Novel Transportation Modes-Existing Conditions

The project research team reviewed literature reviews, along with the submissions received following the RFI, to better understand basic characteristics of novel transportation systems. USDOT staff also provided input based on their knowledge of additional concepts and research in progress. The review is necessarily somewhat limited based on the project scope outlined earlier in this publication. As noted previously, the research team did not consider maritime or aviation concepts, nor many current trends considered to be novel modes (e.g., ride sourcing through a mobile application) because of their use of existing technologies and systems. An overview of the surface transportation novel mode concepts that the researchers reviewed is outlined in the following section, together with a brief discussion of some of the factors impacting potential viability.

Major Modal Types Identified

Proposed systems may not fit exclusively into one typology and may share elements of two or more.

Personal Rapid Transit and Automated Transit Network Systems

There are many variations on the theme of small, automated, public-transportation vehicles that provide on-demand service for individuals or small groups. Personal rapid transit (PRT) and automated transit network (ATN) systems typically involve fixed guideways, yet have the flexibility to provide point-to-point service within this framework. The introduction of PRT and ATN systems as a general concept is not new, for example, the Morgantown, WV, PRT system began service in 1975 and the Ultra PRT system opened at Heathrow Airport in the United Kingdom in 2011. Each novel mode concept that the research team reviewed in this project typically offers a refinement to the idea, such as lower costs or improved system control. Although there are a few existing examples of commercial PRT systems, these are generally very limited in scale, and the overall concept is not yet in widespread deployment. The research team therefore included PRT and ATN within the scope of the research, especially with respect to future innovations relating to the concept. PRT and ATN systems offer the prospect of combining the flexibility and convenience of personal vehicles with the energy savings and other efficiencies of mass transit; however, it is unclear whether such systems can feasibly scale up to serve high passenger loads without reverting to something more like conventional fixed-route transit. In addition, although PRT and ATN systems are sometimes described as a potential means of addressing the “last-mile” problem of conventional transit services, they too operate on fixed guideways and can face last-mile problems of their own—particularly in the context of low-density settlement patterns in most metropolitan areas. 

Platooning and Quasi-Rail Systems

Platooning concepts involve automated operation of conventional automobiles or newly developed vehicle types in platoons that would reduce travel times, fuel consumption, and labor costs. In some applications, they use a fixed-guideway system. Platooning concepts require advanced safety systems to ensure that vehicles can travel at very close headways and, in some cases, also require the development of a fixed guideway and specialized vehicles. The close spacing is designed to improve throughput and speeds, while also improving fuel economy through reduced aerodynamic drag. One key challenge for the commercialization of these systems is that similar technologies (e.g., cooperative adaptive cruise control) are currently in development for conventional automobiles. These systems could provide many of the benefits of platooning without the need for developing an alternative modal system.

Hybrid Mode Concepts

Hybrid mode systems combine the functionality of two different transportation modes. In theory, this allows users to take advantage of the benefits of both modes. For example, a hybrid highway–rail vehicle could take advantage of the flexibility of highway travel and the fuel economy of rail transportation. A specific example of a hybrid mode that is progressing toward commercialization is the concept of a “roadable aircraft,” such as the aircraft developed by Terrafugia. The on-road capabilities of this aircraft allow it to use the regular road system to cover the distance between the airport and the traveler’s ultimate origin and destination, thus removing much of the inconvenience of changing modes. The infrastructure needed to implement these types of approaches often includes interchange stations or facilities and potentially more significant infrastructure when the second mode is not in common use already. In addition, significant vehicle design changes would be required for many systems. The need to operate safely in two different modal environments may require design compromises that increase cost, add weight, or reduce fuel economy. Such systems can also face development challenges because of regulatory issues related to the demands of meeting two different, and potentially conflicting, sets of safety and emissions rules.

Tube Transportation

Tube transportation refers to a set of concepts for very high-speed intercity travel using capsule-like vehicles propelled through tubes that have been fully or partially evacuated to reduce aerodynamic resistance. Entrepreneur Elon Musk’s Hyperloop concept, proposed for implementation in California, is a high-profile example. There are other examples of this approach, and multiple competing concepts exist for the specifics of vehicle design, propulsion, and operation. Tube transportation is a surface concept, but its high speeds of potentially 1,300 km/h (800 mi/h) and its limited, long-distance route corridors would likely make it more of a natural comparison to aviation than to automobiles and transit systems. The technology for this concept is still under development, and its cost-effectiveness is not known. The very high speeds also present challenges for right-of-way alignment and passenger comfort while the low-oxygen environment of the tube could require robust emergency protocols and onboard life-support systems.

