Representatives of the US Department of Transportation met in Washington DC last week for one and a half days to further advance their Memorandum of Cooperation with their Swedish counterparts on sustainable transportation. The officials from the two governments were joined by members of academia, consultants and suppliers/vendors. After joint meetings, subgroups met to discuss livability, multimodal station area planning, personal rapid transit/group rapid transit/automated transit networks (PRT/GRT/ATN) and railway technologies.

The four subgroups agreed that they all needed to collaborate since there is potentially considerable synergy between their areas of focus.

The PRT/GRT/ATN group agreed on a number of ways the two countries could work together to better understand and consider the potential for these technologies to help solve transportation issues. After the meetings, most members of this group toured the Morgantown PRT system after which Hans Larsen, San Jose Director of Transportation said, ““I (and I believe everyone in the group) thought the Morgantown PRT system tour was exceptional.  The system serves a very important transportation function for the Morgantown community.  It has high ridership and cost effective operations.  And it provides inspiration that automated transit is not a far out idea for the future; it works with 40 year old technology. “

The results of the meetings include the following:

• Agreement between the Cities of San Jose and Uppsala to coordinate and share information about their respective efforts to investigate and potentially implement ATN systems.
• Undertake workshops, surveys and develop a website to find out what people in different cities are looking for in transportation solutions (including their potential desire for ATN and estimates of probable ATN ridership).
• A strategic plan should be developed outlining how ATN could be leveraged to the best advantage of transportation overall in the next 30 to 40 years.
• Pursue more university collaboration.
• Develop an ATN planning guidebook (probably through the Transportation Cooperative Research Program process).
• Explore partnerships with private industry on development and manufacturing of ATN systems
• Help facilitate further research and development of ATN demonstration projects
• Seek a more comprehensive USDOT consideration of ATN as a compliment to existing transportation systems involving FTA (transit), FHWA (highways and parking), FAA (airports), and FRA (high speed rail).
• Convene sessions on ATN at the 2013 meeting of the Transportation Research Board.

Wednesday – Thursday 22^nd – 23^rd September 2010

I attended the morning tour of the PRT system thereby missing the first four Wednesday presentations. I had previously seen and ridden on the entire system. However, I had not seen the T-5 station since it was completed. It is an elegant and well-designed facility that appears to have ample space. Strolling around it, one appreciates some of the difficulties of designing for a system few will initially understand. For example, when passengers read “wait here for an empty berth” will they understand what a berth is and be able to determine where one ends and another begins? During the remainder of the tour and the ride the following morning (the system was closed for track maintenance on Wednesday morning), I paid attention to the opinions of others. Perhaps most telling was the comment of a Bombardier representative who indicated the system was much better than he had expected. I was interested in better evaluating the ride quality which, while not perfect, is definitely better than that in the back seat of a taxi.

Sven Beller, PTV AG, discussed the adaptation of existing tools such as VISUM and VISSIM to simulate PRT systems. Necessary adaptations can be scripted through the Application Programming Interface using other tools such as Excel’s Visual Basic for Applications.

Joerg Schweizer, Universita di Bologna presented work he is doing on a PRT Capacity Manual. The manual is intended to provide performance models that are quick and easy to apply with a focus on station operations.

Jochen Rabe, Associate, Ove Arup & Partners Ltd., said that comprehensive PRT networks covering entire cities may not be realistic. Local authorities must compare the transport service benefits of PRT with the visual impact and potential privacy loss.

Gabriele Giustiniani, Researcher, University of Rome ‘La Spienza’, outlined a CityMobil project with a round trip of 1.61km, 11 stops and 6 cybercars. He found the mode share for the cybercars was 10% more than that for a mini bus with the same schedule.

