Most commuter (or suburban) trains are built to main line rail standards, differing from light rail or rapid transit (metro rail) systems by:being larger
providing more seating and less standing room, for the longer distances involved
having (in most cases) a lower frequency of service
having scheduled services (i.e. trains run at specific times rather than at specific intervals)
serving lower-density suburban areas, typically connecting suburbs to the city center
sharing track or right-of-way with intercity or freight trains
not fully grade separated (containing at-grade crossings with crossing gates)
Compared to rapid transit (or metro rail), commuter/suburban rail has lower frequency, following a schedule rather than fixed intervals, and fewer stations spaced further apart. They primarily serve lower density suburban areas (non inner-city), and often share right-of-way with intercity or freight trains. Some services operate only during peak hours and others uses fewer departures during off peak hours and weekends. Average speeds are high, often 50 km/h (30 mph) or higher. These higher speeds better serve the longer distances involved. Some services include express services which skip some stations in order to run faster and separate longer distance riders from short-distance ones.
The general range of commuter trains' distance varies between 15 and 200 km (10 and 125 miles). Sometimes long distances can be explained by that the train runs between two or several cities (e.g. S-Bahn in the Ruhr area of Germany). Distances between stations may vary, but are usually much longer than those of urban rail systems. In city centers the train either has a terminal station or passes through the city centre with notably fewer station stops than those of urban rail systems. Toilets are often available on board trains and in stations.
Their ability to coexist with freight or intercity services in the same right-of-way can drastically reduce system construction costs. However, frequently they are built with dedicated tracks within that right-of-way to prevent delays, especially where service densities have converged in the inner parts of the network.
Most such trains run on the local standard gauge track. Some light rail systems may run on a narrower gauge. Examples of narrow gauge systems are found in Japan, Indonesia, Switzerland, in the Brisbane (Queensland Rail's City network) and Perth (Transperth) systems in Australia, in some commuter rail systems in Sweden, and on the Genoa-Casella line in Italy. Some countries, including Finland, India, Pakistan, Russia, Brazil and Sri Lanka, as well as San Francisco (BART) in the USA and Melbourne and Adelaide in Australia, use broad gauge track.
Metro rail or rapid transit usually covers a smaller inner-urban area ranging outwards to between 12 km to 20 km (or 8 to 14 miles), has a higher train frequency and runs on separate tracks (underground or elevated), whereas commuter rail often shares tracks, technology and the legal framework within mainline railway systems.
However, the classification as a metro or rapid rail can be difficult as both may typically cover a metropolitan area exclusively, run on separate tracks in the centre, and often feature purpose-built rolling stock. The fact that the terminology is not standardised across countries (even across English-speaking countries) further complicates matters. This distinction is most easily made when there are two (or more) systems such as New York's subway and the LIRR, Metro-North along with PATH, Paris' Métro and RER along with Transilien, London's tube lines of the Underground and the Overground, (future) Crossrail, Thameslink along with other commuter rail operators, Madrid's Metro and Cercanías, Barcelona's Metro and Rodalies, and Tokyo's subway and the JR lines along with various privately owned and operated commuter rail systems.
In Germany the S-Bahn is considered as a train category of its own, and exists in many of the large cities and in some other areas but do have differing service and technical standards from city to city. Most S-bahns typically behave like commuter rail with most trackage not separated from other trains, and long lines with trains running between cities and suburbs rather than within a city. The distances between stations however, are usually short. In larger systems there is usually a high frequency metro-like central corridor in the city center where all the lines converge into. Typical examples of large city S-Bahns include Munich and Frankfurt. S-Bahns do also exist in some mid-size cities like Rostock and Magdeburg but behave more like typical commuter rail with lower frequencies and very little exclusive trackage. In Berlin, the S-Bahn systems arguably fulfill all considerations of a true metro system (despite the existence of U-Bahns as well) – the trains run on tracks that are entirely separated from other trains, short distances between stations, high frequency and uses tunnels but do run a bit further out from the city centre, compared with U-Bahn. A similar network exists in Copenhagen called the S-tog. (where a metro system also exists). In Hamburg and Copenhagen, other, diesel driven trains, do continue where the S-Bahn ends ("A-Bahn" in Hamburg area, and "L-tog" in Copenhagen).
