The RUF vehicles require two separate drive trains: one for the roadway where the exterior wheels bear the load and one for the guideway where a set of interior wheels carry the load on the flange of the monorail. In addition, perpendicular wheels that clamp each side of the vertical flange of the monorail provide traction and longitudinal control. Some illustrations of these mechanisms from the website are shown below.
While lateral control is mechanical on the guideway, sensors are used for steering at switches and when entering the system. Guideway speeds of 90 mph or greater are reduced at switches to under 20 mph.
Like MegaRail, RUF anticipates that initial systems will be built to provide public transit services with automated capabilities; later, private dual mode vehicles will be allowed onto the system as demand grows. From the RUF website: "It will be impossible to start the RUF system as a system with privately owned rufs from the start. Nobody would invest in a new infrastructure without knowing if anybody would like to buy the vehicles for it. For that reason, it is the intention to start it as a Public Transport system. Since the guideway is very slender and relatively inexpensive, such a system will be less costly than traditional public transport."
Cost-Benefit: The RUF guideway is designed to carry 880 lbs. (400 kg.) per meter, somewhat less the GVW limit for MegaRail and similar to that for QwikLane. RUF public transit vehicles are essentially an attached train of private-sized vehicles that can be driven by a single lead driver. The guideway is estimated to cost $7.5 million per bi-directional mile, under $4 million per lane mile. As with all the Top Tier systems, the RUF design recognizes that limiting GVW lowers guideway costs while still providing capacity that can accommodate over 90% of typical vehicle roadway trips.
The gains RUF achieves through limited vehicle weight may be significantly offset by the scope of technology innovation required by the design. These innovations (detailed below) go far beyond mere automation and electrification, likely increasing the vehicle cost, even in mass production.
The need to slow down to under 20 mph at intersections may have negative implications for overall system capacity. It is unclear based on the reviewed materials how the RUF protocols prevent queues from forming as ever-larger numbers of vehicles enter switch zones from high-speed corridors. Limits in capacity would adversely affect the economics of the system.
Technology Innovation: Like all the Top Tier systems except QwikLane, the RUF guideway supplies electricity to power the vehicles, thereby taking on a substantial design risk, as discussed elsewhere. Also like the other electric-powered systems, the vehicles are constrained by the battery capacity to relatively limited use off the guideway.
The RUF technology innovations go far beyond mere electrification. Two entirely separate sets of wheels carry the vehicle load, depending whether it is on or off the guideway. Motors drive a third set of wheels to control longitudinal movement on the guideway; it is unclear whether these same motors or different ones draw on the battery power to drive the exterior wheels on surface streets. Such a complex combination of powertrains and power sources is unique among the Top Tier systems. Furthermore, the RUF vehicles will require sensors for lateral control comparable to those used for the other systems because the vehicles must leave the monorail in order to change direction. The reliability rate for such a complex system is unpredictable, though the likelihood of low reliability is heightened by the complexity and unproven nature of the design.
Finally, the channel in each vehicle that permits it to sit securely above the monorail splits the chassis down the middle. The lateral structural integrity provided by the typical chassis andfirewall is eliminated. The light curb side vehicle weight reduces the strength required for the vehicle frame. Still, there might be added cost to sufficiently mitigate this weakness.
Market Acceptance: The problems associated with targeting the public transit market as an entry strategy are detailed in the corresponding section for MegaRail above and they apply here as well. In sum, focusing on that 1% of the transportation sector (in terms of passenger miles) that is almost entirely publicly funded is a high-risk financial bet because the claims on those scarce funds by entrenched interests are powerful, often built into appropriations bills for years into the future.
The vehicle weight limitation of 880 lbs. is problematic. The public has favored larger, heavier cars for a host of reasons, not least of which is a greater sense of safety in the event of a collision with the many other large vehicles on today's roadways. Though recent trends in petroleum prices are steering consumers to lighter, more fuel efficient cars, the average is still around 4,000 lbs., more than four times the RUF weight. Reluctance to travel in such a light vehicle will be greatest in the early stages, when the built-out network is limited. Yet the early stage is critical to attracting sufficient numbers of users to justify expansion of the system. Thus, the low vehicle weight restriction poses a substantial risk to the potential viability of the network.
The channel in each RUF vehicle that accommodates the triangular monorail introduces a considerable visual and physical change in the established design of automobiles. Furthermore, passengers would only be able to exit easily from the side of the vehicle they entered. Public reaction is unpredictable.
Finally, the battery-limited range off the guideway reduces the utility of the vehicles. This problem is reduced to the extent an extensive network is in place to service most regional trips. However, it poses a significant impediment in the beginning, especially for the early adopters that are key to its eventual success. RUF has a design for a hybrid motor that can fit into the vehicle channel that would extend this range, though the cost is uncertain.
Status: The RUF system has been under development in Denmark for nearly 20 years. A small test track and vehicle were built in 2000. RUF has received limited funding from a number of sponsors, public and private. RUF is currently seeking a 40 million Euro private investment to bring the concept to market, tentatively with a 5 km. line in Sweden. Patents have been issued related to this concept.
