The length of a train, including the longest trains, may be measured in number of wagons (for bulk loads such as coal and iron ore) or in metres for general freight. Train lengths and loads on electrified railways, especially lower voltage 3000 V DC and 1500 V DC, are limited by traction power considerations. Drawgear and couplings can be a limiting factor, tied in with curves, gradients and crossing loop lengths.
Conventional freight trains can average nearly 2,000 metres. Freight trains with a total length of three or four times that average are possible with the advent of distributed power units, or additional locomotive engines between or behind long chains of freight cars (referred to as a "consist"). These distributed power units enable much longer, heavier loads without the increased risks of derailing that stem from the stress of pulling very long chains of train-cars around curves.
- Rail gauge: 1,435 mm (4 ft 8 1⁄2 in) except where shown.
- Rio Tinto—29,500 tonnes of iron ore—2.4 km, three locomotives
- BHP Billiton iron ore typically 336 cars, 44,500 tonnes of iron ore, over 3 km long, six to eight locomotives including intermediate remote unit
- Leigh Creek coal—2.8 km, 161 wagons and 2 locomotives.
- Cane tramway - 75 wagons (610 mm (2 ft) gauge) 
- Daqin Railway coal trains—20,000 t, 3.2 km, 210 wagons
- Mauritania—3 km—iron ore from Zouérat—trains lurch violently when accelerating or braking
- Indonesia (proposed)
- South Africa
- 4200 m - Canada - double-stack container trains reaching 4200 m are regularly operated by Canadian National Railway system wide with distributed power diesel electric locomotives. General cargo trains are limited to 3700 m, and bulk trains are limited to 3000 m but up to 20,700 tons
- 3658 m – United States - Trains are limited by air brake capability. electronically controlled pneumatic braked (180 wagons) – AAR Standard S-4200.
- 1800 m – Australia—Parkes–Perth–Adelaide–Darwin—(limited by 1800 m crossing loops)
- 1524 m - France - intermediate loco - trial 
- 1500 m – Australia—Adelaide–Melbourne–Sydney–Brisbane—(limited by 1500 m crossing loops; some loops to be extended to 1800 m)
- 1500 m – UIC standard double length train
- 1222 m - The Bangalore–Dharmavaram goods train (India)—The train runs between Bangalore and Dharmavaram almost every day. There is no stop for this train, and there is no railway station on this route which can accommodate the whole train on a single track or platform. So all the Superfast, Express trains including the longest passenger train the 31-coacher Gomti express is sent to the loop line.
- Indian Railways term this as increased vehicle length (IVL). This reduces the traffic in this single-lined region; two goods train attached back to back, each train is led by two diesel electric locomotives.
- 1000 m
- 835 m—In Denmark and to Hamburg, Germany; 2 locos and 82 waggons.
- 800 m—RVR in East Africa (Kenya–Uganda) to introduce longer trains, which needs longer crossing loops.
- 750 m – Normal for mainlines in several countries in Europe.
- 750 m – UIC standard single length train
- 400 m – New South Wales steam era, where lengths also limited by practical length of crossing loops mechanically operated from signal boxes.
- Australia – up to 99 coaches (approximately 1.2 km) on The Ghan
- Japan - Tōkaidō Shinkansen N700 16-car trainset 404 m
- The Netherlands – up to 15 coaches (five 3-coach NS Intercity Materieel trains combined) – 403 m
- Sweden – 17 coaches (26.7 m each plus two Rc locomotives at 15.4 m) – 484 m between Stockholm and Luleå. Sometimes charter trains are longer than that, e.g. 22 coaches, 530 m on 24-25 Febr 2012.
- Germany – two ICE 3 trains combined – 402 m
- France – two TGV Atlantique trains combined – 476 m
- United Kingdom, Belgium, France – Eurostar / British Rail Class 373 (20-car multiple unit) – 394 m
- United States — Auto Train between Lorton, Virginia, and Sanford, Florida — up to 50 cars. 4 or 5 coaches, 1 lounge, 3 diners, 6 sleepers, one transition sleeper and up to 35 autoracks.