Infrastructure-Based Vehicle Charging

Mobile recharging of EVs would address some of the key limitations of market penetration and foster greater use of vehicles with no tailpipe emissions. These concepts comprise various forms of recharging for vehicles while traveling on the roadway, usually through contact or near contact with a new form of dedicated infrastructure. A variety of systems have reached the prototype or demonstration phase, but the cost-effectiveness and commercial viability of more widespread deployments has not yet been shown. These systems also generally do not address the limitations of automobile travel, in particular, congestion, high vehicle ownership costs, and limited options for non-drivers.

Powered Exoskeleton

Powered exoskeletons are wearable suits that use motors to provide additional power to the wearer’s limbs, thereby increasing strength and improving endurance. Several prototypes have been designed for use in military and other settings and for people with mobility impairments. At least one product is in commercial use overseas. If commercialized more broadly for the general public, these kinds of suits would reduce exertion and fatigue on walking trips and could expand the distance that travelers are willing to walk to destinations and other travel modes. In turn this could increase the role for pedestrian trips and mitigate the last-mile problem associated with fixed guideway transit. Reaching this level of consumer acceptance would likely require significant advances in cost, weight, and ease of use. More familiar technologies to augment human power, such as electric-assist bicycles, may provide similar benefits in terms of increasing the radius of non-motorized trips.

Personal Mobility Vehicles

Personal mobility vehicle is an umbrella term for a variety of low-speed, single-passenger motorized vehicles that may travel on sidewalks, public roads, and in some cases, within buildings and elevators. Seated and standing prototypes have been tested in Japan, where the primary intended market is the rapidly aging population. Some vehicles are piloted by the user and others have self-driving capabilities. These vehicles can greatly expand the mobility options of those who have physical difficulties with driving and walking. Unlike the current generation of mobility scooters, many of these vehicles are intended to have both in-building and on-road capabilities, which raises an additional series of engineering and safety challenges.

Self-Driving Electric Shuttles

Self-driving electric shuttles are low-speed, fully automated (driverless) EVs that can serve as multi-passenger shuttles and on-demand personal transport within a defined area. They are typically envisioned for controlled environments, such as campuses and military bases, or for urban areas with little or no vehicle traffic. There is a range of vehicle types and sizes, ranging from small pods to minibusses. Active field operational tests are underway in the United States and Europe, including the U.S. Army’s Autonomous Robotics for Installation and Base Operations series of pilot programs and the European CityMobil2 program. For campuses and certain other environments, the self-driving electric shuttle concept offers some of the advantages of PRT and ATN systems with additional flexibility to add or modify services without the challenges of developing an entirely new fixed-guideway infrastructure. Further advances in sensor systems are needed before widespread adoption can be expected.

Shared Fleet of On-Demand Self-Driving Vehicles

A shared fleet of on-demand, self-driving vehicles is a novel mode primarily in its business model and operational concept, rather than in the vehicles themselves or the highway infrastructure. It is possible that some upgrades may be needed to enable fully automated operation (e.g., improved pavement markings and onboard sensing). The concept, which has been articulated in various forms in research publications, is predicated on replacing the current paradigm of personal automobile ownership with the idea of “mobility as a service.” Mobility would be provided by a shared fleet of self-driving taxis that could be summoned on-demand by using mobile technology. Compared with conventional taxicabs, this concept envisions shorter wait times and greater availability through centrally coordinated fleet optimization, as well as the ability to offer significantly lower fares because of reduced labor costs. Because cars currently spend most of their time parked, this approach would allow personal mobility needs to be met with a much smaller vehicle fleet, yielding economic and environmental benefits. The approach could also incorporate changes to vehicle propulsion, such as electrification, particularly because the fleet approach could yield economies of scale with the necessary fueling infrastructure. At the same time, some simulations have shown that this approach can actually increase overall vehicle–miles traveled, and therefore also emissions because of the repositioning movements of empty vehicles between trips. The wait times can also grow significantly during times of peak demand. This concept would require significant cultural change to implement, as most motorists are accustomed to having their cars immediately available and commonly leave personal items in the vehicle between trips.

