Flow to Stability

Monday, September 21, 2015

The Seed and the Harvest: a long-term vision for the role of Gulf Oil Exporters in the Global Energy Transition

The seeming paradox of oil-exporting Gulf countries pursuing a renewable energy diversification agenda has been discussed extensively in this journal (cf. OEF Issue 96) and elsewhere. The ACWA Power bid in Dubai was the first project in the world to break the six cents per kWh for a competitive, unsubsidized tariff. As such, it brought the prospect of solarization in the Gulf Cooperation Countries (GCC) forward at a rate that exceeded even “optimistic” expectations[1]. Nevertheless, the level of current and planned RE penetration is small compared to the potential. In this paper, we look beyond the short- and medium-term horizon and investigate the role that GCC could play in the long-term, global, sustainable energy transition. We argue that accelerated adoption of RE in these countries is not an existential threat but a way of securing a role as an energy exporter in a world fueled entirely by renewable energy.

Such a world is much closer than many realize if we are to have a reasonable chance to stay within the 2C average temperature rise threshold. This target implies that the bulk of the fossil fuel phase-out would need to occur by 2050-2080 depending on the assumption of the CO2 emissions budget. IPCC gives a wide range for this budget from around 500 to 1500 GtCO2 with a 66% likelihood value of 990 [2]. At face value this means that GCC societies  would be forced to radically transform their economies in a span of just two generations mirroring the lighting fast ascent from poor nomadic societies into the richest countries in the world on a per capita basis.

It is unsurprising that the prospect of such transformation triggers discomfort and an almost instinctive reaction to fight back. So, it is to the credit of the Gulf energy exporters that their governments, for different reasons each, have to a large-extent, embraced the need to act against climate change although they refrain from leading this effort. I argue that it is in the interest of GCC energy exporters to move from the sidelines and instead lead the charge for the following three reasons.

First, given the high quality of the fossil resource base, their extraction rates and exports are the least affected by carbon curtailment among all energy producers. Second, there will be a temporary but noticeable increase in the demand for the fossil fuels that these countries produce in order to fuel the transition from fossil to renewables. Third, from a strategic perspective it is better to be actively involved in a change that should come anyway than react to it as the delay entails the risk of missing out at the opportunities created by the transition.

Growing Fossil extraction rates for GCC under climate constraints

Looking deeper into the first statement, we note that not all fossil fuels are equal. They differ with respect to their marginal extraction cost in a way that generally reflects physical properties that can be summarized in a metric like the energy return on energy invested (EROEI) [3]. The non-conventional resources like tight oil, shale gas, tar sands, and deep-sea oil all have a higher marginal cost of extraction reflecting the fact that they are harder to extract, transport, and/or refine into useful products. In a recent paper, McGlade and Ekins [4] attempted to map the geographical distribution of the resource that could be extracted under the carbon constraints by overlaying the safely recoverable reserves with the marginal cost of extraction of a given formation or type of resource. They offer two estimates one with Carbon Capture and Storage (CCS) and one without.

Since a large number of the 2C compatible scenarios rely on CCS (even using biomass for taking carbon out of the atmosphere during the second part of the century), it is necessary to parenthetically elaborate why we do not consider this option viable at scale and in time. CCS in electricity power plants, as opposed to industrial processes, imparts a significant operational energy penalty for the capture, compression, transport and injection of CO2 into geologic formations that is around 40% with the current dominant technology (amine-based, post-combustion capture) [5] and somewhat less for oxy-combustion systems. In addition, it requires heavy capital investment further deteriorating the EROEI of the resource. Given that even proponents suggested that “[t]ens of large CCS demonstrators need to be built worldwide from 2009[6] when only one CCS power plant is operational in 2015 [7], it is evident that the window for scaling up CCS in order to support the energy transition is closing.