- United States - Ringling Bros. and Barnum & Bailey Circus trains - longest privately operated passenger trains in the world at nearly sixty cars each. Two trains, the Red unit and the Blue unit, tour the country in an overlapping two-year cycle. Each circus train consists of around 40-45 passenger cars with dorm rooms for the circus performers and crews, four animal cars usually placed at the front of the train for a smoother ride, a dining car referred to as the "pie car," a generator car to provide power to the train, two merchandise boxcars and 15-20 flatcars carrying circus vehicles and containers.
- India - 24-coach trains are standard for most popular long distance services, which translates to approximately 600 meters per train.
- Canada - The Canadian transcontinental train may have 33 train cars during peak season (May to September)
The length of passenger trains generally has to match the length of platforms, especially high-level platforms. These platforms cannot always be extended to suit extended train lengths due to bridges, tunnels, pointwork, narrowing track centers and stabling yards, though "selective door opening" can help long trains stop at short platforms.
Special test runs
(These are one-off to set records)
Bulk (ore, coal etc)
- BHP Run on 21 June 2001, comprising 682 wagons and hauled by eight 6000 hp General Electric AC6000CW diesel-electric locomotives controlled by a single driver with a total length of 7.353 km on the 275 km iron ore railway to Port Hedland in Western Australia – total weight 99,734 tons
- Sishen–Saldanha, South Africa. Run on 26–27 August 1989, comprising 660 wagons, 7.302 kilometres (4.537 mi) long and a total weight of 71 765 tons. The train comprised 16 locomotives (9 Class 9E 50 kV AC electric and 7 Class 37 diesel-electric).
- The longest and heaviest freight train ran on 20 February 1986 from Ekibastuz to the Urals, Soviet Union, was carried out with the coal train. The composition consisted of 439 wagons and several diesel locomotives distributed along the train with a mass of 43,400 tonnes and the total length of 6.5 kilometres (4.0 mi).
- Union Pacific, United States. Run from 8–10 January 2010, consisting of 296 container cars and hauled by nine diesel-electric locomotive spread through the train with a total length of 18,000 feet (3.4 mi; 5.5 km), from a terminal in Texas to Los Angeles. Around 618 double-stacked containers were carried at speeds up to 70 mph/112 km/h. 14,059 t.
- BNSF, United States, 2010—3.03 km 
- Kijfhoek–Breda, Netherlands. Run on 19 February 1989, as a test and publicity stunt what would become the longest passenger train in the world. The train was pulled by one 1500 V DC locomotive and had 60 passenger cars, of which only the first 14 cars held actual passengers during the run.
- Ghent–Oostende, Belgium. On 27 April 1991, one electric locomotive and 70 passenger cars (totalling 1733 m and 2786 ton, excluding locomotive) held a charity run for the Belgian Cancer Fund, thereby exceeding the Dutch record.
- Distributed power—Where operational considerations or economics require it, trains can be made longer if intermediate locomotives are inserted in the train and remotely controlled from the leading locomotive.
- Heaviest trains
- High-speed rail
- Track gauge
- Extreme Trains on the History Channel 2009
- List of steepest gradients on adhesion railways
- Longest train journeys (passenger)
- International Heavy Haul Association
- Longest road trains
- Popular Mechanics: http://www.popularmechanics.com/technology/engineering/extreme-machines/4345689
- "Leigh Creek Coal Now Major Asset.". The Advertiser (Adelaide, SA : 1931–1954) (Adelaide, SA: National Library of Australia). 7 October 1954. p. 3. Retrieved 3 October 2012.
- Light Railways October 2013, pg 22
- Railways Africa—MAURITANIA’S LONG TRAIN
- Railway Gazette International November 2010, p56
- Railway Gazette International May 2014, pg9
- Modern Railways Jan 2009, p71
- Railway Gazette International April 2011
- 835 m lange Güterzüge zwischen Padborg (DK) und Maschen geplant
- Modern Railways November 2012, p78]
- Långt tåg vid vattendrag (in Swedish with photo). It departs as two trains because of platform length but is combined shortly after.
- "Hamersley Freight Line—Railway Technology". Railway Technology. Retrieved 2011-10-17.
- Four world rain records shattered by the SA Transport Services (1989)
- Re: Longest freight train in the U.S.
- Kazakhstan railways
- "Safety, traffic concerns raised when 3.5-mile-long freight train rolls through L.A. Basin". LA Times. Retrieved 2011-10-17.
- Railway Gazette International March 2010, p7.
- De langste reizigerstrein ter wereld