Steve Perliss, Lea+Elliott moderated a Procurement Workshop which included addresses from Bo Olsson, Senior Strategist, Trafikverket, David Holdcroft, PRT Manager, BAA, Martin Lowson, President, ULTra PRT, Robbert Lohman, Commercial Director, 2getthere and Jorgen Gustafsson, Managing Director, Vectus Ltd. Olsson described a two-step procurement process (first qualifications, then price) and said numerous questions must be answered before committing to a procurement process. Holdcroft described the process used to select ULTra. He said they received 15 responses. Lowson and Lohman implied they approved of the BAA procurement process. Perliss said it is important to give responders time to build teams and to bring them in early to get feedback. Ahuja said this is not possible in India where the tender period is limited to 6-8 weeks. Lowson and Lohmann agreed that the supplier must have control of the structural specifications to ensure ride quality and vehicle interfaces are adequate. Gustafsson said clear roles and responsibilities with simple interfaces and a lean organization able to make quick decisions (especially on the client side) were important. He said the Suncheon project will comprise 11km, 40 vehicles with 3M annual visitors. It will be mainly point-to-point and is being financed by Vectus who will receive an annual stipend. Muller pointed out that the workshop seemed to be moving towards guidance for consultants in preparing tender documents and that guidance for owners in moving from considering to implementing PRT was perhaps also needed. Lowson stated that, in his opinion, the ASCE APM standards are insufficient on the topic of safety and that safety clearance requirements vary greatly from country to country and even within some countries like the U.S.A.

Simon Babes, Director, Colin Buchanan, discussed a potential role for PRT in the Chinese megacity of Shanghai. He presented an analysis of a 20km, 20 station PRT system with 500 vehicles and 67,000 daily trips connecting a business park to a metro station. He anticipated fare revenues plus savings in shuttle bus operating costs could cover PRT operating costs and pay back the capital investment in five to ten years.

Richard Caple, Engineer Project Manager, Daventry District Council, said the major concerns for the Daventry PRT project include: visual intrusion; cost; anti-social behavior; ease of use and the complexity of the network. There is no funding presently available but he expects the system will happen eventually. He briefly outlined a document called Outlines for the Implementation of PRT in Urban Areas.

Peter Muller, President, PRT Consulting (the author), suggested that the true benefits of PRT will only be realized when it is used to develop entirely new cities built with a focus on ideal living conditions along with sustainability. He outlined how his vision for a “perfect” city could be enabled by PRT and recommended that those attempting to retrofit existing cities with PRT might want to keep this vision in mind, as something to strive towards. A poll of the audience revealed that about 75% would like to live in such a city.

Colin Bates, Managing Director, Customer Champions reported on a study of ULTra’s previous leads and key contacts. They found that the key barriers to sales were: risk aversion; desire not to be first (Heathrow will help but is not always applicable); urban developments are impacted by politics; PRT is not understood by decision makers; there is a lack of comparable data and proven benefits.

Malcolm Buchanan, Director, Colin Buchanan, summarized the conference. He asked if roads and cars or rail networks could eventually become PRT networks.

Tuesday 21^st September 2010

The Conference was opened by John Holland-Kaye, Commercial Director, BAA Airports, who said that the PRT system is obtaining 100% records for reliability. He was excited by the chance to create a new form of technology that will change the way people travel.

Fraser Brown, Head of Travel Services, Heathrow Airport Ltd – BAA, listed numerous advantages of the PRT system including: predictable; reduction in journey times; more than 70% have no waiting; reductions in emissions, noise and congestion; improved office rents, land values & availability as well as road safety. He is looking forward to a future where the passenger needs no local knowledge – they will not need to know where they have to go, just what they want to do. The system should be able to account for congestions, last-minute changes and delays in flight schedules.

David Holdcroft, PRT Manager, BAA, outlined completed and on-going system testing and passenger trials. He said that they have found out from passenger trials to date that passengers like the system. They also have learned that there are many aspects of the system that can be improved and have been tweaking such things as the audio message volume, door timings and button sequences. The on-going daily trials include passengers with luggage and are being used to monitor trends in the system status. The recent emergency situation rehearsal provided valuable lessons including that it resulted in duplicative responses from multiple jurisdictions. The system will open once BAA is satisfied with the results of daily trials and full integration of the PRT system with all other airport systems that could interact with it in any way. The integration process involves safety integration, new and updated operations protocols and familiarization of all potentially impacted airport staff.

Mark Griffiths, Head of Operations, ULTra PRT, continued the theme David Holdcroft started and told of unexpected passenger behaviors, such as going to an empty station berth to call a vehicle because they mistakenly assumed the one already waiting in a berth must be broken. He said they have a core staff of 24 for the 24/7 operation. Batteries must be recycled after about 3 months. Opportunity charging in stations allows a full battery pack to keep a vehicle running for several hours.

