An atmospheric railway uses air pressure to provide power for propulsion. In one plan a pneumatic tube is laid between the rails, with a piston running in it suspended from the train through a sealable slot in the top of the tube. Alternatively, the whole tunnel may be the pneumatic tube with the car being the piston with a seal to the walls. By means of stationary pumping engines along the route, air is exhausted from the tube leaving a partial vacuum in advance of the piston or car, and air is admitted to the tube behind the piston or car so that atmospheric pressure propels the train. In some plans, air pressure is applied behind the piston/car. A number of systems were built in the early to mid 19th century but none lasted long. New designs have been developed since the 1970s with one in operation on a few sites.
Historical applications 
In 1799 George Medhurst of London discussed the idea of moving goods pneumatically through cast iron pipes, and in 1812 he proposed, but never implemented, blowing passenger carriages through a tunnel.
In 1835 Henry Pinkus launched a prospectus for the National Pneumatic Railway Association. It was in 1838, when the gas engineer Samuel Clegg and the marine engineers Jacob and Joseph Samuda jointly took out a patent “for a new improvement in valves” that atmospheric propulsion became possible. The partnership set up a working model at the Samuda Brothers’ workshop in Southwark in 1839, and a 0.5-mile (0.8 km) demonstration track of the Birmingham, Bristol & Thames Junction Railway at Wormwood Scrubs between 1840 and 1843. In 1841 Joseph d'Aguilar Samuda published A Treatise on the Adaptation of Atmospheric Pressure to the Purposes of Locomotion on Railways. The Clegg-Samuda system attracted the attention and support of some of the foremost railway engineers of the day, notably William Cubitt, Charles Vignoles and Isambard Kingdom Brunel, each of whom was engaged on the construction of new railway lines. It was also severely criticised by other engineers and railway commentators, notably Robert Stephenson and John Herapath.
Dalkey Atmospheric Railway 
The first practical use of the system was on the Dublin and Kingstown Railway's Dalkey Atmospheric Railway between Kingstown (Dún Laoghaire) and Dalkey, Ireland, This 1.75-mile (2.82 km) line was built by Vignoles and operated between 1844 and 1854.
London and Croydon Railway 
Cubitt recommended the system for the 7.5-mile (12.1 km) London and Croydon Railway between London Bridge station and Croydon. Clegg and Samuda were invited by the directors to supply equipment to operate their trains between London Bridge and Epsom. The first stage of this project (between Croydon and Forest Hill) opened in January 1846, but many problems both with the pumping equipment and in maintaining air-tight seals in the delivery pipes were encountered. The London and Croydon Railway became a part of the London Brighton and South Coast Railway in July 1846 and the new board of directors invited Samuda to operate the new atmospheric railway on their behalf in return for a fixed fee. Once further propulsion problems became apparent in the second section of line to be equipped, between Forest Hill and New Cross, during 1847 the atmospheric method of propulsion was abandoned and the equipment sold.
One part of the pneumatic infrastructure was the viaduct from Sydenham to Crystal Palace, crossing the main lines. The pneumatic pipe could not cross the metals, so it was necessary to build a fly-over. This is reputed to be the first of its kind and is still in use today.
South Devon Railway 
The extension of Brunel's broad gauge railway westward from Exeter towards Plymouth by the South Devon Railway Company (SDR) involved one of his most interesting uses of technical innovation. Brunel and others from the GWR travelled to Ireland to view the atmospheric system at Dalkey first hand. Afterwards Brunel's engineer of locomotives for the GWR, Daniel Gooch, calculated that conventional locomotives could work the proposed Plymouth line at lower cost, but Brunel's concerns with the heavy grades led him to try the atmospheric system regardless.
The 20-mile (32 km) section from Exeter to Newton (now Newton Abbot) was completed on the principle, with stationary engines at around 3 mi (5 km) intervals. Trains ran at speeds of up to 70 miles per hour (113 km/h), but service speeds were usually around 40 mph (64 km/h). The level portions used 15-inch (38 cm) pipes and the steeper gradients west of Newton were to have used 22 in (56 cm) pipes. It is not clear how the change between the two pipe sizes would have been achieved unless the piston carriages were changed at Newton. It is also unclear how the level crossing at Turf was operated as the pipe projected above the rails.
The harsh environment of the line, which runs next to the sea and is soaked with salt spray in even moderate winds, presented difficulties in maintaining the leather flaps provided to seal the vacuum pipes, which had to be kept supple by being greased with tallow; even so, air leaked in, destroying the vacuum. Unfortunately, the tallow made the greased leather attractive to rats, whose depredations further reduced the efficiency of the seal.
