MonoMobile: MonoMobile vehicles are suspended below an I-beam like guideway, unlike the other Top Tier systems which ride above their guideways. Vehicles enter the rail at a point where it dips closer to the ground. (It is unclear from the reviewed materials how this transition is accomplished, how slow the vehicle must be traveling or what special technologies or mechanisms are employed for guideway entry.)
Electric power from the guideway drives linear motors that propel the vehicle. The motors and wheels for operation on the rail are housed on the vehicle's roof. The guideway power also recharges the vehicle's battery, which then can power the vehicle off the guideway.
The MonoMobile concept appears to specify a very light vehicle in the weight range of the PRISM or RUF (under 1,000 lbs.). The prototype is based on a three-wheel electric vehicle built in Switzerland which carries one or possibly two occupants in tandem.
Other vehicle design concepts carry up to four occupants.
In mass production these vehicles could cost under $10,000 and consume the equivalent of 80% less fuel in operation on the guideway compared to today's average automobile.
Cost-Benefit: Like the other Top Tier systems, MonoMobile limits the gross vehicle weight (GVW). This strategy has the advantage of keeping the infrastructure cost low without overly restricting the potential market of users, since over 90% of today's vehicle trips involve two or fewer occupants and limited freight. The declared cost of $11 million per bi-directional mile is high, especially given the small size of the concept vehicles and the seemingly passive nature of the guideway.
In specifying electric vehicles that can recharge on the guideway, the MonoMobile design favors fuel/emissions efficiency over vehicle size and takes on all the risks discussed previously with regard to electrification. However, MonoMobile could waive this requirement by proposing an alternative design wherein the vehicles operate with on-board power both on and off the guideway. The possible loss in fuel efficiency might be mitigated by alternative power (e.g., plug-in electric hybrids) and would reduce system risk. Moreover, existing vehicle designs may be more readily adapted to operate on the guideway, thereby broadening market appeal. (Apart from integrating the special powertrain into the roof-top of such vehicles, it is unclear what modifications would be required to the frame of today's vehicles such that they could be safely suspended from the roof under such a rail.)
Technology Innovation: As noted above, it might be possible to adapt a broad range of today's vehicles for use on the MonoMobile guideway. There appears to be nothing intrinsic to the design that requires that the vehicles be powered from the guideway's electricity; they could conceivably use their on-board engine power to drive the roof-top powertrain. The principal technology innovation is the system for propelling the vehicle on the guideway.
Like the RUF system, lateral control on the guideway is akin to that of a train on a rail, rather than the sensors used by other systems (and by RUF at switches). Like all the electrified systems, motors drive the vehicle wheels. Even if these motors are powered by the vehicles on-board engine, this still effectively requires a completely separate drivetrain for the roof-top system.
The reviewed MonoMobile materials provide only sketchy details for the roof-top drive line. Therefore the means by which the vehicle maintains ride stability, structural integrity (of the guideway, the vehicle-guideway coupling and the vehicle) and operating reliability are unclear. In contrast with the other Top Tier systems where the weight is generally born across the full vehicle width, the MonoMobile weight is born along the centerline. Little evidence was found supporting the robustness of this design against variable forces such as cross-winds or unbalanced lateral distribution of the vehicle load, especially given the proposed top speeds of 100 mph.
Switching is described as follows: "A unique switching device in the vehicle that interacts with GPS allows automatic high speed track changes without any reduction in speed." No further description or illustration was found, raising questions about reliability. The entry protocol is similarly vague: "The MonoMobile, a lightweight electric vehicle, simply drives onto the track at a point where the track dips to ground level." How does the vehicle align with the track? At what speed?
In sum, even if the intent to provide guideway electrification is set aside, there remains a host of vaguely explained and unproven technologies required to implement a MonoMobile system. Compounding the technologies compounds the risk of system problems that decrease the chances for market adoption.
Market Acceptance: As presented, the MonoMobile concept is limited to very small vehicles, requiring the market to abandon its preference for much larger vehicles in exchange for the direct benefits of fuel efficiency and congestion relief. Relying solely on this combination of market preferences is risky, especially since there are likely to be sizeable market segments with varying preference trade-offs on these two issues. The risk is compounded because at launch – where it is most essential to appeal to the broadest possible market – the utility of a MonoMobile is severely restricted until the network expands sufficiently to minimize the requirement for driving off the guideway. As noted above, it may be possible for MonoMobile to broaden the range of vehicles that can be adapted for the system by relaxing the weight restriction and abandoning guideway electrification, at least initially.
The suspension of vehicles poses a unique risk compared to the other Top Tier solutions. The public has over a century of experience of vehicles operating on top of a roadway; experience with suspended travel is exceedingly limited to conveyances like ski lifts and some amusement park rides. Assuming technology issues are resolved successfully and the MonoMobile delivers an automobile like "feel" to the riding experience, there is no guarantee that the public will become sufficiently comfortable with suspended travel quickly enough to ensure system acceptance.
Status: An electric car was modified to operate on a small prototype track section. There do not appear to be any patents related to this concept.
