Archive for the ‘General’ Category

Third Personal Rapid Transit Test Track Commences Operation

Sunday, January 29th, 2012

Modutram recently opened the station portion of their new full-scale test track in Guadalajara, Mexico thus becoming the third PRT supplier to have an operating test track. The system is currently running with one vehicle and successfully demonstrates switching capabilities.

Station and associated test track

Station and associated test track

The Modutram program is funded by the Mexican Government and is undertaken with university cooperation. The intent is to develop and commercialize a PRT system ideally suited to Mexican applications but capable of also being deployed elsewhere. The focus is on costs and $6M per one-way track-mile is the approximate cost target.

Vehicle approaching station

Vehicle approaching station

A variety of vehicles is being planned with the initial vehicle being designed for slow, short trips with standees. A hybrid vehicle is used in order to reduce the number of expensive batteries required. Electric motor and internal combustion engine options can function completely independently of each other. Vehicles have four-wheel steering and closely follow guideway sidewalls which are constructed to a 2mm lateral tolerance. Sidewall following is accomplished by two guide wheels mounted just ahead of and behind each road wheel. Physical following was selected over remote sensing in order to reduce development time. Remote sensing could be added at a later date.

Hybrid vehicle

Hybrid vehicle

A unique operational feature is that the vehicles will keep moving slowly through stations without completely stopping. This operation has proved successful when tested with handicapped passengers. Passengers alight as soon as the vehicle enters the station while others board just before it leaves the station. If no one boards, or if boarding is incomplete, the vehicle will stop in the station. Stations are arranged so as to keep boarding and alighting passengers separate (even to the point of having separate staircases).

System characteristics

System characteristics

 

Elevated track. Note superelevation.

Elevated track. Note superelevation.

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Personal Rapid Transit and Testosterone

Monday, July 18th, 2011

I have recently spent quite a bit of time meeting with and/or discussing PRT with different early-stage suppliers. The common theme seems to be that there is just too much testosterone in this business! Almost every vendor strongly believes that their solution is by far the best and that all others have fatal or near-fatal flaws. Gentlemen (there are no ladies in this group), it is in your own best interests to be a bit more humble and to not discount your competitors, they are generally smarter than you give them credit for.

Oftentimes when a competitor’s weaknesses are pointed out to me, I am aware that they are working on improvements and/or that these same weaknesses are not as serious as made out and/or are in fact strengths in some situations. I hope that all vendors are aware that marketing one’s strengths is more effective than marketing the competition’s weaknesses.

Those vendors who are in the very early stages should note that it has been many years since I have heard any representative of the three  vendors with commercially-available systems make a derogatory statement about any other! In fact these three vendors cooperate well in their efforts related to the Advanced Transit Association.

The table below attempts to summarize the stage of development that the significant vendors are in. I have no intention of mis-characterizing anyone’s efforts. If I have omitted or incorrectly categorized a company or two, please let me know. An open guideway system is one where the vehicles steer themselves (as opposed to a captive bogey system where the guideway steers the vehicles). Engineering design means more than pretty illustrations on a website. By Test Track I mean an active full-scale track demonstrating switching. A commerical project is one for which the vendor is being paid and is under contract (I realize I am giving ULTra-Fairwood the benefit of the doubt on Amritsar).

PRT Technology Development

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Personal Rapid Transit Reliability

Thursday, April 7th, 2011

Personal rapid transit (PRT) was originally envisioned as a new mode of urban transit. As such, extreme reliability was not required. It is appropriate to examine PRT’s reliability potential a little more closely now that it is being implemented in airports and under consideration for applications where reliability is very important, if not vital.

Reliability can be defined as the percentage of trips that meet predefined parameters. In a PRT system these parameters could be, for example, 50% of people wait less than one minute and 95% wait less than three minutes. Based on parameters such as these, the 2getthere Masdar PRT system is operating at 99.3% and the ULTra Heathrow PRT system achieved 99.6% during passenger trials. By contrast, the Morgantown PRT system achieves about 98.5%. All of these are considerably higher than transit level of service A which is defined as 97.5%.