The Masdar PRT system had a two-hour test last week with 10 vehicles and 25 passengers according to Robbert Lohmann, Commercial Director, 2getthere. He said they put doors on one side of the vehicles only because doors tend to be problematic. However, this has required some special station layouts. When asked about rumors that Masdar is considering abandoning the PRT system for electric cars or other solutions, he said that Masdar is still committed to the PRT system but continually reconsidering their options because of the state of the economy.

Dario Menichetti with Mott MacDonald discussed the modeling of the MASDAR PRT system. They used conventional transportation modeling tools as well as a micro-simulation model in order to model the integrated systems and optimize the PRT topology and network performance.

Michel Parent, Team Manager, INRIA, said that cyber cars are fully-automated individual road vehicles that are part of an optimized transportation system but are not necessarily separated from other traffic. He described a cyber-car demonstration that will run for 6 months (January to June, 2011) with three vehicles in La Rochelle, France.

Tony Kerr, Director, Ove Arup & Partners Ltd., reported that they are now under contract and beginning work on the San José PRT project. The initial portion of the project will include investigating a PRT system connecting the airport to light- and commuter-rail stations.

Magnus Hunhammer, CEO, Institute for Sustainable Transportation described how they have used a full- scale portable PRT station to publicize and educate people about PRT. He also showed a PRT visualization.

John Hammersley with ULTra PRT discussed planning efforts and competition for a PRT system in the historic city of Bath. He said the competition led to overwhelmingly positive response and the PRT system could pay for operating costs and provide a return on investment of 7.3% based on a very reasonable fare.

Henk van Zuylen of The University of Technology, Delft described a PRT system connecting the Airport of Rotterdam and The Hague with existing rail and Scienceport Holland. The 21 km system would have 14 stations and 70 vehicles. Capital costs were estimated at €109M and annual O&M costs at €1.7M. He said the real barriers are institutional and political.

Sonal Ahuja, Director International Development, Capita Symonds Ltd., said there are 17 to 18 PRT projects currently being taken seriously in India where there is no recession and people pay for purchases in cash. He described a PRT study in New Delhi where they had to resort to double guideways to accommodate projected demand using 3 second headways and an occupancy factor of 3.0. The study showed a benefit/cost ratio of 4 and an internal rate of return of 18%.

Martin Lowson, President, ULTRa PRT discussed the design of a high capacity PRT station. He said they have found loading and unloading times to be quite consistent with that on other modes. Door cycle times tend to dominate station dwell times. Station designs can minimize the number of bays required by keeping standby vehicles close by in order to immediately replace departing vehicles.

Arturo Dávila, Project Engineer, IADIADA Automotive Technology SA, described a vehicle platooning system called SAfe Road TRains for the Environment (SARTRE) where the lead vehicle is driven and following ones are driverless. The intent is to increase safety and capacity while reducing energy used.

Ingmar Andréasson, Professor, KTH, discussed the ridership effects of PRT mixed with scheduled transit. He found that conventional transit is inadequate and PRT can increase total transit share and induce more travelling. In order to estimate the new transit share including PRT, all we need to know is the transit disutility and how much it is going to change, if the other modes are going to remain unchanged. He found the bus penalty relative to car to be € 2.50 and the PRT penalty to be half that, when the entire trip is by PRT.

There were four personal rapid transit (PRT) –related papers and/or presentations at the 89^th Annual meeting of the transportation Research Board (TRB) this year.

Martin Lowson, President of Advanced Transport Systems Ltd., (the developers of the ULTra PRT system) delivered an interesting presentation titled Preparing for PRT Operations at Heathrow Airport, United Kingdom. He showed a BBC video (not available in the US) where the reporter claimed to be the first member of the public to ride the system. ATS is still confident they can build complete systems for $10M to $15M per one-way mile.

Heathrow PRT Maintenance Facility

Professor Lowson said that BAA considered PRT to be the only practical solution to their many surface transportation problems. In addition to financial benefits, PRT offers a higher level of passenger service, environmental benefits and a more efficient use of space. He indicated they are well into phase Phase 3 of the following testing and implementation progress chart.

ATS has developed 429 system documents defining: Operations procedures (162), Safety Management System (75), Internal Management (74), Training modules (118). Professor Lowson showed the following slide depicting their safety verification process.

ATS has been surprised to find that passengers expect to share rides and want to wait for others to join them. The ULTra PRT system at Heathrow is in the final stage of test and commissioning and is on target for full passenger operations in mid 2010.