Summary

A brief summary of the major modal concept types considered by the project research team is shown in table 2.

Table 2

Observations

All of the proposed novel modes are unique in some way; however, several of them have attributes in common. These shared attributes are summarized in the following section.

Motor Vehicle-Based Systems

The majority of concepts reviewed by the research team focus on a motor vehicle, but a few concepts propose a new cycling or pedestrian infrastructure. There were relatively few operator-powered transportation concepts.

Heavy Infrastructure Demands

Several of the concepts envision an extensive and entirely new infrastructure that may be elevated, at grade level, or sub surface. These systems must provide a corresponding large level of benefit to justify their cost and impact on an already crowded built environment. Examples of these systems include evacuated tube transportation systems, variations on maglev technology, and some PRT and ATN systems.

Automation

Several of the concepts that the research team reviewed seek to minimize human labor. This is typically to reduce labor costs, address human factors issues, improve safety, and expand operational capabilities.

Diversity in Deployment Scale and Scope

There are large variations in the degree to which the novel modes are intended to disrupt the current transportation marketplace. Some are small scale or niche products that are intended only for certain environments (e.g., institutional campuses or central business districts). Other concepts envision more widespread use but with a strong focus on serving only certain types of trips (e.g., long-distance travel). A few concepts envision that the novel mode will lead to the near-total replacement of current road and rail networks.

Outlook

Many of the reviewed concepts are in an early stage of development, which means it is not possible to meaningfully evaluate their potential. The project team identified the following features as highly relevant to the potential of many of the concepts to be adopted.

Changing Transportation Landscape

Many of the concepts reviewed by the research team are motivated by long-standing transportation issues, such as highway congestion and vehicle emissions; however, the transportation landscape is changing. Changes in vehicle automation, wireless technologies, improved materials and batteries, and vehicle ownership models could increase the safety, convenience, and fuel efficiency of the existing transportation system to the point where they diminish the business case for many novel modal concepts.

Automation

The concept of automation promises to improve roadway operations without requiring massive additional infrastructure investment of changes in travel behavior. Market-ready automation of automobiles and transit vehicles could make the development of other modes unnecessary or less cost-effective. For example, many of the concepts reviewed in this project are based on the idea of on-demand fixed-guideway service; however, a fleet of on-demand automated vehicles could provide on-demand service to a wider service area, without the associated costs of maintaining a dedicated guideway.

Vehicle Sharing

As vehicle-sharing options become more familiar over time, and as more businesses and transportation infrastructure caters to them, the increased usage of such services may result in reduced personal vehicle ownership and changes in mode choice associated with vehicle-sharing options. This could encourage the adoption of a novel mode that supports car-sharing services. Car sharing might also be a mechanism for addressing last–mile issues with many transit-oriented modes. It is also possible that car sharing may provide the ease of automobile usage without the need for ownership and may reduce transit usage for some parts of the population. This may be dependent on the segment of the population in which the greatest car-sharing growth occurs.

Electric Vehicles

The combination of wireless and inductive charging opportunities; improved batteries that enable more efficient, environmentally-friendly energy storage; and lightweight vehicles made from innovative composites is likely to drive improvements in EV range, cost, and environmental profiles. This kind of development would tend to diminish the value proposition for some of the proposed novel modes that are predicated largely on saving energy through new modes or infrastructure. A counterpoint here is that existing strains on the national electric grid may need to be resolved before EVs can be fully implemented, even with improvements in battery storage. A flexible grid in which one can provide power to the grid or draw from it would be ideal.

Federal Infrastructure Funding

Federal infrastructure funding from the Highway Trust Fund has been reduced, and competing budgetary obligations (e.g., military and social security) have also reduced funding in this area. This is particularly significant for concepts that require large-scale changes in infrastructure.

Opportunities

There may be opportunities for novel modes to complement the transportation innovations that are being “pushed” by these technological shifts. Ongoing developments in vehicle automation could provide enabling technologies or synergies for novel modes that are based on automated operation. In addition, complementary approaches to addressing last-mile issues, such as car- and bicycle-sharing schemes, may facilitate the deployment of transit-oriented novel mode approaches. Such complementarity may be an important contributor to the success of novel mode implementation in coming decades.

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