Let’s examine what these percentages really mean. 97.5% reliability means that 25 trips out of one thousand (one in 40) do not meet requirements. So, if you have forty work trips a month on a bus system operating at level of service A, you can expect to be late for work, or late home, once a month.

98.5% means 15 trips per thousand do not meet requirements. This is 1.6 times (25/15) more reliable than 97.5%. Similarly 99.6% is 6.25 times (25/4) more reliable than transit level of service A.

PRT system developers can predict reliability by knowing the mean time between failures for critical components. It is good to see that both ULTra and 2getthere are achieving public service reliability values similar to those commonly seen on airport people movers. This implies that their statistical analyses of reliability issues were accurate.

While it is acceptable on most systems for a small percentage of passengers to receive slightly lower than desirable service every day, the question arises as to how often the system will fail completely and how is such failure defined. Let’s define complete failure as the entire system breaking down for 15 minutes and then immediately resuming full service. If the system we are considering has 0.0% reliability of serving essentially all passengers in 0 minutes and 99.5% reliability of serving essentially all passengers in 3 minutes, it is clear that the reliability at 15 minutes will be extremely high. This means that the chances of such a breakdown from known causes of failure will be extremely remote.

Extensive breakdowns are typically caused by unknown causes of failure which, by definition, cannot be statistically estimated. These failures are of two basic types – those that also impact most surrounding systems and those that only impact the system of concern. The latter type is the one that must be protected against. Fortunately it should be extremely rare. Nonetheless, if the PRT system is vital to facility operations, breakdowns must be mitigated.

PRT system breakdown mitigation usually takes the form of avoiding single points of failure and providing multiple backups or redundancies. Examples include alternative guideways or routings that can route passengers around a temporary guideway issue, backup power sources, redundant computer systems, emergency walkways and backup bus systems. Rather than fail completely, a good PRT system should have the ability to provide degraded, but acceptable, service at all times except when the failure is an event that is so significant as to shut down all other transportation systems in the area.

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Personal Rapid Transit Capacity

Sunday, January 9th, 2011

The burgeoning interest in personal rapid transit (PRT) in India is highlighting the issue of PRT capacity. This is a fairly complex topic that will be dealt with fairly briefly here. Note: network capacity is much more complex than just the guideway capacity that is dealt with here. PRT capacity is complex because it is impacted by a number of issues:

Brick wall stopping (BWS) criteria. This is a railroad safety criterion that many believe not to be applicable to PRT. Basically BWS requires that a train must be able to stop before hitting a preceding train if that preceding train instantaneously turns into a stationary brick wall. In order to meet BWS the time between trains (or T-Pods in the case of PRT) must be adjusted based on speed and the maximum available, or allowable, deceleration.

Deceleration. The maximum deceleration is a function of the available friction and of whether passengers are standing or sitting, wearing seat belts, etc. The available friction or deceleration force varies with the type of PRT system. PRT systems driven and decelerated by linear induction motors rely on their motors for their primary breaking force and are typically independent of friction and thus weather. The maximum breaking deceleration they apply is typically less than what is available. Rubber-tired PRT systems, on the other hand, are dependent on the friction between their tires and the riding surface which can be dramatically impacted by weather. These systems will usually have weather mitigation plans aimed at maintaining friction above about 0.25G where G is the force of gravity.

Minimum headway. This is the minimum time between vehicles measured from the front of one vehicle to the front of the other. For BWS criteria, it varies from about 1.4 seconds with 0.50G deceleration force at 15 mph to about 3.2 seconds with 0.25G deceleration force at 30 mph. Without BWS criteria many suppliers claim they will achieve minimum headways of 0.5 seconds. Cabintaxi demonstrated 0.5 second PRT headways but never proved endurance or safety at these headways. We therefore believe it prudent to plan for minimum headways of no less than 1.0 seconds. Headway is strongly tied to capacity since reducing headway by half theoretically doubles capacity.