Focusing, therefore, on the analysis without CCS deployment, they estimate that the unburnable part of the Middle East oil and gas reserves are 38% and 61% respectively by 2050 allowing for additional extraction beyond that date. For comparison, Canada would have to leave 75% of its oil reserves unburned and all coal regions would need to keep more than 80% of their coal in the ground. The practical implication of this allocation for individual ME producers in terms of extractable reserves is that, assuming an equal allocation across countries, shown in Figure 1, all three of the top producers would be able to increase their annual oil extraction from 13% for KSA to 60% for Kuwait and still stay within the extractable limits.

Figure 1 Daily Average crude oil production in 2013 compared with the daily production level at which the 2C-compliant extractable reserves are exhausted by 2050 (in Mbbl/day)

The Seed of the Energy Transition

This ability to increase fossil fuel extraction may still look counterintuitive and detrimental to the climate cause, but the realities of the only alternative energy supply that can scale, renewable energy or RE, require an upfront energy investment in order to be constructed. This energy investment subtracts from what we might call society’s operational energy budget creating an energy deficit. Fossil fuels are the sole viable option for balancing this deficit and providing the “seed” investment in a flexible way.

Historically, energy transitions were partial affairs lasting several decades [8]. In some respects they would be more appropriately classified as substitutions since looking at the nominal amount of energy provided, most primary energy sources that humanity exploited have expanded – just their utilization changed. Coal, for example, still powers our trains and heats our homes, just more effectively by centralizing its combustion in electricity power stations than the less efficient distributed use in steam engines and boilers while the global amount of energy provided from biomass and biofuels is higher than ever before. The reality is that we don't have any historical precedent for the massive scale transition required to move from fossil fuels to renewables, especially when the bulk of this transition needs to take place in the next four decades and effectively phase-out almost all fossil fuels during this century.

Given that we are emitting around 35GtCO2 per year without a visible slowing down yet, the phase-out of fossil fuels will need to be abrupt. In order to prepare for this and to avoid precipitous changes in the energy supply that would cause social dislocation, we need to phase-in the appropriate RE capacity with advanced planning. By applying an energy balance approach to the constraints of the energy transition [9], we find that RE installation rates should increase by a factor of 30, from 0.2TW/year in 2013 to 6TW/year in 2040 but even higher numbers may prove necessary. When RE installations accelerate at such rates, the investment consumes more energy than it produces[10]. As a result, in order to compensate, the energy system will need to rely on fossil fuels to provide what we call the seed in the sower’s strategy of the energy transition.

In other words, the forthcoming energy transition, if it is to be sustainable, cannot be expected to occur organically and without a significant degree of advanced planning, for three principal reasons: (i) the potential of depowering, i.e. decreasing economic energy intensity, is limited if any, (ii) there are no past global or regional scale energy transitions to act as guidance, and, critically, (iii) climate change mitigation imposes very tight constraints on the remaining amount of fossil fuels that can be safely used.

As a result of the above, fossil fuel exporters are called to play a vital role in fueling and shaping this global undertaking which we call the sustainable energy transition (SET). While SET spells bad news for marginal oil producers like tight oil, deep-sea, and tar sand plays, as explained in the previous section, it relies on the production of oil and gas reserves with low extraction costs to support the early years of accelerated RE expansion in a way that does not cause severe economic dislocations.

Sustaining an Energy Exporter Status in a Renewable Energy World

Beyond simply powering the energy transition by exporting their fossil fuels, GCC countries have the opportunity to become a sustainable energy exporter if they choose to leverage their capital to build out the necessary infrastructure. Even in an RE-based world, there will be a constant need for high density energy carriers to power processes that cannot be easily electrified (e.g. airplanes, ships and trucks) as well as raw materials for the production of plastics and fertilizers.
The GCC countries could act proactively to meet this demand by building the necessary, large-scale, infrastructure. They would do so by capitalizing on their sun-belt RE potential and convert this locally generated electricity into a transportable, energy-dense fuel.

