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SkyTran is a Personal Rapid Transit system first proposed by inventor Douglas Malewicki in 1990, and under development by Unimodal Inc. Lightweight two-passenger vehicles suspended from elevated passive magnetic levitation tracks are expected to achieve the equivalent of over 200 miles per US gallon (240 mpg-imp; 1.2 L/100 km) fuel economy at 100 miles per hour (160 km/h) or faster. A prototype of the SkyTran vehicle and a section of track have been constructed. Inductrack, the proposed magnetic levitation system for SkyTran, has been tested by General Atomics with a full-scale model. UniModal Inc. is now collaborating with NASA to test and develop SkyTran. A SkyTran system is being built in Israel as a pilot project. It is due to be completed in Tel Aviv by the end of 2015. Additional projects have been proposed and/or are planned in France, Germany, India, Indonesia, Malaysia, Pakistan, Saudi Arabia, Slovenia, the United Kingdom, and the United States.
To minimize maintenance and make switching on and off the tracks efficient at high speeds, early versions of the system proposed using the Inductrack passive magnetic levitation system instead of wheels. Passive maglev requires no external power to levitate vehicles. Rather, the magnetic repulsion is produced by the movement of the vehicle over shorted wire coils in the track. The cars would be driven by a Linear motor in the track or vehicle. Therefore, the system will have very few moving parts; primarily just the vehicle itself moving along the track, its parking wheels and door, and fans in heating and air conditioning units; so its promoters refer to the system as "solid state".
The passive maglev coils are enclosed and supported by a light shell called a guideway that also captures the vehicles mechanically to prevent derailment. Malewicki proposes a 3D grid design that avoids accident-prone intersections by grade separation, with guideways and their exit and entry ramps crossing above or below each other. Tracks will be supported 20 or 30 feet (6 or 9 m) above the ground by standard metal utility poles. They could also be attached to the sides of buildings.
After identifying problems with Inductrack and the cost associated with it, SkyTran described an improved design during a Horizon BBC interview with SkyTran at NASA Ames in Mountain View, CA.
Comparison with other public transit systems
According to the US National Transit Database (record of every public transit system in the US), the average light rail system costs $5.66 per passenger ($1.78 for capital cost and $3.55 for operating cost). Light rail projects have cost $100 million per mile ($62,000,000/km) while SkyTran would cost only $10 million per mile ($6,200,000/km). Skytran infrastructure reduces the weight of empty vehicles to under 70 lb/ft (104 kg/m), compared with light rail vehicles weighing 990 lb/ft (1,473 kg/m).
Maximum capacity of the system is 11,500 passengers per hour per direction is reached by spacing vehicles at 1/2 second spacing. At 80 miles per hour (130 km/h), vehicles would be spaced at 59 feet (18 m) and stopped by multiple redundant safety systems. By automating control of the system, SkyTran would be made safer than driving by eliminating human error (> 95% cause of human traffic fatalities). As lines reach capacity, a new line would be built parallel to the first 0.5 to one mile away to provide better coverage of the network.
Malewicki conceived the basic idea of SkyTran idea in 1990, filing a US patent application that year that was granted as US Patent #5108052 in 1992. He published several technical papers on SkyTran in the following years. In 1991, he presented a paper entitled "People Pods - Miniature Magnetic Levitation Vehicles for Personal Non-Stop Transportation" to the Society of Automotive Engineers (SAE) Future Transportation Conference in Portland, Oregon.  The paper is a thorough description of the concept at that point, although some important features of the current SkyTran design are only discussed as options, including magnetic levitation rather than wheels and hanging below the guideway instead of riding above it.
The paper describes how Malewicki had built and driven a freeway-legal 154-MPG car in 1981, but realized it could never be safe on a street surrounded by far larger and heavier vehicles. Elevated tracks would allow a very light vehicle to be safe. They are also basic to the system's inexpensiveness, because there is no need to acquire a huge right of way and tear down buildings. It presents an aerodynamic analysis (Malewicki is an aerospace engineer) supporting claims of very high energy efficiency (the paper claims 407 mpg-US or 489 mpg-imp or 0.578 L/100 km for SkyTran's current two-passenger tandem design, though the Unimodal site claims only, "over 200 mpg-US or 240 mpg-imp or 1.2 L/100 km"). It also described how a very light vehicle that can squeeze both surfaces of a track simultaneously could reliably achieve a 6-G deceleration, allowing it to brake safely to a stop from 100 miles per hour (161 km/h) in just 55 feet (16.76 m).
In 1999, Malewicki was invited to present an overview of the future of transportation for the Institute of Electrical and Electronic Engineers (IEEE) Proceedings. His submission, rather than projecting the future, described "a retrospective of solid-state transportation systems" imagining the progress of the SkyTran invention from the perspective of the year 2052.  A decade later, he was invited to present an update for their November, 2009 issue on linear motor-powered transportation.  In the same year, he also gave interviews to the industry magazines Industrial Design and EV World.
Once Malewicki and his partners began making proposals to transit systems, these proposals and their other efforts to publicize the idea began to be described in popular technology magazines and local and national news articles.
The 2008 energy shortages stimulated renewed interest in Green vehicle proposals such as SkyTran. The cover of Popular Science Magazine's June, 2008 special issue on "The Future of the Environment" featured a SkyTran-like vehicle prominently in its future "Green Mega-City". The "Maglev SkyTran" topic quoted a number of SkyTran and Personal Rapid Transit ideas, such as passengers exiting and boarding at off-line elevated "portal" stops while high-speed traffic continues to speed by on its main line.