Occupancy. This is the number of passengers per T-pod. Occupancy is also strongly tied to capacity since doubling the occupancy theoretically doubles capacity. However increasing PRT occupancy during peak hours usually involves ride sharing. This can be easily accomplished on small systems with few stations but is difficult to accomplish on large systems with many stations. Imagine how long a passenger bound to station 57 in a 100 station system would have to wait for another to arrive also bound for station 57. Ride sharing protocols to overcome this problem will be the subject of a future article.

The table below provides the theoretical guideway capacity in passengers per hour based on variations in the parameters discussed above. The reasonable capacity of PRT guideways is seen to range between about 1,000 and 14,000 passengers per hour. Since PRT systems tend to cost much less than other fixed guideway systems, it is usually useful to compare the costs required to meet the capacity demand.

Capacity2

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Masdar Personal Rapid Transit (PRT) Opens

Thursday, December 9th, 2010

On Sunday, November 28th, the Masdar PRT system opened to the public. To quote Larry Fabian, 2getthere, the manufacturer, got there. 2getthere operates the system with the support of Singapore Mass Rapid Transit. Masdar City is a new carbon-free city being developed adjacent to Abu Dhabi in the UAE.

The system has 10 passenger and 3 freight vehicles serving 2 passenger and 3 freight stations connected by approximately one mile of track. The system is in operation 18 hours a day, seven days a week serving the Masdar Institute of Technology. Trips take about 2 and a half minutes and are presently free of charge. Average wait times are expected to be about 30 seconds.

Masdar PRT Station

Masdar PRT Station

Robbert Lohmann, Marketing Director for 2getthere, is quick to point out that the elaborate stations are not necessarily reflective of what a station should look like, but more an indication of what one could look like, if desired.

As mentioned previously, it is unlikely that this system will be extended throughout the entire Masdar City as originally planned. However, it is hoped it will be expanded beyond the extent of the present rather limited system.

The Heathrow ULTra PRT system recently achieved 99.6% availability during four weeks of passenger trials. We look forward to receiving availability results from Masdar. It will bode well for PRT if they are in a similar range. To put 99.6% in perspective, it means 4 trips in a thousand do not go as planned. This is six times more reliable than transit level of service A for transit reliability as defined in TRB’s Transit Cooperative Research Program (TCRP) Report 100: Transit Capacity and Quality of Service Manual, where 25 trips per thousand are permitted to be late.

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Urban Personal Rapid Transit Guideways

Thursday, November 25th, 2010

Communities considering retrofitting personal rapid transit (PRT) guideways in urban settings are finding this is not always easily accomplished. In most situations it is logical for the guideways to be within existing street rights-of-way (ROW) and these are often cluttered/adorned with trees, overhead utility lines, street lights, traffic signals, signs, etc. In addition, the adjoining buildings often have little or no setback and can be significantly impacted by an elevated guideway in close proximity. To help highlight some of the opportunities and hurdles, we have developed a series of illustrations showing different potential guideway locations within an existing urban ROW. They conclude with some ideas for proposed (new) ROWs, highlighting the potential to reduce guideway visual intrusion, while taking advantage of the mobility offered by PRT to also reduce vehicle intrusion. The illustrations can be downloaded here.

The final two sketches are dramatically different than the others and prompt the question: “Shouldn’t this be the ultimate goal of PRT?” Visit this website to learn more about sustainable green cities enabled by PRT.

PRT proponents often promote the concept of using the guideway infrastructure to support streetlights and eliminate the need for overhead utilities. This very logical concept may prove quite difficult to implement in practice. Utility companies presently resist hanging their utilities on each other’s poles – a seemingly equally logical concept.

If common use of the guideway structure is to be accomplished, it will be important that each entity using the structure can obtain unhindered access to their key elements, without hindering the functioning of the key elements of the other entities. Utility lines strung on the guideway structure above a suspended PRT system (such as Beamways, MISTER or SkyTran) may be almost inaccessible, without somehow reaching over the dynamic envelope reserved for moving T-Pods – a maneuver unlikely to pass the safety certification process.