Steve Raney of Cities 21.org presented a paper titled Efficient Edge Cities of the Future and uniquely written in storey form that begins as follows: “October 5, 2020. Hello, my name is Emma Raney. Compared to typical suburban living, I live a life with lower cost of living; more free time; better work/life balance; stronger, more supportive, and more diverse local community; and one-quarter of the energy consumption. My community (SRP) produces emissions well below Kyoto protocol standards.”

The storey continues to describe life in a community that goes to considerable lengths to promote sustainability. Needless to say, the PRT system (a shuttle bus on steroids) is a key part of the community. However it is very much integrated into numerous other forms of accessibility.

Comprehensive Integrated Mobility

“SRP has a personal rapid transit (PRT) system, and I take that to many destinations… I carpool to church… SRP’s PRT connects to PRT systems in other large Silicon Valley office parks (there are 10 others). Via this connection, I connect to a larger variety of stores… Very rarely, I get a little carried away and I end up with a bunch of large items to schlep home. Large wheeled carts are available at some stores. I wheel the cart and items onto PRT vehicle, take my items home, then I wheel the empty cart onto another PRT vehicle where it is re-deployed… I take commuter rail to see Sharks hockey…When I go to Stanford for an event, I usually PRT with bike (on occasion I combine PRT with a foldable electric scooter). To get to places, I walk significantly more than a typical suburbanite – I generally travel the first and last trip segment on foot.”

Robert Baertsch, Nasa Ames Research Center presented a paper titled Renewable Energy Utilization Advantages of Maglev-Based Personal Rapid Transit. “This paper examines the advantages that Personal Rapid Transit (PRT) exhibits in the utilization of renewable energy from usage, distribution, and generation perspectives. The paper also looks at different types of PRT and how they impact the load on the electrical grid. Recent advances in power electronics and maglev technology allow for the design of a novel MPRT system characterized not only by exceptionally low power requirements, but also by a unique capacity to incorporate energy distribution and storage infrastructure into the greater transportation architecture.

MPRT prototype at NASA Ames, Moffett Field, CA

A hypothetical hybrid MPRT design incorporating energy storage and transmission capabilities is presented. Additionally, thorough carbon dioxide and cost analyses are undertaken in order to more fully understand the wide spectrum of benefits of an MPRT solution in comparison to Conventional Vehicle (CV) and Plug-in Hybrid Electric Vehicle (PHEV) approaches. We conclude that an MPRT system not only offers significant advantages over other technologies in efficiently utilizing renewable energy, but, moreover, that the unique potential of this concept to incorporate power transmission, storage, and generation infrastructure makes it ideal for addressing the energy challenges of the near and distant future.”

The system is anticipated to operate at 40 mph in downtown areas and at highway speeds elsewhere. The upper speed limit is 150 mph. Linear induction motors are built into the guideway. An equivalent 325 mpg and capital costs under $10M per one way mile (up to $18M including integrated photovoltaic panels and power distribution) are anticipated.

John Lees_Miller, University of Bristol, United Kingdom presented a paper titled Theoretical Maximum Capacity as a Benchmark for Empty Vehicle Redistribution in Personal Rapid Transit. “A Personal Rapid Transit (PRT) system uses compact, computer-guided vehicles running on dedicated guideways to carry individuals or small groups directly between pairs of stations.  Vehicles move on demand when a passenger requests service at his/her origin station. Because the number of trips requested from a station need not equal the number of trips ending there, some vehicles must run empty to balance the flows. The empty vehicle redistribution (EVR) problem is to decide which empty vehicles to move, and when and where to move them; an EVR algorithm makes these decisions in real time, as passengers arrive and request service.

This paper describes a method for finding the theoretical maximum demand (with a given spatial distribution) that a given system could serve with any EVR algorithm, which provides a benchmark against which particular EVR algorithms can be compared.  The maximum passenger demand that a particular EVR algorithm can serve can be determined by simulation and then compared to the benchmark. The method is applied to two simple EVR heuristics on two example systems, and the results suggest that this is a useful method for determining the strengths and weaknesses of a variety of EVR heuristics across a range of networks, passenger demands and fleet sizes.