In order to put this in context, we provide an example on what it would mean in the case of the UAE. In Figure 1 we assumed that extractable reserves would be produced by 2050 at a constant rate. Given that neither field production dynamics nor economics indicate a rectilinear production, a logistics curve production extending further after 2050 is far more likely. This profile, known as Hubbert curve approximation [11], can be applied to show the unconstrained and the constrained extraction rates for oil and gas resources of the UAE until the end of the century (Figure 2).

Figure 2 Oil and natural production profile for the UAE following a Hubbert curve approximation with the addition of a solar-based electricity to ammonia system in TWh (developed in collaboration with Denes Csala)

The darker shade trapezoid that reaches to about a fifth of the peak production, shows the amount of synthetic fuel that could be produced if 10% of the UAE’s land area is utilized for large-scale photovoltaic plants dedicated to an electricity to liquids process. This area could accommodate around 350GW of installed PV capacity that would drive a system of large-scale electrolyzers for hydrogen generation, along with nitrogen from air separation units. Their combination would produce ammonia (NH3), an energy carrier that has higher energy density than liquid hydrogen with lower storage costs [12]. Ammonia can be exported and used by direct combustion, through a fuel cell or as a critical input for fertilizer production. An interesting synergistic option is offered for the utilization of the oxygen byproduct from the air separation units. The oxygen stream could be used for a natural gas oxycombustion carbon capture system with the resultant CO2 being either stored or used as feedstock for hydrocarbon synthesis in a Fischer-Tropsch system. In either case a larger amount of natural gas could be utilized than the 39% permitted under climate constraints. This rough concept is intended to demonstrate the possibility of using the Gulf’s RE potential not simply to support the local economy in the post-oil era but also to offer a significant, sustainable resource of liquid-fuels that can allow these countries to maintain a position as net-energy exporters. Whether it would take this form or another, it is an option that the GCC countries need to seriously consider as the window for building out such a system requires abundant capital and lengthy pilot testing.

Moving back from this long-term vision, like all journeys, the energy transition in the GCC requires firm initial steps. A possible pathway for these initial adoption phase was developed as part of global REmap, an effort led by the International Renewable Energy Agency[13]. Institutional change along the physical infrastructure is necessary. Some key initiatives could include:
·      revising the take-or-pay clauses with the independent power and water producers (IWPPs) into capacity reserve agreements that would adjust as needs change,
·      increasing the flexibility of water production to maximize the efficiency of the legacy multi-stage flash plants by leveraging the development of strategic water reserves and moving all new desalination capacity towards electricity-driven reverse-osmosis systems,
·      pricing internal resources in a way that reflects the opportunity cost for the country.
Changes along these lines supplemented by clarification of land-use and allocation of areas for utility scale RE plant development would nurture the RE expansion rate necessary for the countries to become truly sustainable and energy leaders in a transitioning world without having to provide subsidies.

Sustainable Investments in an Volatile World

While the Gulf countries continue to maintain positive trade balances, the 2014/15 drop in oil prices from a fairly constant $100 to less than $38 per barrel in August 2015 has instilled concern about the long-term finances of these countries. It is possible that this precipitous drop is a result of a deflationary spiral dynamics as monetary expansion in the financial system is constrained by stopping quantitative easing. This curtails debt financing reducing the amounts available for discretionary spending worldwide, which in turn impacts manufacturing output and their resource consumption. A byproduct of a financialized economic system [14], such a deflationary spiral is not caused by actual physical shortages of energy or other resources and therefore it is possible that another cycle of economic expansion will push prices up especially as some of the marginal producers will have been pushed to bankruptcy.

As a result, the next cycle of expansion, if it materializes, is perhaps the last viable chance to make a global energy transition sustainable. The fuel exporting countries can lead the way with proper direction of their investment not only in financial products but also in physical assets located on their territories. Done with foresight, such investment would allow them to secure a sustainable future as energy exporters and create resilient local infrastructures that can thrive even after oil and natural gas become unburnable globally. To do so, it is imperative that development of RE projects and energy efficiency infrastructure needs to begin in earnest. Given that RE already makes economic sense for electricity generation, it is a matter of overcoming institutional inertia and apprehension as well as rethinking the energy system structure in order to accommodate higher RE penetration.

