grew, through substations spread along the routes. The tram company was therefore in the electricity business as well as the transport business. In many cities, tramway power stations were among the first large electricity supplies, and street lighting and private customers were sometimes connected to them.

Traction loads are demanding. Many trams accelerating at once draw large currents, and the load swings constantly through the day. Engineers learned to size substations for peaks, to manage voltage drop at the ends of long lines and to deal with currents returning through the rails, which could corrode nearby buried pipes if not controlled. These problems, of peak demand, distribution losses and side effects on neighbouring infrastructure, recur in every electrical system that grows quickly.

Going underground

Steam trains had run underground in London since 1863, when the Metropolitan Railway opened in shallow cut-and-cover tunnels, but smoke made the tunnels unpleasant. In 1890, the City and South London Railway opened as the first deep-level underground railway worked by electric trains, running in tunnels bored well below the streets. Electric traction made deep tunnels practical, and underground railways spread to other major cities.

Sprague made another contribution in the 1890s: multiple-unit control, which allowed motors distributed along a train of several cars to be controlled together from a single driving position. Multiple units could accelerate quickly, run in either direction without turning a locomotive around and be lengthened or shortened to match demand. They remain the standard for suburban and metro trains.

Signals, timetables and capacity

Running frequent electric trains through tunnels and busy junctions required reliable signalling. Railways developed track circuits, which detect a train by the electrical connection its wheels make between the rails, and automatic signals that clear only when the section ahead is empty. Automatic train stops could apply the brakes if a train passed a red signal. These systems allowed trains to run close together safely, which is where much of an urban railway’s capacity comes from. Later generations of signalling, using computers and radio, aim to let trains run closer still. The lesson for any operation is that capacity often depends less on the speed of each vehicle than on how safely and closely the whole system can be controlled.

Trolleybuses and motor buses

Some cities adopted trolleybuses, rubber-tyred buses powered from twin overhead wires, which needed no rails and could pull into the kerb. Several Australian cities operated trolleybuses in the mid-twentieth century before replacing them with diesel buses. Motor buses steadily improved, and by the middle of the century they offered flexibility and low capital cost that electric systems with fixed infrastructure could not match on lightly used routes.

Choosing the current: a second contest

As traction spread, engineers faced a choice similar to the earlier contest between direct and alternating current for electricity supply. Traction motors of the time worked best on direct current, so urban tramways and many suburban railways used DC, typically at around 600 volts for trams and higher voltages for railways. DC, however, needed closely spaced substations because of losses over distance.

For long main lines, alternating current at higher voltages was attractive because it could be transmitted further. After the Second World War, systems using 25,000 volts AC at the standard mains frequency, developed notably in France, proved economical and spread widely for new main-line electrification. Many countries now operate a mixture of systems, and trains that cross between them need equipment for more than one. As with railway gauges, early choices became long-lived standards.

Electrifying Australia’s cities

Australian cities followed the international pattern with local variations.

• Melbourne replaced its cable trams with electric trams and kept its tram network when many other cities removed theirs. Today it is often described as the largest urban tram network in the world. Melbourne’s suburban railways began electric operation in 1919, using 1,500 volts DC.
• Sydney built a large electric tram network in the early twentieth century, but replaced it with buses, and the last trams ran in 1961. Sydney’s suburban railways were electrified from 1926, also at 1,500 volts DC. Light rail returned to Sydney’s streets in later decades at considerable cost.
• Brisbane began electric suburban services in 1979, using 25,000 volts AC.
• Adelaide retained a tram line to Glenelg and later extended it, while its suburban railways remained largely diesel for many years before partial electrification.

The contrasting decisions in Melbourne and Sydney show how infrastructure choices that seem economical at one time can look very different decades later. Removing trams saved money on track renewal and allowed more flexible bus routes, but once tracks and reservations were gone, restoring rail was expensive.

What electric traction offered

Electric traction delivered advantages that kept it attractive for over a century:

• No emissions at the point of use, which made tunnels and crowded streets practical.
• High acceleration, which suits services with frequent stops.
• Regenerative braking, in which motors act as generators to return energy to the supply, reducing consumption.
• Lower maintenance of electric motors compared with steam or diesel engines.
• Flexibility of energy source, since electricity can be generated from any fuel or renewable source.