Regional rail usually provides rail services between towns and cities, rather than purely linking major population hubs in the way inter-city rail does. Regional rail operates outside major cities. Unlike Inter-city, it stops at most or all stations between cities. It provides a service between smaller communities along the line, and also connections with long-distance services at interchange stations located at junctions or at larger towns along the line. Alternative names are "local train" or "stopping train". Examples include the former BR's Regional Railways, France's TER (Transport express régional), Germany's DB Regio and South Korea's Tonggeun services.
Regional rail does not exist in this sense in the United States, so the term "regional rail" has become synonymous with commuter rail there, although the two are more clearly defined in Europe.
In some European countries the distinction between commuter trains and long-distance/intercity trains is very hard to make, because of the relatively short distances involved. For example, so-called "intercity" trains in Belgium and the Netherlands carry many commuters and their equipment, range and speeds are similar to those of commuter trains in some larger countries. In the United Kingdom there is no real division of organisation and brand name between commuter, regional and inter-city trains, making it hard to categorize train connections.
Russian commuter trains, on the other hand, frequently cover areas larger than Belgium itself, although these are still short distances by Russian standards. They have a different ticketing system from long-distance trains, and in major cities they often operate from a separate section of the train station.
The easiest way to identify these "inter-city" services is that they tend to operate as express services - only linking the main stations in the cities they link, not stopping at any other stations. However, this term is used in Australia (Sydney for example) to describe the regional trains operating beyond the boundaries of the suburban services, even though some of these "inter-city" services stop all stations similar to German regional services. In this regard, the German service delineations and corresponding naming conventions are clearer and better used for academic purposes.
Sometimes high-speed rail can serve daily use of commuters. The Japanese Shinkansen high speed rail system is heavily used by commuters in the Greater Tokyo Area. They commute between 100 and 200 km by Shinkansen. To meet the demand of commuters, JR sells commuter discount passes and operates 16-car bilevel E4 Series Shinkansen trains at rush hour, providing a capacity of 1,600 seats. Several lines in China such as the Beijing–Tianjin Intercity Railway, and the Shanghai–Nanjing High-Speed Railway, serve a similar role with many more under construction or planned.
The high-speed services linking Zürich, Bern and Basel in Switzerland (200 km/h (120 mph)) have brought the Central Business Districts (CBDs) of these three cities within 1 hour of each other. This has resulted in unexpectedly high demand for new commuter trips between the three cities and a corresponding increase in suburban rail passengers accessing the high-speed services at the main city-centre stations (or Hauptbahnhof). The Regional-Express commuter service between Munich and Nuremberg in Germany go in (200 km/h (120 mph)) along a 300 km/h high-speed line.
The regional trains Stockholm–Uppsala, Stockholm–Västerås, Stockholm–Eskilstuna and Gothenburg–Trollhättan in Sweden reach 200 km/h (120 mph) and have many daily commuters.
Commuter/suburban trains are usually optimized for maximum passenger volume, in most cases without sacrificing too much comfort and luggage space, though they seldom have all the amenities of long-distance trains. Cars may be single- or double-level, and aim to provide seating for all. Compared to intercity trains, they have less space, fewer amenities and limited baggage areas.
Commuter rail trains are usually composed of multiple units, which are self-propelled, bidirectional, articulated passenger rail cars with driving motors on each (or every other) bogie. Depending on local circumstances and tradition they may be powered either by diesel engines located below the passenger compartment (diesel multiple units) or by electricity picked up from third rails or overhead lines (electric multiple units). Multiple units are almost invariably equipped with control cabs at both ends, which is why such units are so frequently used to provide commuter services, due to the associated short turn-around time.
Locomotive hauled services are used in some countries or locations. This is often a case of asset sweating, by using a single large combined fleet for intercity and regional services. Loco hauled services are usually run in push-pull formation, that is, the train can run with the locomotive at the "front" or "rear" of the train (pushing or pulling). Trains are often equipped with a control cab at the other end of the train from the locomotive, allowing the train operator to operate the train from either end. The motive power for locomotive-hauled commuter trains may be either electric or Diesel-electric, although some countries, such as Germany and some of the former Soviet-bloc countries, also use diesel-hydraulic locomotives.
In the USA and some other countries, a three-and-two seat plan is used. However, few people sit in the middle seat on these trains because they feel crowded and uncomfortable. It is said one industrial designer for one of New York City's commuter railroads, Metro-North, told people: "I designed the aisle seat with a half-back and no upholstery, so it will be very uncomfortable to sit there. They'll move in and take the center seat!" (This seating design can also be found on older NJ Transit and Long Island Rail Road rolling stock.)
