Dual-mode Vehicle - Dual-mode Solution

Dual-mode Solution

Dual-mode vehicles address the problem of providing two different types of service in a single vehicle: a low-speed short-distance vehicle for typical trips, and a high-speed long-distance vehicle for longer trips. They do this by tuning their performance for the short-distance portion, the easy problem, using electric motors for traction and batteries for power. The vehicle can be made more efficient because it will only be operating at low speeds; crash protection needs are reduced, and suspension loads are much lower. The result is a vehicle similar to the Neighborhood Electric Vehicles that have appeared in the 2000s.

For longer distances, custom routes are used. For car-like vehicles these generally look like U-shaped concrete roadways. These routes, or "guideways", also supply power, eliminating the need to use the batteries and allowing the motors to run at much higher power settings. Generally the systems also use this power to recharge the batteries while en route, so the vehicle will be fully charged when it reaches the end of the guideway. Since the guideway is tuned for serving vehicles of known size and weight, the capital costs are similar to those of conventional expressways.

The canonical example of a car-like dual-mode vehicle is the Alden staRRcar. The staRRcar looked like existing city cars of the era, using a steel chassis with fibreglass bodywork on top. Batteries gave the vehicle a 30 mph top speed with a range of a few tens of miles. For longer distance trips, Alden envisioned concrete guideways similar to the existing interstate highways. When the staRRcar entered the guideway, small wheels on either side of the vehicle pressed against the sides of the guideways and handled steering, while an on-board guidance system prevented collisions with the vehicle in front - the only collision hazard in this mode of transit. Since the driving was automated, the vehicles could be operated with almost no distance between them, or "short headways, which increased the capacity of the lanes. A single lane of guideway could safely operate at loads twice or greater than a conventional expressway.

Dual-mode cars have never been installed operationally, but the same system has seen some use as the basis for guided bus systems worldwide. These systems do not necessarily provide power as well as guidance, using conventionally powered buses. Experiments with hybrid systems on trams as a way of recovering power otherwise lost in braking (about 25% of the load) led to the concept of using supercapacitors in place of batteries because they could handle the large currents being generated. This led to the idea of removing the overhead electric feeds for portions of the tramways, using the hybrid to power the tram through these gaps - this allowed the often messy cable runs over road intersections to be removed, improving aesthetics. The two types of vehicle have recently converged in the form of the rubber wheeled tram, which uses tram-like overhead power and a single road-embedded rail as a guideway, a few of which allow the vehicle to leave the guiderail and operate as a traditional electric bus.