Atmospheric-powered service lasted less than a year, from 1847 (experimental services began in September; operationally from 23 February 1848) to 9 September 1848. The accounts of the SDR for 1848 suggest that the atmospheric traction cost 3s 1d per mile (£0.10/km) compared to 1s 4d (£0.04/km) for conventional steam power. Part of the problem was that the engines had to be run for longer than expected, as they were not initially connected to the telegraph and so had to pump according to the railway timetable until the train passed, which increased pumping costs.
Despite the building of several engine houses, the system never expanded beyond Newton. The proposal to use the same system on the Cornwall Railway was not pursued.
There are remains of several South Devon Railway engine houses, including one at Starcross, on the estuary of the River Exe. It is a striking landmark and a reminder of the atmospheric railway, commemorated by the name of the village pub, the 'Atmospheric Railway'. A section of the pipe, without the leather covers, is preserved in Didcot Railway Centre and at the Newton Abbot Town and GWR Museum, in Newton Abbot, Devon.
Other early applications 
- The Paris–Saint-Germain railway between Bois de Vésinet and Saint-Germain-en-Laye, France (5.3 mi (8.5 km)) 1847–60 was totally replaced by a vapor system in 1861.
- The Crystal Palace atmospheric railway of 1864 had seals around the carriage, so (like Rammell's similar London Pneumatic Despatch Company) the whole carriage fits in a tube tunnel and was propelled by the large fixed fan.
Recent applications 
Aeromovel (in operation) 
The Aeromovel Corporation markets an automated people mover that is air driven. Lightweight trains ride on rails mounted on a elevated hollow concrete box girder that forms the air duct. Each car is attached to a square plate (within the duct) by a mast running through a longitudinal slit that is sealed with rubber flaps. Stationery electric blowers are located along the line to either blow air into the duct to create pressure or to exhaust air from the duct to create suction; as in other systems the pressure differential acting on the plate causes the vehicle to move. Electric power for lighting and braking is supplied to the train by a low voltage (50V) being applied to the track; this is used to charge onboard batteries. The trains have conventional brakes for accurate stopping at stations; these brakes are automatically applied if there is no pressure differential acting on the plate. Fully loaded vehicles have a ratio of payload to dead-weight of about 1:1 which is up to three times better than conventional alternatives. The vehicles are driverless with motion determined by lineside controls. Aeromovel was invented in the late 1970s by Brazillian Oskar Coester.
Constructed Aeromovel systems
- Porto Alegre, Brazil (downtown): a demonstration line with one-station (two platforms). First opened in 1983 and `completed' in 1987, the ~0.9 km (0.56 mi) line runs beside the Avenue Loureiro da Silva and Avenue President João Goulart in downtown Porto Alegre
- Taman Mini Indonesia Indah, Jakarta, Indonesia: opened in 1989 serving a theme park, a 2-mile (3.22 km) loop with six-station and three trains. (In use for over 24 years, it is now the longest operating atmospheric railway in history.)
- Porto Alegre, Brazil (airport): Construction is nearing completion of the first commercial line connecting the Estação Aeroporto (`Airport Station' on the Porto Alegre Metro) and Terminal 1 of Salgado Filho International Airport; the single-line will be 0.6-mile (1 km) long with a travel time of 90 seconds. Major engineering is complete and the first vehicle was delivered in April 2013 with the line is due to open in the second half of 2013.
Proposed Aeromovel systems
- Nova Iguaçu, Brazil: Planning has been completed for construction of a 4.5 km (2.8 mi), eight (8) station system. Reports indicate funding of R$252 million was allocated in 2012 by the central government with construction due to commence in 2013-14.
- Porto Alegre, Pontifical Catholic University of Rio Grande do Sul (PUCRS) & Universidade Federal do Rio Grande do Sul (UFRGS): Plans have been developed for a six-station, 2.27 km (1.41 mi) system connecting adjacent campuses the two universities. Financed primarily by the Brazilian Agency for Innovation (FINEP), approval was granted on 10-Feb-12 for the construction of a first phase which is a short section of track across a major road (Avenida Ipiranga). The whole project has a three year time frame and is meant to allow for further research into the technology. No reports exist of the commencement of construction..