Utilities strung under the guideway of a supported PRT system with the bogie captured within the guideway structure (such as Skyweb Express) might pose similar problems if the guideway covers had to be removed while working in close proximity to the energized utility lines. The best opportunity for PRT and utilities to coexist seems to lie with supported systems of the open guideway type (such as 2getthere, ULTra or Vectus). Such systems could allow almost all PRT maintenance to be accomplished by workers working above the guideway riding surface and almost all utility maintenance to be accomplished by workers working below the guideway riding surface. Thus the riding surface would form a well-defined natural boundary between the systems.

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Why Has Masdar Personal Rapid Transit (PRT) Been Scaled Back?

Saturday, October 16th, 2010

Masdar City, near Abu Dhabi in the UAE, set out to be a sustainable, zero-carbon, zero-waste community. Part of the premise was to exclude automobiles entirely. The city was going to rely mostly on a personal rapid transit system for internal mobility. A PRT system with some 80 stations and thousands of vehicles was planned. Unfortunately, recent  (October 2010) announcements indicate that this plan has now been scaled back and the PRT system will be confined to a pilot system or a small system serving the area close to the Masdar Institute of Science and Technology. This is a blow to PRT proponents, but is PRT to blame for the setback?

Since PRT does not mix well with street level traffic, most urban plans call for an elevated PRT system with a very small ground-level footprint. This was considered at Masdar, but there was a chicken and egg problem. If the PRT was built first, it would be difficult to integrate it in the buildings to follow. Worse, all the costs would have to be borne by the developer. If the buildings were built first, they could be planned to accommodate and integrate the PRT system, and the building developers could possibly absorb station and other costs. Building developers were slow in coming forward and so the latter, preferable, option was not feasible, although it could possibly still have been accomplished by imposing carefully-planned building requirements (not easily accomplished in the prevailing culture). This, coupled with a desire to provide a pedestrian-friendly “ground” level, led to the decision to raise the pedestrian level, some 7 meters above the ground level to form a “podium” level, and to build the PRT system and the utilities in the undercroft formed below. Future buildings could then be constructed on the podium level with few restrictions.

Rubber-tired, battery-operated PRT vehicle, manufactured by 2getthere, being tested in the undercroft below the podium (pedestrain) level at the Masdar Institute of Science and Technology.

2getthere PRT vehicle in the Masdar undercroft

Putting PRT in the undercroft has proven problematic because:

  • The PRT routing was constrained to follow surface street routing, which is deliberately discontinuous to help prevent windy conditions.
  • The PRT routing is the same as that for special delivery (and, possibly, emergency) vehicles – violating one of the principles of PRT, which is to separate it from other traffic.
  • There is no way of enticing building developers to share the costs of the PRT stations and other elements.

The podium decision was made in more prosperous times. It is an expensive way to build a city, and current economic considerations have resulted in the decision being made not to extend the podium concept and the PRT system throughout the city. Thus the podium/undercroft decision underlies the decision not to extend the PRT system. Hopefully, the PRT system will soon come into successful public service, indicating that it can at least do the first part of what it was acquired to do.

Masdar is apparently considering electric cars and/or buses instead of the PRT system. It is difficult to imagine how this can be accomplished without revisiting the design parameters for the streets which are narrow and discontinuous. It may make much more sense to take a hard look at how an elevated PRT system could work and what it would take to merge it with the undercroft system.

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Personal Rapid Transit (PRT) and Risk

Saturday, August 14th, 2010

We often come across situations in the U.S. where managers are strongly motivated to avoid all risk (even small risks associated with potentially large benefits) and situations overseas where managers want to evaluate the risks and rewards. We believe the problem in the U.S. lies not so much with the individual managers as with societal expectations, the structure of their job and the way they are rewarded. The manager of a transportation authority must keep those buses and trains running despite increasing fuel costs and decreasing fares and subsidies. He/she is rewarded for implementing a glistening new light rail system and no one cares (or knows) if most of the passengers come from the reduced bus system. Were the light rail system to have a hiccup (delayed opening or budget overrun), the manager’s head may have to roll. No wonder the manager has no time, budget or inclination to look at an innovative system that has few successful operating examples he/she can kick the tires on.