In September 2009, the US NASA (National Aeronautics and Space Administration) signed a Space Act joint development agreement with Unimodal. Unimodal has tested prototype vehicles on short guideway sections at NASA's Ames Research Center, in Mountain View, California. NASA control and vehicle dynamics simulation software was made available to Unimodal, which hired NASA subcontractors to program them using US DOT grant funding. 
In June 2014, Unimodal and Israel Aerospace Industries (IAI) contracted to build a 400-500 meter elevated loop test track on IAI's campus in central Israel. If the pilot project is successful, IAI will build a commercial SkyTran network in the city of Tel Aviv.  
- Green vehicle
- Maglev train proposals
- MISTER A Polish PRT system with a similar design, but without the magnetic elevation or streamlined railway.
- Personal rapid transit
- Shweeb A human powered PRT project developed and tested as an amusement park attraction, and chosen for funding by Google based on submissions to its 10^100 idea competition.
- Sustainable transport
- "Maglev: A New Approach," Scientific American, January 2000.
- Lawrence Livermore national Laboratory
- http://www.nasa.gov/topics/nasalife/features/unimodal.html, retrieved November 1, 2010
- "Israel Is Building a Futuristic Transit System of Magnetic Pods". 26 June 2014. Retrieved 8 January 2015.
- RABINOVITCH, ARI (24 June 2014). "Futuristic elevated transport system to be built in Israel". Reuters. Retrieved 8 January 2015.
- Solid state
- US National Transit Database
- DeBolt, Daniel (April 1, 2010). "Could investors fund city's transit future?". Mountain View Voice.
- Siemens S70 rail car
- 2010 TRB paper vol. 2146
- Burke, Wallace R. (September 1, 1992). "Monorail vehicle". US Patent and Trademark Office. Retrieved June 21, 2015.
- "People Pods - Miniature Magnetic Levitation Vehicles for Personal Non-Stop Transportation" by Douglas J. Malewicki , AeroVisions, Inc, Irvine California, USA and Frank J. Baker, Monitoring Automation Systems, Irvine, California, USA June 1991
- People Pods, Table 2 "Performance Comparisons of Possible People Pod Concepts" on page 5
- "Benefits -- Energy Efficient"
- People Pods, Figure 7, "People Pod High 'g' Braking Capability" on page 8
- March 31, 2052: a retrospective of solid-state transportation systems. Malewicki, D.J. Proceedings of the IEEE Volume 87, Issue 4, Apr 1999 Page(s):680 - 687 Digital Object Identifier 10.1109/5.752524 Summary:The author discusses SkyTran, the personalized solid-state transportation (SST) system for the public. The author imagines that it is the year 2052 and he is looking back on the 50+ years which have seen a revolution in personal transportation. SkyTran is based on a MagLev monorail system with individual lightweight carriages traveling nonstop at 100 m.p.h. to the traveler's required destination. In this context the author considers; low-cost stations for efficient passenger handling; enhanced safety; cashless transactions; congested downtown station placement; vehicle mass production costs; fail-safe operations; and SkyTran on the Moon's surface.
- Malewicki, Douglas (November 2009). "Silicon is About to Change the World -- Again" (PDF). Proceedings of the IEEE 97 (11): 1750–1753. doi:10.1109/jproc.2009.2030226. Retrieved 1 March 2014.
- I. D. The International Design MagazineNovember 1999 "Future Transport" by David Pescovitz. Includes interview with Professor Jerry Schneider.
- "Interview with SkyTran Inventor and President Doug Malewicki (part 1)" by Bill Moore (Editor in Chief) EV World August 29, 1999. www.EVworld.com.
- "Interview with SkyTran Inventor and President Doug Malewicki (part 2)" by Bill Moore (Editor in Chief) EV World September 5, 1999. www.EVworld.com
- "Track to the Future" Reporter: Scott R. Gourley. Popular Mechanics May 1998.
- "SkyTran beats light rail, buses in cost, efficiency." Jerry Spellman, Mesa, AZ. Arizona Republic July 16, 1999
- "How do we go from here?" Jerry Spellman, Mesa, AZ. Arizona Tribune June 3, 1999.
- Tech 2010: #06 "The Morning Glide; The Train You're Never Late For", By PETER RICHMOND. _The New York Times Magazine_ Published: June 11, 2000.
- "The Green MEGA CITY: An eco-savvy blueprint for tomorrow's megacity that points the way to fresh air, clean water and traffic that never jams -- Transportation -- Maglev SkyTran". Popular Science Magazine. June 13, 2008. Archived from the original on June 17, 2008. Retrieved June 20, 2015.
- Marlaire, Ruth (September 2, 2009). "NASA Partners to Revolutionize Personal Transportation". Ames Research Center, Moffett Field, Calif. Retrieved June 21, 2015.
- Rabinovitch, Ari (June 24, 2014). "Israel's largest defense company to build world's first elevated transit network in Israel". Haaretz. Retrieved July 19, 2014.
- Winer, Stuart (June 24, 2014). "Futuristic skytrain track to be built near Tel Aviv". The Times of Israel. Retrieved July 19, 2014.
- SkyTran official site
- US Patent D329028, "Monorail vehicle", filed June 12, 1990 and issued September 1, 1992.
- Archive of old SkyTran.net site
- Are Magnetically Levitating 'Sky Pods' the Future of Travel?
- The International Maglevboard
- Skytran vehicle and guideway at NASA Ames
- NASA Skytran press release