In Japan, longitudinal (sideways window-lining) seating is widely used in many commuter rail trains to increase capacity in rush hours. Carriages are usually not organized to increase seating capacity (although in some trains at least one carriage would feature more doors to facilitate easier boarding and alighting and bench seats so that they can be folded up during rush hour to provide more standing room) even in the case of commuting longer than 50 km and commuters in the Greater Tokyo Area have to stand in the train for more than an hour.
Currently there are not many examples of commuter rail in Africa. Metrorail operates in the major cities of South Africa, and there are some commuter rail services in Algeria, Kenya, Morocco, Alexandria, Egypt and Tunisia. In Algeria, SNTF operates commuter-rail lines between the capital Algiers and its southern and eastern suburbs. They also serve to connect Algiers' main universities to each other. The Dar es Salaam commuter rail offers intracity services in Dar es Salaam, Tanzania.
In Japan, commuter rail systems have extensive network and frequent service, and are heavily used. In many cases, Japanese commuter rail is operationally more like a typical metro system (with very high operating frequencies, an emphasis on standing passengers, short station spacing) than it is like commuter rail in other countries. Japanese commuter rail also tends to be heavily interlined with subway lines, with commuter rail trains continuing into the subway network, and then out onto different commuter rail systems on the other side of the city. Many Japanese commuter systems operate several levels of express trains to reduce the travel time to distant locations, often using station bypass tracks instead of dedicated express tracks. It is notable that the larger Japanese commuter rail systems are owned and operated by for-profit private railway companies, without public subsidy.
Commuter rail systems have been inaugurated in several cities in China such as Beijing, Shanghai, Zhengzhou, Wuhan, Changsha and the Pearl River Delta. With plans for large systems in northeastern Zhejiang, Jingjinji, and Yangtze River Delta areas. The level of service varies considerably from line to line ranging high to near high speeds. More developed and established lines such as the Guangshen Railway have more frequent metro like service. Hong Kong MTR's East Rail Line and West Rail Line were built to commuter rail standards but are operated as a metro system.
In Taiwan, Western Line in Taipei-Taoyuan Metropolitan Area, Taichung Metropolitan Area, Tainan-Kaohsiung Metropolitan Area as well as Neiwan-Liujia Line in Hsinchu Area is considered commuter rail.
Other examples in Asia include Seoul Metropolitan Subway of which some lines are suburban lines operated by Korail in South Korea.
In Indonesia, the KA Commuter Jabodetabek is the largest commuter rail system in the country, serving Jakarta metropolitan area. It connects Jakarta city center with surrounding cities and sub-urbans in Banten and West Java provinces, including Depok, Bogor, Tangerang, Bekasi, Serpong and Maja. In July 2015, KA Commuter Jabodetabek served more than 850,000 passengers per day, which is almost triple of the 2011 figures, but still less than 3.5% of all Jabodetabek commutes.
Other examples include KTM Komuter in Malaysia, and the Philippine National Railways orange line in Metro Manila, Philippines.
In India, commuter rail systems are present in major cities. Mumbai Suburban Railway, the oldest suburban rail system in Asia, carries more than 7.24 million commuters on a daily basis which constitutes more than half of the total daily passenger capacity of the Indian Railways itself. The Chennai Suburban Railway along with MRTS is another railway of comparison where more than 1 million people travel daily to different areas in Chennai. In Hyderabad, the MMTS mainly transports people from the city centre to HI-TEC city, the city's Information Technology hub. Other commuter railways in India include Kolkata Suburban Railway which is the biggest Suburban Railway network in India covering 348 stations, Delhi Suburban Railway, Pune Suburban Railway and Lucknow-Kanpur Suburban Railway.
In Iran, SYSTRA has done a "Tehran long term urban rail study". SYSTRA proposed 4 express lines which are similar to RER suburban lines in Paris. Tehran Metro is going to construct express lines. For instance, the Rahyab Behineh, a consultant for Tehran Metro, is studying Tehran Express Line 2. Tehran Metro currently has a commuter line between Tehran and Karaj. Esfahan has two lines to its suburbs Baharestan and Fuladshahr under construction, and a third line to Shahinshahr is planned.