In closing, when the economic system becomes limited by energy constraints, as those imposed by the specter of a global climate catastrophe, the rule of limited resources and increasing complexity that has doomed the empires of the past will become relevant again. If we want to prevent a collapse, we will need alternative energy sources to support us as we attempt to solve the problems inherited by building a complex civilization. Historian Joseph Tainter eloquently describes the implications from this tendency for complexity to beget complexity and the need for energy availability to resolve them:

“[I]n addressing the problems of global change, our societies are likely to become more complex and more costly. We need the wealth that can be provided by greater availability of energy to finance greater complexity, including more research, more education, more regulation of environmental matters, and new technologies.” [15]

The GCC fossil exporters are therefore positioned to be a key contributor in solving this critical future energy puzzle by providing low-impact fossil resources for moving to a renewable energy world. Not only that, but looking at the sustainability of their economies and with forward-looking investments, they could maintain a global position in the energy system as providers of a renewable stream of energy carriers taking advantage of their access to capital and solar resource potential.

[1] S Sgouridis et al., ‘RE-mapping the UAE’s energy transition: An economy-wide assessment of renewable energy options and their policy implications’, in Renewable and Sustainable Energy Reviews,, 2015, 1–15.
[2] IPCC, Climate Change 2013: The Physical Science Basis, in, Cambridge University Press, 2014.
[3] CAS Hall, JG Lambert & SB Balogh, ‘EROI of different fuels and the implications for society ’, in Energy Policy, vol. 64, 2014, 141–152.
[4] C McGlade & P Ekins, ‘The geographical distribution of fossil fuels unused when limiting global warming to 2’, in Nature, vol. 517, 2014, 187–190.
[5] KZ House et al., ‘The energy penalty of post-combustion CO2 capture & storage and its implications for retrofitting the U.S. installed base’, in Energy & Environmental Science, vol. 2, 2009, 193.
[6] RS Haszeldine, ‘Carbon Capture and Storage: How Green Can Black Be?’, in science, vol. 325, 2009, 1647–1652.
[7] GCCSI, ‘Large Scale CCS Projects’, in, Global Carbon Capture and Storage Institute, 2015, pp. 1–5, .
[8] R Fouquet, ‘The slow search for solutions: Lessons from historical energy transitions by sector and service’, in Energy Policy, vol. 38, 2010, 6586–6596.
[9] S Sgouridis & D Csala, ‘A Framework for Defining Sustainable Energy Transitions: Principles, Dynamics, and Implications’, in Sustainability, vol. 6, 2014, 2601–2622.
[10] M Dale & SM Benson, ‘Energy Balance of the Global Photovoltaic (PV) Industry - Is the PV Industry a Net Electricity Producer?’, in Environmental Science & Technology,, 2013, 130312080757002.
[11] AJ Cavallo, ‘Hubbert?s petroleum production model: an evaluation and implications for World Oil Production Forecasts’, in Natural Resources Research, vol. 13, 2004, 211–221.
[12] C Zamfirescu & I Dincer, ‘Using ammonia as a sustainable fuel’, in Journal of Power Sources, vol. 185, 2008, 459–465.
[13] Sgouridis et al., 1–15.
[14] C Lapavitsas, Profiting Without Producing, in, Verso Books, 2014.
[15] JA Tainter, ‘Sustainability of complex societies’, in Futures, vol. 27, 1995, 397–407.

Monday, September 15, 2014

The unrealized potential of Personal Rapid Transit

An older piece I wrote for EPFL Network Industries Quarterly. Still relevant though.

A personal driver-less vehicle, along with the flying car and lunar cities (Milo 2009), is one of the concepts that failed to be delivered on time from the optimistic prognostications of the 1950s and 1960s. While that future is yet to come, the technologies for the eventual deployment of personal rapid transit (PRT) are being advanced. In this article I review the vision, the current status of PRT systems and related technologies and examine the potential, the advantages and the disadvantages of such systems for urban transport.