Flight Rail (scale prototype) 
Flight Rail Corp. is developing a high-speed atmospheric train that uses vacuum/air pressure to move passenger modules along an elevated guideway. Stationary power systems create vacuum/pressure inside a continuous pneumatic tube (power tube) located centrally below rails within a truss assembly. As these power systems pull the air from the power tube, they create a vacuum in front of a free piston that is guided by rails inside the power tube. The free piston is magnetically coupled to the passenger modules above. Additionally, air enters the tube behind the free piston to create differential pressure. The magnetic coupling allows the interior of the power tube to be a closed system to maintain the desired pressure differential in the tube. The transportation unit operates above the power tube on a pair of parallel, steel rails that receive, support, and guide the wheels of the truck assemblies. The company currently has a 1/6 scale pilot model operating on an outdoor test guideway. The guideway is 1385 feet (422 m) long and incorporates 2%, 6%, and 10% grades. The pilot model operates at speeds up to 25 m.p.h. (40.25 km/h).
'Whoosh' (concept only) 
A web page describing a system called 'Whoosh' was available for a time. The system is a single monorail track of the vacuum tube with a track either side. The piston in the tube is connected to the carriage below which is supported by wheels running on the tracks each side of the tube.
Advantages & Disadvantages 
- Hillclimbing ability: As traction is not dependent on steel-on-steel adhesion and is somewhat independent of the track conditions (such as snow, ice or rain) the ruling gradient of such railways should exceed that of conventional modes. Of the two longest-lived 19th century applications, at Dalkey (max.:1 in 57, 1.75 %) and Saint-Germain (max.:1 in 33, 3.03%), this seems to have been vindicated: the system was used on uphill journeys and gravity in the other direction. The 20th century Aeromovel claims a maximum gradient of 1 in 8.33 (12%) which is steeper than any conventional railway in operation and equivalent to rubber-tyred metros.
- Infrastructure Savings: Atmospheric railways could be operated on cheaper, lighter tracks and cheaper bridges and viaducts which do not have to carry the weight of a locomotive (and its fuel if not electric). It could also take advantage of sharper curves further reducing costs of line construction.
- Fuel efficiency: It should be far cheaper to maintain and operate a few large pumping engines than a large number of individual locomotives. However in the South Devon Railway, as noted above, the operating cost was 2.5 times that of a conventional railway because the engine use could not be coordinated efficiently with demand. This does not affect the 20th systems that use electricity and can identify the position of vehicles on the line using sensors.
- Cleanliness: The smoke and dirt from the steam engines was kept away from the passengers.
- Safety: It is impossible to operate two trains on the same stretch of track in opposite directions simultaneously and so collisions would be avoided. If trains were running in the same direction then as the distance between them narrows a pressure buffer would automatically be created in the duct preventing a collision; the pressure becomes greater the closer the vehicles come to one another. Also as the pressure plate is enveloped by the duct the vehicle is effectively held to the track, making derailing almost impossible.
- Maintenance: Because all the components of the system use relatively simple technology, the engines are not subject to vibration and the axle loads are low, both the amount and frequency of track, vehicle and engine maintenance and the need for specialized labor to carry it out is theoretically less than comparable systems. This applies particularly to the more modern systems using standard industrial electric blowers.
The failure of the 19th century systems was due to technical problems with the stationary engines and the leather seals on the vacuum pipes. The former were suffered by the London and Croydon Railway but would have been overcome with more experience by the manufacturers and operators. The difficulty of maintaining an air-tight seal in the vacuum pipes was a serious problem, particularly for the South Devon Railway Company, which was never satisfactorily solved using the materials and technology of the 1840s.
The atmospheric system also suffered from a number of operating problems.
- Shunting the trains into atmospheric formation was difficult or cumbersome (although this would have seemed less of a problem in an era when much shunting was carried out by horse- or man-power).
- A change in traction, with consequent delays, would be necessary if an atmospheric line became part of a through route.
- There had to be gaps in the atmospheric tubes at points, with flyovers or similar arrangements at junctions; and special arrangements would have been needed at level crossings.
Overall assessment 
The atmospheric system foresaw the inherent efficiencies of delivering centrally generated power to the line side rather than generating it on individual locomotives, as would ultimately become the normal practice with electrification systems. The use of modern materials and technology would overcome many of the problems of the original systems, but atmospheric railways were ultimately too inflexible for widespread use.
The durability of the Jakarta installation and the construction of the first commercial point-to-point people mover in 2013 indicates that there may be a niche where the advantages of the system makes it a preferred option to other solutions.
See also 
- Dalkey Atmospheric Railway
- Beach Pneumatic Transit in New York City, United States (1869)
- Crystal Palace pneumatic railway
- Cable railway – a more successful albeit slow way of overcoming steep grades.