This paper demonstrates a new method for the evaluation of empty vehicle redistribution (EVR) algorithms, providing an absolute measure of their performance according to a metric based on the capacity region for a given network. The capacity region is defined as the set of OD matrices which are feasible in the sense that their demands can be met without passenger queues growing indefinitely.  It describes the maximum possible demand that a particular system could serve with an ideal EVR algorithm, and hence acts as an absolute benchmark against which different EVR algorithms can be compared.

The ability to compare and evaluate EVR algorithms is important for the successful operation of highly-connected PRT systems…  In normal PRT operation, the minimization of passenger waiting time is usually the priority, and hence one could expect an EVR heuristic which prioritizes this…to be in operation.  At times of high demand, however, when the vehicle fleet is stretched and there are passengers waiting at numerous stations across the network [this]… often moves vehicles too far.  One would instead prefer an algorithm which prioritizes the efficient use of the vehicle fleet…

This analysis also shows how both the network topology and the spatial distribution of the demand can affect EVR performance, even when line congestion is ignored…The proposed method allows for the absolute assessment of EVR algorithms in terms of throughput, subject to the modeling assumptions…There are a number of alternative heuristics already present in the literature … and an analysis of these algorithms using this evaluation tool is a natural next step.”

Transportation is Broken – a New Solution is Needed

A review of the major characteristics of our urban transportation system quickly reveals that it is thoroughly broken. Of even greater concern is the fact that most of the solutions currently gaining traction will do little to solve the most pressing problems.

The problem

Let’s start by comparing how various indicators have grown relative to population growth over the past 20 years. Table 1 lists major transportation characteristics and their growth over a 20 year period. The horizontal red line shows the U.S. population growth over that time (about 24%), and the discussion below compares the growth of each characteristic to the population growth, in order to put things in perspective (if nothing changed, these characteristics could all be expected to grow at the same rate as the population has grown).

Accidents. The total number of accidents has actually declined. While this is the only factor to decline, and clearly a good thing, it is still not nearly enough. Over 40,000 people are still killed on US roads annually (compared with total U.S. deaths in Vietnam – 58,159; Iraq – 4,334; 9/11 – 2,993), and road traffic injuries are one of the top three causes of death for people aged between 5 and 44 years worldwide. Lest you think the US is much safer than the rest of the world, we are not. There are approximately 60 countries with lower death rates per 100,000 population. Improving safety is no easy feat, since advances in safety technology can be easily offset by societal changes, such as texting while driving.

Use of Public Transportation. Transit use grew a little more than population but much less than passenger vehicle miles traveled. Try as we might, we just cannot convince people to leave their cars for transit. During the recent period of high gasoline prices, a small jump in transit use was experienced. This caused problems for transit agencies around the country, because they lose money on each rider! This unsustainable practice was exacerbated by reduced tax-based subsidies and meant that many agencies had to reduce service at the precise time they should have been increasing it. Subsidized transit systems may be necessary to ensure that the disadvantaged have reasonably priced transportation. However, a sustainable transit system, that can rise to meet changing demand, needs to cover at least its operating expenses from the fare box – something that few US transit systems can accomplish.

Transportation Energy Use. This is growing an alarming 50% faster than the population and a large portion of this energy comes from foreign oil suppliers. 96.6% of all transportation energy use is petroleum-based and any growth at all is problematic. As cheap oil resources are depleted, and as countries such as India and China dramatically increase their oil use, cost of oil is likely to rise steeply and cause serious problems for transportation.

Delays Caused by Congestion. As more and more cities face rush-hour gridlock (and rush-hours get longer and longer), this factor is growing twice as fast as the population and congestion now wastes 3.5 billion man-hours every year. We do not seem to be able to build ourselves out of this problem. Consider I-25 through Denver; Two years after a major improvement project took it from six to eight lanes plus light rail, it regularly suffers congestion similar to what it did before the construction. Paradoxically, even in bad traffic, the light rail train seldom passes the automobiles. This is because the light rail system only averages under 25 mph. By the way, the light rail’s two lines cost about the same to build as the eight lanes of highway, even though they carry much less traffic.