The vision
The defining characteristic of a PRT system is a small-sized driverless vehicle that operates on demand (The require- ment adopted by the Advanced Transit Association for separated right of way is too restrictive.) A PRT system aspires to combine the on-demand and private space ad- vantages of a personal car with the convenience and effi- ciency of a transit system. PRT operating models can span the spectrum from a purely public system with stations, to car sharing pods (a zipcar with no driver that picks you up at your door through prior arrangement and delivers you at your destination) to privately owned automatic cars. The PRT vehicles operate at the same level of separation as roads and trams from pedestrians and non-motorized traffic.

While in operation all-electric PRT vehicles can create virtual trains by “tailgating” with very short headways at distances of half a meter or less, moving at high speeds while using narrow lanes. A PRT system requires no traf- fic signals visible or otherwise, yet congestion is a virtual unknown and throughput is close to the maximum of the free flowing traffic. When stopped, their batteries act de- pendably as a grid stability mechanism and their owners are compensated accordingly.

The bits and pieces
Reaching anywhere close to that vision requires impecca- ble communications and optimization algorithms as much as transportation hardware.

For the physical infrastructure, a PRT system does not really require significant investment if it can utilize the ex- isting road infrastructure. One thing that is sine qua non is very accurate positioning, which can be achieved by a combination of satellite positioning, on-board measure- ment devices and roadside markers. The vehicles them- selves need to have a suite of vicinity-sensing equipment, i.e. radars, that create the awareness bubble of the vehicle effectively leaving no blind spots.

On the software side, things become more complicat- ed. For a large-scale system implementation, as opposed to individual robotic vehicles, seamless coordination between vehicle control and transport-system operations is an absolute requirement. Without such coordination, the sys- tem performance cannot achieve the efficiency improve- ments that would make it worthwhile nor reach the very high safety and reliability standards that would be required for widespread adoption. This requirement for communi- cation implies high computational power both on the ve- hicle and on the control system.
There are three schools of thought on how the PRT system operations would be organized:

centralized (synchronous), distributed (asynchronous), and hybrid.

Centralized systems operate with minimal intelligence on the vehicle aside from obstacle detection and guidance con- trol. All vehicle operations, including navigation, junction negotiation, and scheduling, are performed centrally. This creates the need for the central system to have rapid, real- time updates of the system status and the ability to compute and direct the optimal trajectories for perhaps thousands of vehicles. Distributed systems, on the other hand, are bottom-up relying on peer-to-peer communication and priority negotiation based on preset rules akin to the proposals for future generation air-traffic control system. Distributed intelligence eliminates the need of the central system making operations robust and self-organizing. Intuitively, the hybrid systems fall in between, allowing for low-level functions to be performed locally (thus removing the requirement for high-bandwidth real-time communications to the central system – updates over the span of a minute with higher level information would be sufficient) but at the same time allowing for system-wide optimization; thus, they seem to be the more likely systems for widespread adoption although there is a debate on their relative merit [cf. (Fernandes and Nunes 2010), (Anderson 1996)].

The potential advantages of a PRT system can be categorized into efficiency, safety, and convenience.

The main thrust of efficiency improvements are achieved through system-wide coordination, i.e. the primary efficiency gains come from the system operations. Firstly, there is the ability to create virtual vehicle trains where the air drag is reduced substantially for the following vehicles, a feature that can be useful for urban high-speed motorways.

Yet, more important is the ability to optimize intersection and on-ramp behavior negating the need for stopping and the energy and trip time inefficiencies associated with it. Additionally, congestion, the very costly in time and energy transportation system behavior emergent from the interaction of overreacting human operators, can be mitigated. PRT systems reduce incident occurrence that is a trigger for congestion and, as all vehicle trajectory vectors are known, it can redirect or slow vehicles to match free-flowing traffic conditions in the instances where demand still exceeds available capacity. Finally, as vehicles operate on demand, there is efficiency potential from the increased load factor, especially if a car- pooling function is enabled. This potential, though, is counterbalanced by the need to potentially reshuffle the empty vehicles to match peak demand.