Major metropolitan areas in most European countries are usually served by extensive commuter/suburban rail systems. Well-known examples include Beovoz in Belgrade (Serbia), S-Bahn in Germany and German-speaking areas of Switzerland and Austria, Proastiakos in Greece, RER in France and Belgium, suburban lines in Milan (Italy), Cercanías in Spain, CP Urban Services in Portugal, Esko in Prague and Ostrava (Czech Republic), HÉV in Budapest (Hungary) and DART in Dublin (Ireland).
In Russia, Ukraine and some other countries of the former Soviet Union, electrical multiple unit passenger suburban trains called Elektrichka are widespread.
In Sweden, electrified commuter rail systems known as Pendeltåg are present in the cities of Stockholm and Gothenburg. The Stockholm commuter rail system, which began in 1968, is similar to the S-Bahn train systems of Munich and Frankfurt such that it may share railway tracks with inter-city trains and freight trains, but for the most part run on its own dedicated tracks, and that it is mainly used to transport passengers from nearby towns and other suburban areas into the city centre, not for transportation inside the city centre. The Gothenburg commuter rail system, which began in 1960, is similar to the Stockholm system, but does fully share tracks with long-distance trains. Other train systems that are also considered as commuter rail but not counted as pendeltåg include Roslagsbanan and Saltsjöbanan in Stockholm, Östgötapendeln in Östergötland County, Upptåget in Uppsala County and Skåne Commuter Rail. Skåne Commuter Rail (Pågatågen) in Skåne County acts also as a regional rail system, as it serves cities over 100 km (62 miles) and over one hour from the principal city of Malmö.
In Norway, the Oslo commuter rail system is the largest, which mostly shares tracks with more long-distance trains, but also runs on some local railways without other traffic. Oslo has the largest commuter rail system in Scandinavia measured as line lengths or number of stations. But some lines have travel times (over an hour from Oslo) and frequencies (once per hour) which are more like regional trains. Also Bergen, Stavanger and Trondheim have commuter rail systems. These have only one or two lines each and they share tracks with other trains.
In Poland, commuter rail systems exist in Tricity, Warsaw, Cracow and Katowice urban area. There is also a similar system planned in Wrocław.
In the United States, Canada, Costa Rica, El Salvador and Mexico regional passenger rail services are provided by governmental or quasi-governmental agencies, with a limited number of metropolitan areas served.
Examples include an 899 km (559 mi) commuter system in the Buenos Aires metropolitan area, the 225 km (140 mi) long Supervia in Rio de Janeiro, and the Metrotrén in Santiago, Chile. Another example is Companhia Paulista de Trens Metropolitanos (CPTM) in Greater São Paulo, Brazil. CPTM has 93 stations with six lines, numbered starting on 7 (the lines 1 to 6 belong to the São Paulo Metro), with a total length of 260.8 kilometres (162.1 mi).
Major cities in Australia have suburban railway systems in their metropolitan areas. As with Japanese suburban railways or Germany's and Switzerland's S-Bahns, these Australian networks have far more frequent services and far higher ridership per capita than US 'commuter rail' in the usual sense of the term. To some US observers these networks may appear to operate as commuter/metro hybrids, however, they are simply the result of full utilisation of the available track capacity in the core of the suburban rail network, this being fed from multiple feeder lines. This is particularly so in Sydney and Melbourne, where headways on many lines in the core of the network reach 3–5 minutes in peaks and 10–20 minutes off peak (about 18 hours a day) and enter an underground loop for passenger distribution in the city centre; and where ridership per capita exceeds the sum of metro and commuter rail in comparable North American urban areas such as Toronto, Boston or the San Francisco Bay Area. All systems, however, are based on established main line rail systems, and track sharing with inter-city and freight services on parts of the network inhibit higher frequencies on some tracks. They are sometimes erroneously referred to as heavy rail, a different mode of public transport.
The main systems of commuter rail in Australia include:Sydney Trains in Sydney
Metro Trains Melbourne in Melbourne. ("Metro" in this case being an abbreviation of "metropolitan", to distinguish these services from regional trains under the V/Line brand.)
Queensland Rail City network in Brisbane.
Transperth Trains in Perth.
Adelaide suburban railway in Adelaide.
New Zealand has two commuter rail systems, one using 25,000 V AC in Auckland and the other one using 1,500 V DC in Wellington (formerly operaterd by Tranz Metro).