Public transport systems offer many advantages over the personal alternatives when it comes to getting large numbers of people from A to B in style and safety - less congestion, less pollution and lower costs for starters. But while we certainly see plenty of impetus on the personal transport front here at Gizmag, fresh concepts for the future of mass transport don't seem to enjoy the same level of exposure, despite the fact that many cities around the world are still saddled with public transport infrastructure that's been in place for over a century. There are some radical plans in the works, however, and the 21st Century will undoubtedly bring with it a raft of people moving projects that redefine our notion of public transport. So just what will be pulling into the station in 50 years time? Read on for our pick of the most tantalizing concepts out there.

1. Superconducting vacuum trains

While fast, frictionless maglev train systems have been operational for decades, they haven't exactly become ubiquitous - perhaps because of the cost of the systems, or perhaps because there is no compelling need to replace the already widespread and workable conventional railway infrastructure. Either way, the idea is not about to fade from our collective imagination and several maglev of the future concepts have been floated.

The Evacuated Tube Transport (ETT) system envisions superconducting maglev trains operating in evacuated tubes at speeds of up to 6,500 km/h (4,039 mph) on international trips - that's New York to Beijing in two hours! The proponents of this system say that ET3 could be 50 times more efficient than electric cars or trains.

Terraspan goes even further than ultra-efficient mass transport with its vision for a network of superconducting tunnels. As well as providing infrastructure for "Terraspan trains," this network would also facilitate zero loss transmission of electricity to our homes.

A 500 km/h (310 mph) vacuum train project has also been proposed for Switzerland, but as the Swissmetro site outs it: "So a far-advanced technology of and for the next generation remains in the drawer."

2. String theory

Another high-speed rail concept that aims to present an alternative to conventional systems without the astronomical price tag is Anatoly Unitsky's String Transport System. The concept is based on the use of what look like heavy-duty above ground electrical wires, but instead of carrying power, these high-tension wires become the support for carriages.

The proponents of the system see big advantages in terms of cost (somewhere between three and 10 times less expensive than a railway, maglev system, monorail system or motorway) and efficiency (an 80 kW (107hp) motor would take a 20-person passenger vehicle up to 155 mph (250 km/h)).

3. Reversing roles

Taking the above ground rail concept further (and then turning it on its head) is Robert C. Pulliam's Tubular Rails. In this system the trains themselves carry the tracks, while the wheels and motors are contained in elevated rings that the train passes through at speeds of up to 240 km/h (150 mph). Because the design would cause minimal disruption to existing infrastructure and the technology is readily available, Tubular Rail estimates that construction costs could be 60 percent less than conventional urban train networks.

4. Sharing the street

This is definitely one of the most interesting public transportation concepts we've encountered over the years when it comes to reducing urban congestion, while making use of existing infrastructure. The "straddling bus" would roll on stilts above traffic using small tracks positioned between lanes of traffic while passengers get on and off at elevated bus stops. The result: additional people carrying capacity for urban roads, no disruption to traffic and no need to build completely independent track systems. Seems like a win/win, but at this stage we're not aware of any progress on the expected pilot program.

5. Human-powered mass transport

Another outside-the-box approach to transport that deserves a place in our top 10 is the Shweeb. This human powered monorail system uses bicycle pods suspended from tracks to create a very efficient option for getting from A to B.

Currently you can ride the Shweeb at the Agroventures in New Zealand where you can reach speeds of up to 45 km/h (28 mph) under your own steam. The idea is not limited to adventure parks though. Shweeb picked up a US$1 million investment from Google in 2010 as part of Project 10^100 and the company says it will soon be announcing the planned location of the first Shweeb built for public use.

6. High-speed, alternative energy

The quest for more efficient transport systems doesn't necessarily have to come at the cost of speed. The SolarBullet project is a campaign aiming to bring high-speed (we're talking 220 mph (354 km/h)) trains to Arizona using tracks equipped with solar panel carrying canopies that would provide the 110 megawatts of electricity that the system needs to run. The project is currently in the R&D phase but faces several hurdles (not the least of which is an estimated US$27 billion pricetag) before construction of the planned Tucson to Phoenix line can get underway.