On the vehicle side, accident probability reduction can allow the vehicles to become lighter again by value engineering some of the heavier passive safety features. Moreover, in a car-sharing PRT system, the equipment utilization – the amount of time that the vehicles are used – is much greater than in the case of private cars.

The assumption of safety relies on system design. Theoretically, the continuous vigilance of PRT vehicles would eliminate the major cause of accidents, which is the human factor alone (57%) or in combination with vehicle and roadway factors (37%) (Lum and Reagan 1995) (Rumar 1983). Driver aggression, inattention or impairment (e.g. speeding, running red light, texting and talking on the phone, driving under the influence, etc.) would become irrelevant. Of course it is possible that other factors due to system complexity could induce new failure modes (cf. Pitfalls section), but as long as the vehicles are equipped with multi-level safety systems that can operate passively, there are ways to address these concerns.

The single most attractive feature of the PRT systems for the user is their convenience. Travelers can expect to minimize trip time due to the door-to-door congestion- free ride. Moreover, they can expect to utilize the actual travel time to their benefit – communicating or working without worrying about operating the vehicle.

Technology dreams, especially those that require massive transitions, can be transformed into impossibilities or nightmares depending on the confluence of economic, technical, and social factors which are discussed in some more detail below.

PRT systems today can be expensive (cf. Masdar section) but this is true for any prototype system. The question is whether initial adopters can capture the advantages out- lined above in a way that provides sufficient recouping of the investment that will allow widespread adoption and volumes to make learning and scale economies possible.

Complexity and Catastrophic Failures
The failure modes of complex, tightly coupled systems can be surprising and inherently lie in the design of those sys- tems (Perrow 1984). Therefore, an important disadvan- tage of a PRT system would be these potentially unpredictable failure modes due to its complexity. The same can be said for the Internet. Unlike the Internet, which is massively parallel and does not control physically thousands of people moving at homicidal speeds, a PRT system can fail spectacularly with catastrophic consequences. Such an event, although highly unlikely, cannot be ruled out but at least can be engineered against massive death tolls, though not necessarily against massive gridlock. In principle, the decoupling and subsidiarity provided by hybrid and distributed PRT systems would make them less susceptible but not immune to these types of failures.

A further complication stemming from the probability of failure is the regulatory handling of liability in that case. Until safety systems are proven, other features like the very short headways and traffic integration will probably not be permitted for commercial operations.

Acceptance and Control
Even a perfectly functional system can be hindered if its users do not accept it. The primary area of user concern would be related to the feeling of lack of control and as- sociated safety concerns but also to the fun and prestige factor of driving a vehicle. The statistical misconception that leads the vast majority of drivers to claim that they are better than average would be active in this case. Even a minor incident, could be magnified. Yet, actual practice shows that people accept to be driven by other human drivers, ride in mass transit and even driverless vehicles without much apprehension.
Other aspects of lack of control are probably going to be more of a concern in the longer term: namely privacy, potential for malicious attack and hacking, and higher government control over transport. Privacy issues relate to the fact that identifiable travel information about the user of a PRT vehicle can be collected. Most users of a phone have already surrendered the privacy of their calls and a functioning democratic government can place enough oversight to mandate anonymization, thus facilitating ac- ceptance. Yet, this same controllability and IT-reliance makes the PRT system a prime target for malicious hack- ing attacks, given its potential for high-visibility disrup- tion. And for those less willing to assume benevolence on the part of the government, the fact that all vehicle opera- tions can be directed centrally could mean that it can be- come a tool in the hand of government for impeding civic demonstrations by freezing transportation towards a par- ticular location.