- Funicular – a system of overcoming steep grades using the force of gravity on downbound cars to raise upbound cars
- Steam catapult – the arrangement of seal and traveller is essentially the same, albeit all steel.
- Vactrain – combination of gravity and air power
- "Jolly-sailor Station". The Pictorial Times. 1845
- R. A. Buchanan, ‘The Atmospheric Railway of I.K. Brunel’, Social Studies of Science, Vol. 22, No. 2, Symposium on 'Failed Innovations' (May 1992), pp. 231–2.
- Samuda, J. D'A (1841). A Treatise on the Adaptation of Atmospheric Pressure to the Purposes of Locomotion on Railways. London: John Weale, 59 High Holburn.
- "Dalkey Atmospheric Railway". Archived from the original on 30 December 2005. Retrieved 19 July 2007.
- *Howard Turner, Charles (1977). The London Brighton and South Coast Railway. 1 Origins and Formation (1st edn ed.). London: Batsford. ISBN 978-0-7134-0275-9. 239–256.
- Awdry, Christopher (1992). Brunel's Broad Gauge Railway. Sparkford: Oxford Publishing Company. ISBN 978-0-86093-504-9.
- Kay, Peter (1991). Exeter – Newton Abbot: A Railway History. Sheffield: Platform 5 Publishing. ISBN 978-1-872524-42-9.
- The atmospheric railway. Accessed: 4 February 2012.
- The Atmospheric Railway Exeter Memories. Accessed: 4 February 2012.
- Brunel's Atmospheric Railway Devon Heritage. Accessed: 4 February 2012.
- New York Times, 10 Nov 1852
- Chemins de fer atmosphériques
- "Pneumatic propulsion system for freight and/or passenger vehicles". US Patent 4658732.
- "Aeromovel - Techonology". Retrieved 30 April 2013.
- "website with comparison table of payload to dead weight of people movers".
- "US Patent 5,845,582 Slot sealing system for a pneumatic transportation system guideway". United States Patent 5845582. Retrieved 30 April 2013.
- "THE AEROMOVEL HAS ALREADY BEEN OPERATING FOR 24 YEARS IN INDONESIA USING BRAZILIAN TECHNOLOGY". Retrieved 30 April 2013.
- "Atmospheric and Pneumatic Railways".
- "Aeromovel downtown test track on OpenStreeMap".
- The Porto Alegre City Council discussed in May-13 pulling down the test line to create better access to park land. http://zerohora.clicrbs.com.br/rs/geral/noticia/2013/05/prefeitura-de-porto-alegre-cogita-derrubar-antiga-linha-do-aeromovel-para-criar-parque-4125874.html
- http://tamanmini.com/sarana-keliling/shs-23-aeromovel-indonesia-2?lang=en SHS-23 Aeromovel Indonesia
- "Lee H. Rogers Obituary (Lee Rogers was intrumental in the Taman Mini Aeromovel project)".
- "WITH 100% OF NATIONAL TECHNOLOGY, THE AEROMOVEL REACHES ITS FINAL CONSTRUCTION STAGES IN PORTO ALEGRE". Retrieved 22 April 2013.
- http://www.pucrs.br/research/research_in_focus.htm Research at PURCS
- "The Project Aeromovel". Retrieved 8 May 2013.
- The Whoosh: Innovative Public Transport Archived June 25, 2007 at the Wayback Machine
- Maglev railways and those using linear motors share this traction advantages of atmospheric railways over conventional railways. Inclement weather however can affect the effectiveness and durability of the pressure seal.
- "Charles Blacker Vignoles: Romantic Engineer" by By K. H. Vignoles, p.97
- Journal of the Franklin Institute, Volume 32; Volume 62, 1856 p.14
- Howard Turner, J.T. (1978). The London Brighton and South Coast Railway, Vol.2 Establishment and Growth=Batsford. London, England. ISBN 978-0-7134-1198-0. p.5-8.
Further reading 
- Clayton, Howard (1966). The Atmospheric Railways. Lichfield: Howard Clayton.
- Hadfield, Charles (1967). Atmospheric Railways (1st edn ed.). Newton Abbot: David & Charles. ISBN 978-0-7153-4107-0.
- US4658732 (Aeromovel) Pneumatic propulsion system for freight and/or passenger vehicles
- US5845822 (Aeromovel) Slot sealing system for a pneumatic transportation system guideway
- Brunel portal