While on the subject, solar isn't the only alternative energy being considered for powering train networks. The T-Box envisions turbines incorporated into tracks that could be used to harness wind energy from the train as it whooshes overhead.

7. Power from the road

While contactless systems that allow personal electric vehicles to recharge on the go are gathering momentum, these systems also hold potential for making mass transportation greener and more efficient. A real-world example of this technology has already been demonstrated in the form of a trackless "train" developed by researchers at the Korea Advanced Institute of Science and Technology (KAIST). The pilot project in Seoul’s Grand Park in Gwacheon City involved running an engine and three passenger cars using power supply infrastructure buried under the ground in sections of a 2.2 km (1.36 mile) long track.

So why not just charge the electric train at the socket? The advantage here is that the vehicle can operate with a battery that's one-fifth of the the size of batteries installed in electric vehicles currently on the market. While this means gains in efficiency, this needs to be weighed against the loss in efficiency caused by contactless charging, which in the KAIST experiment peaked at 74 percent. KAIST hopes to commercialize this technology within the next few years.

8. Ditching the driver

These days we think of road and rail transport as completely different things, but this distinction is set to become a little muddy as technology marches towards 2050. One of the benefits of public transport in general is that it avoids the inherent chaos of personal transport where the decisions are made by individual drivers. "Follow-the-leader" systems are looking to solve this problem by using a lead vehicle that's wirelessly linked to a series of other cars or "carriages" which follow its path autonomously. The system retains the flexibility of purely private transport (i.e. vehicles can leave the train so that you don't all have to end up at the same destination), the only additional infrastructure required is the computers that link the vehicles and the benefits for road safety, decreasing congestion and reducing vehicle fuel consumption are obvious.

This best of both world's idea sits in the "very near future" category - a European project dubbed SARTRE (Safe Road Trains for the Environment) project has been in progress since 2009 and was recently successfully demonstrated on public roads for the first time.

9. Orbital Maglev

Some future transport concepts have loftier goals that just getting us to the station on time. While space tourism based on more conventional rocket ships is a fast growing infant, there are also plans afoot to use "space trains" to launch passengers into orbit.

Like the EET discussed above, the Startram system would use a superconducting, magnetically levitating train capsule in a vacuum tube. The difference here is that the final 12 miles (20 km) of the 1,000 mile (1,609 km) long track would point upwards, launching the "carriage" into low earth orbit. If that's not futuristic enough, the plan sees the skywards pointing launch tube itself being held in place by magnetic levitation!

Conceived by Dr. George Maise along with one of the inventors of superconducting maglev, Dr. James Powell, the potential of this system to significantly reduce the costs of putting commercial cargo (and space tourists) into orbit is attracting serious discussion.

10. Space Elevator

Another long standing and noteworthy concept that aims to democratize the process of getting off the planet is the space elevator. First theorized over 100 years ago, the idea of the space elevator is to use a cable tethered to a base station to send "climbers" into orbit at a fraction of the cost of rocket-based launch systems.

While there are a variety of designs, the key component of a working space elevator would be a thin tether made from lightweight material (carbon nanotubes are the prime candidate) that stretches from an anchor point or base station on or near the Earth's equator to a point some 60,000 miles (96,560 km) into space. The Earth's rotation and a counterweight on the upper end of the cable would keep the line taught and climbers (likely powered by solar energy) traveling at fast train pace would be sent up this futuristic beanstalk to deliver cargo and people into orbit and back.

According to the International Space Elevator Consortium (ISEC), the cost of transporting cargo in this way "will be significantly reduced in price to the realm of dollars per kilogram compared with over $20,000 per kilogram today."

This is an idea that could well become reality before the curtains are drawn on the 21st Century - in fact, Tokyo-based construction company Obayashi Corp. has stated plans to have a 96,000 kilometer (59,652 mile) space elevator capable of carrying 30 passengers at a time operational by 2050.

Have we missed something? If you know of any mass transport concepts we've overlooked that have the potential to reinvent our urban and intercity journeys in the future, we'd love to hear your thoughts in the comments section.

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