Fortunately for personal rapid transit (PRT or Podcars), there are niche applications where small systems can be effective, such as airports, universities and other campus-like situations. PRT can (and is) make its debut and prove itself in these small applications. Transit managers will then see that it works and be emboldened to apply it in broader situations. Or will they? After a disastrous beginning, the Morgantown PRT system has been running very successfully (substantially beating conventional guideway transit by many measures) for over thirty years (the New York Times characterized it as “A White Elephant Turned Into a Transit Workhorse”) yet few transit managers seem interested in whether its success can be repeated without repeating its teething problems.

Without successful niche applications, PRT in the U.S. would be doomed until overseas applications have been operating successfully for twenty or more years. With successful niche applications, we may be able to stay close on the heels (say ten years behind) of our foreign friends.

How can a society be so risk averse and yet simultaneously accept extreme danger every day in their cars (we kill about as many Americans on the roads each year as were killed in the entire Vietnam War)? If we cannot learn to balance risk and reward, how are we going to ever regain the lead in transportation or any other field where we have lost it?

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Car-Free City Enabled by Personal Rapid Transit (PRT)

Wednesday, July 28th, 2010

Imagine a city designed to be free of cars, trucks and buses, yet to include a transportation system that will whisk its residents to any destination quickly and quietly without stopping. Children, the elderly, disabled and poor would have mobility similar to that currently available to the rest of the population.  The buildings could be much closer together, allowing easier walking, and/or they could accommodate more open space. The lack of accidents (personal rapid transit (PRT) is two orders of magnitude safer than current forms of transportation) would bring significant social benefits and greatly reduce the need for emergency services. Crime would be deterred, since the PRT stations and vehicles would be under constant video surveillance.

Some would argue that such a city would still need roads for emergency response, maintenance, refuse removal and large delivery vehicles. However, there are probably other (potentially better) ways of providing these services. Buildings could be sprinkled for fire suppression and equipped to facilitate emergency evacuation. Emergency personnel could utilize the PRT system, which would provide faster access than any present road system, and bring their personal gear with them. Special PRT vehicles could be equipped to accommodate gurneys and function as ambulances, while others could be equipped to support fire fighting. PRT freight vehicles could remove trash and deliver goods. Low-impact vehicles could deliver large goods by slowly driving down the pedestrian walkways, linking the buildings to each other and the PRT system. Some of the infrastructure savings could be used to fund helicopter services for extreme emergencies or exceptionally difficult movement of large items. All of these concepts need to be refined and incorporated in the new city’s building and planning codes, but none seem insurmountable.

Such a city couldbe made more sustainable by incorporating numerous additional low energy/emissions/waste technologies and yet be built for less than the cost to build a conventional city, since it would require less transportation infrastructure. Fewer PRT vehicles (and vehicle storage spaces) would be needed than the cars they replace, because each vehicle would make 50 to 100 trips per day. Even though the city cost less to build, its value would likely be higher than a conventional city. Studies have shown that the value of housing served by a good transit system is increased 6% to 45%, and commercial land values have been shown to increase 24% to 103%.

Residents would be able to purchase homes at a reduced cost and to reduce their automobile ownership. They would leave any cars they did own in parking facilities at the perimeter of the new city. Recreational vehicles would also be stored at the perimeter. Those with jobs in the new city would seldom use automobiles and thus lead much safer lives with reduced waste of time. Opportunities to use technology for improving many aspects of life, beyond just transportation, could help keep the new city almost free of crime and allow the residents to have a truly wonderful standard of living. It is finally time to take our cities back from the automobile and let them serve human needs once more.

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Hello personal rapid transit world!

Monday, April 27th, 2009

This is my first post and I have restricted it to simple housekeeping items. More substantive posts will follow soon. In the meantime, welcome to a whole new world of inter-connectivity!

Keep checking back for personal rapid transit (PRT) related posts soon.

Want to be in the loop? Keep up to date with the latest PRT posts – subscribe via email, RSS or Twitter by clicking on one of the links to the right.

Peter Muller

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