Its main disadvantage is the high fixed cost of overhead wires, substations and power supply, which pays off only on routes with enough traffic. The selecting electric motors and drives article explains how similar trade-offs apply to motors in industry.

Lessons for engineers and businesses

Infrastructure shapes behaviour for generations

Tram and train lines decided where suburbs grew and where shops located. Decisions about plant layout, utilities and systems shape how a business operates long after the people who made them have moved on.

Fixed costs need volume

Electrification pays where traffic is heavy. Any investment with high fixed costs and low running costs needs enough use to justify it, and the forecast of that use deserves careful scrutiny.

Standards outlive their reasons

Voltages chosen for the motors of the 1900s still govern networks today. Before choosing a standard, consider how long it will last and whether it will connect with others.

Removing an asset is hard to reverse

Sydney’s tram removal saved money in the short term and cost much more to partly reverse. Selling, scrapping or abandoning infrastructure, corridors or capabilities can foreclose options that later become valuable.

Recover wasted energy

Regenerative braking returns energy that would otherwise be lost as heat. Many industrial processes waste heat or motion that could be recovered.

Single points of failure matter

A single cable break stopped a whole cable line; independent electric trams avoided that. Designs that isolate failures keep the rest of the system running.

A worked example

This is an illustrative example. The business and figures are hypothetical.

A manufacturer is building a new production hall. The current plan includes underground conduits sized for today’s equipment. The electrical contractor points out that adding larger conduits and spare pits now, while the slab is open, would cost about $4,000 extra. If more capacity were needed later, for example for electric forklifts, an induction furnace or rooftop solar with batteries, cutting the slab, trenching, installing new conduits and reinstating the floor would cost an estimated $30,000 and interrupt production for several days.

The owner treats the spare conduits like a tram corridor kept in reserve: a modest cost now to keep a valuable option open. Even if there were only a one-in-three chance of needing the capacity in the next ten years, the expected cost of retrofitting would be about $10,000, well above the $4,000 premium, before counting the disruption. The spare conduits are installed and recorded on the as-built drawings so that future staff know they exist.

How this applies to a small Australian business

• Treat layouts and utilities as long-lived decisions that shape operations for decades.
• Test whether volume justifies high fixed-cost investments.
• Keep options open cheaply where future needs are plausible, such as spare capacity in services.
• Think carefully before removing assets or corridors that would be costly to restore.
• Look for energy you could recover, such as waste heat or braking energy.
• Avoid single points of failure in critical systems.

Common mistakes

• Judging infrastructure only on first cost. Lifetime costs and options matter more.
• Assuming today’s demand will stay the same. Cities and businesses grow in unexpected directions.
• Choosing an isolated standard that cannot connect with others.
• Losing records of spare capacity, so that later teams cannot use it.

Frequently asked questions

Why did many cities remove their trams? Buses were flexible, required no track and were cheaper to introduce, while ageing tram tracks and vehicles needed expensive renewal. Growing car traffic also made trams in mixed traffic slower. Many cities later regretted the loss of reserved corridors and rebuilt light rail.

Why do some railways use DC and others AC? Early traction motors suited DC, so many urban systems adopted it and kept it. AC at high voltage became economical for long main lines later. Changing an established system is expensive, so both remain in use.

Questions to ask

• Which of our infrastructure decisions will still shape the business in twenty years?
• Do our high fixed-cost investments have enough expected use to pay off?
• Which assets or options would be expensive to restore if we removed them?
• Where are we wasting energy that could be recovered?
• What single failures could stop our whole operation?

Bringing it together

Electric traction freed cities from the limits of walking and horses. Cable trams, electric street railways, deep electric tubes, multiple-unit trains and electrified suburban railways transformed where people lived and worked, and Australian cities followed with their own choices: Melbourne kept its trams, Sydney removed them, and voltages chosen a century ago still run. The railways and the break of gauge and from telegraph to grid articles show the same pattern of long-lived standards and networks. For any business, electric traction teaches that infrastructure shapes behaviour for generations, fixed costs need volume, standards outlast their reasons and removing an asset is often harder to reverse than keeping it.

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Source: KEVOS editorial notes. Examples and figures in this article are illustrations. This article is a general historical overview.