Passenger Vehicle Miles Travelled. The amount of driving we do is outgrowing the population by almost three times! This high level of passenger vehicle use is widely seen as being unsustainable. The energy used (and the related foreign oil dependence) is seen by many as being the major issue. However, automobile use brings numerous other problems. While accidents and congestion are discussed separately, two other problems are real estate/infrastructure and automobile manufacture. Each car typically requires four parking spaces (one at home, one at work and two others for intermittent use). The cost of this infrastructure (these spaces are typically paved and often roofed) and the street/road/highway infrastructure, needed to support our automobile use, is enormous. At the same time, the real estate used to support automobiles increases the cost of other utilities and decreases the quality of urban living. Furthermore, the cost of highways is increasing as design standards are continually raised in an attempt to reduce accidents. In addition, the tax revenue to support this infrastructure has not kept pace with the need, and we are likely to face increased taxes and/or more and more tolled highways. The cost to society of individual automobile ownership is rising as we strive to make cars more sustainable. It’s time we took a long hard look at what automobile ownership really costs.

Logistics Costs. These are the costs of moving goods and they have increased far faster than the population has grown. At this pace, logistics costs are set to have major impacts on our economy. Part of the reason is that we move a very large proportion of goods by semi trucks rather than rail. Rail is a far more efficient way to move goods, but we lack the infrastructure to economically collect and distribute goods at the ends of the rail lines. Shipping suffered from a similar problem, wherein the cost of handling goods in harbors exceeded the cost of shipping them over the seas. This changed with the advent of container ships. A similar revolution is needed for rail.

Greenhouse Gas Emissions. Transportation accounted for 47% of the net increase in total U.S. greenhouse gas emissions since 1990. It currently contributes 34% of all greenhouse gas emissions. Reducing transportation-related greenhouse gases requires reducing the amount of energy used by transportation, as well as changing the primary source of that energy.

A solution

Think transit is the solution? Think again. In the U.S., transit uses (wastes) as much energy per passenger mile as the automobile. This is largely because trains and buses run around empty most of the day. Transit infrastructure is expensive to build, consumes much real estate and resources, and its construction contributes significantly to greenhouse gases. High speed rail and air travel may be good solutions for long distances, but both suffer a last mile (or last many mile) problem and do nothing for urban mobility.

It is amazing to think that we are still using the stagecoach model for transit. A stagecoach runs on fixed routes with designated stops. There is seldom a stop at the desired origin and destination (the first/last mile problem mentioned above). The vehicle accommodates many people, to spread the cost of the driver, and has to stop whenever somebody needs to get on or off. All we have done to this model is make the vehicles bigger, turn the stops into stations and the routes into corridors. The ride may be a little smoother and the speed a little higher, but the quality of service has hardly improved. A rail system, with top speeds in the fifties and stations every mile, has an average speed under 25mph. “Modern” street cars often have average speeds in the single digits. It is no wonder transit only achieves a mode share of around 4%. The model is broken and we need to quit trying to fix it. We need a new model.

What if you did not have to wait for transit, you always got a seat, and it took you where you want to go without stopping? Would you use it? The only mode of transportation that currently operates this way is the automobile at 3a.m. Even then, stops at “dumb” traffic signals for no crossing traffic at all are often required. Amazingly enough, transit that operates this way was invented over fifty years ago. It is called personal rapid transit (PRT) and it can be likened to automated (driverless) taxis operating on a system of guideways. The reasons PRT could help solve our transportation problems are:

1. It has a high level of service (more like a car than a bus) and really can attract drivers from their cars.

1. It uses about a third the energy of most other modes.
2. It is electrically powered so, as we convert the grid to renewable sources of energy, we automatically also convert PRT-based transportation.
3. It has proven to be about a hundred times safer than conventional transit.
4. Elevated or buried (PRT tunnels are much smaller to move the same number of people) guideways do not use up real estate or cause neighborhood severance.
5. Small vehicle sizes (like a small automobile) require minimal infrastructure.
6. Each automated T-Pod (transportation pod) will be reused fifty or more times a day – an efficient use of manufacturing resources and a reduced need for parking.
7. In off-peak times, unused T-Pods wait in stations or depots – there is much reduced empty vehicle movement.

Table 2 below shows my opinion of the extent to which various solutions are likely to have a positive impact on the transportation problems mentioned at the beginning of this discussion. 0 = no impact, 1 = some impact, 2 = significant impact. Certainly, some will argue with my ratings, which are based on my own opinions and analyses. In addition, PRT has yet to be proven in large applications. The point is that PRT appears to have the potential for quite significant impacts across the board, yet it is receiving attention that is dramatically disproportionate to this potential.