The Jevons’ Paradox of Mobility
Interestingly, one of the adverse effects of a PRT system could come from its success. Jevons observed in the early 19th century that when the efficiency of processes utiliz- ing coal increased, coal consumption – counter-intuitively at first glance – also increased (cf. (Alcott 2005) for an overview). The phenomenon, also known as induced de- mand or rebound effect, is by now well established and can apply to transport. As the travel time budget has re- mained remarkably consistent across centuries (Schafer and Victor 2000), travelers tend to use the extra speed of travel to increase the distance traveled. Similarly, PRT’s convenience and time efficiency, by allowing travelers to reduce their perceived trip time and expenses, can induce users to opt not only to increase travel with a private PRT compared to a private car but also shift travel away from traditional mass transit if the price and availability of PRT systems are right.

Current incarnations
The discussions above may sound premature, but the real- ity is that PRT systems have started to transition from ideas to materiality. The honorable mention has to go to the first and oldest operating transit system called a PRT: located in Morgantown, West Virginia, it is operating like a small on-demand rail line and has gained appreciation for its convenience (Hamill 2007). Yet, three more recent and ambitious cases of implementation are: Rotterdam Port, Masdar City, and the Google Car. Other notable developments include the Heathrow Airport PRT and the newly announced GM EN-V prototype.

Rotterdam Port
The automated guided vehicles (AGVs) that operate the container transport at Rotterdam port are not technically a PRT but they provide a good illustration of a complex, multi-vehicle automatic system operating efficiently and profitably (Figure 1A).

Masdar City
The Masdar City is a futuristic and ambitious develop- ment of an eco-city in the heart of the desert, near Abu Dhabi’s airport. Although scaled back in the past few years, it intends to be a zero-carbon renewable energy in- dustrial cluster with mixed use of R&D, university, com- mercial space and residencies. The master plan originally conceived by Foster and Partners called for a carless devel- opment relying on an all-electric PRT network system that would operate below street level and serve both pas- senger and freight needs. The first phase of the system is in operation (see Figure 1B) developed by 2getthere and comprises of a single loop carrying from 700 to 900 pax/ day and reaching a peak of 3600.

The prototype nature of the system meant that vehicle and infrastructure costs were comparatively high while re- liability is less than ideal. This and the rescaling of the development project are probable reasons that led Masdar City to consider more traditional alternatives. Yet the sys- tem design was shown to be generally adequate, with some modifications (primarily the inclusion of larger group rapid transit GRT vehicles) for large scale adoption (Mueller and Sgouridis 2011).

Google car
The automatic driverless car is actually driving itself in the United States. Spurred to its development by a DARPA challenge, and not strictly a PRT, it demonstrates that cur- rent technology allows automatic vehicles to negotiate normal road traffic conditions (Markoff 2010) (Figure 1C).

Concluding Thoughts: The Transition Forward
With the harnessing of abundant and deceptively cheap fossil fuels, the speed of mobility increased so much that allowed the average middle class citizen of developed countries to create personal and business networks that span hundreds and often thousands of kilometers. Mobil- ity is essentially considered a right synonymous to free- dom. As energy becomes constrained to renewable and low-carbon fluxes, mobility will remain high on our agenda. PRT systems with their promise of efficient operations can offer a valuable mobility tool.

The PRT system future likely does not lie with individual traffic-restricted applications nor with traffic-inte- grated automatic vehicles; these prototypes may help pro- pel the concept and implementation but are not likely to be viable primarily due to their cost and restricted poten- tial for scale economies for the former and regulatory nightmares for the latter. Rather, the transition will prob- ably come from the merger of the automatic car with the PRT concept at cities like London or Singapore, where the cost of private vehicle operations is already high and the desire for a low-carbon transport system is strong. An area for PRT vehicle operations can be associated with the city center. There, shared PRT vehicles could be made available to complement the public transit modes. Private cars that would like to enter the PRT-zone would be allowed to do so with the requirement to have installed (or retrofit- ted) a PRT-compatibility kit. As technology gains in reli- ability and proves its operational efficiency, the regulatory system (along with the insurance industry) will start favor- ing automatic vehicle operations over conventional driver- based systems.

It takes time and effort for a paradigm transition, but when its time comes it can be pretty rapid indeed...


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