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For the use of "unimodal" in mathematics and statistics, see Unimodal function

UniModal or SkyTran is a proposal by Douglas Malewicki for a 160km/h (100mph) personal rapid transit system using electric linear propulsion and a form of passive magnetic levitation called Inductrack.

The UniModal design is significantly different from other PRT systems. Vehicles are suspended from an overhead track and are aerodynamically streamlined. Also, the system uses passive magnetic levitation and is proposed to use speech recognition to interact with riders.

The system is designed to have very few moving parts (for economic reasons), the main moving part being the vehicle itself. The promoters refer to the system as "solid state". However, wheels are present for use during starting and stopping, and the doors move, as well as any moving conveniences such as fans to air from heaters or air conditioning units.

Guideway

Guideways would be mounted on poles about 30 feet above the ground. The guideways would be made of modular steel components, attached to a cemented foundations. In the past, the company has estimated a possible $1 million per mile once in mass production.

Pods

Projected estimates:

• Running cost: $0.01 per mile (~ 200 mi/gallon)

Because SkyTran operates at higher speeds than other PRT designs, the pods are designed to be aerodynamically streamlined. Vehicals with lower air drag use less energy and produce less noise. The pod is designed to carry two people in tandem (one behind the other) for decreased air drag. The company plans to charge 10 cents per mile, about the cost of gas in a car.

The doors do not have handles (inside or out), but open automatically. However, there is a door release mechanism on the outside of the pod to allow rescuers to open the door.

Resting pods sit on small wheels, but when the pods are accelerated to above around 2 mph, the pods are levitated by the Inductrack in the guideway. After slowing to below 2 mph, the wheels act as landing gear to support the pod.

System Description

Hypothetical Trip

A person would approach a portal, walk up the stairs, and get in the ready pod. One would tell (verbally) the pod where they want to go, and the pod door would close automatically. The pod would then accelerate forward and up along the acceleration guideway, and would then merge with the main guideway at 100 mph. The pod would travel to the destination portal and would exit on the decelerate track, then start slowing down, and presently stop at an exit portal. The door would automatically open, and the person would get out and walk down the stairs. The pod would then close its door, and edge forward to wait in a line with other pods, all waiting for people to use the pod in front at the entrance portal.

Ideal Guideway Grid

The guideway is designed to accommodate a 3D grid design. It is called 3D because the guideway can be built under or over other things - especially other guideways. The main reason to have such a grid is to avoid intersections - guideways can cross over or under other parts of the guideway so that no stops are necessary - much like freeway overpasses allow the cars on the freeway to continue non-stop.

Although the design suggests a guideway grid, the UniModal design permits guideways to be used in any configuration - such as a linear route system (like most train routes).

Decelerate - tracks, and brakes

Like all PRT systems, vehicles exit the main guideway, then slow and then stop on a deceleration guideway. This is analogous to the way cars exit a freeway, rather than remaining on the road). In this way, the main guideway can allow a constant speed. The design proposes that vehicles slow down to 20 mph on the deceleration guideway before actually making any turn.

The UniModal design proposes using regenerative brakes for normal braking, but in an emergency, an emergency brake pad would press against the inside of the steel rail, permitting fast emergency deceleration. The designers propose a 6 G maximum emergency braking deceleration. The pods would have seatbelts resembling race car seatbelts - with a wider belt and an X shaped harness - to be safer in emergencies.

This deceleration rate was chosen in order to enable vehicles at 1-second headways to comply with rail safety standards requiring that a public transportation vehicle to be far enough behind the vehicle in front of it to make a complete stop in a very short distance. Note that rail safety standards do not yet apply to PRT systems, and that this braking rate is considered unsafe for the general population by most authorities.

Concerns about the disabled

SkyTran proposes that, instead of designing the system so disabled people can use it, it would be cheaper to gives these people door to door taxi service instead.

Inductrack

The magnetic levitation system would be the passive "Inductrack" system using Halbach arrays, as developed by physicist Richard Post at Lawrence Livermore Laboratories. Passive maglev requires no power to levitate vehicles.

Magnetic levitation permits low "friction" (present as magnetic drag). Lawrence Livermore National Laboratory reports that at 100 mph, a 700 pound vehicle would require 408 watts (equivalent to .54 horsepower) to overcome the magnetic drag. By comparison, conventional cars (varying greatly around 3000 pounds) traveling at 65 mph consume between 3000 and 8000 watts.

Intercity vs intracity travel

• Intracity travel is travel within a city. Pods would travel at 100 mph on these lines.
• Intercity travel is travel between cities. Pods would travel at 150 mph on these lines.

Due to air resistance, the energy costs of a vehicle increase as the cube of its speed (approximately). Therefore the intercity plan (at 150 mph) has energy costs 3.4 times as much per mile as the intracity plan (100 mph).

External links

• http://www.unimodal.com
• http://www.skytran.net

See also

Personal Rapid Transit is the generic term for a family of similar systems.

• Vehicles
• Transportation