University of Washington researcher Jerry Schneider points to a Swedish company (Elways) researching the concept of “electric motorways”–highways equipped with electric lines which can be used to energize and power vehicles traveling thereon. Elways proposed architecture consists of buried third-rail power, accessed by lowering a pickup shoe into a channel embedded in the road surface; to increase safety, the system also energizes those portions of the rail that are presently serving vehicles. It is anticipated that vehicles using such roads will be capable of disconnected travel, either from a battery or an internal combustion engine (certain maneuvers such as lane-changes will require disconnecting from one lane’s power rail and connecting in another lane).
Using current technology, the speed limit for overhead powered road vehicles appears to be about 70kM/h (40MPH). Unlike electric trains that have fixed guideways and only one overhead connection needed (the rails provide the ground return path); trolleypole systems need to accomodate horizontal maneuvering of the vehicle (both within-lane and lane changes) and the bouncier suspensions needed to accomodate potholes and other defects/obstructions in the road surface; and the non-conductivity of rubber tires means a second wire is needed for the return path. Ground-level third rail, commonly found in grade-separated metro systems, is generally considered unacceptable for public roads due to the obvious safety hazard the third rail poses to pedestrians.
Right now, the major application of overhead-powered electric road vehicles is the trolleybus. The speed limit isn’t a problem for many urban transit applications, the greater maneuverability of a trolleybus over a mixed-traffic streetcar is generally considered an asset, the lack of diesel pollution is also considered a major advantage, and electric trolleybusses have noted advantages on routes with steep grades (it’s no accident that two of the North American cities which extensively use them are Seattle and San Francisco). However, trolleybusses are noted to have reliability issues, many object to the wiring, and as such, most transit companies in the US have abandoned them. (See this article for a discussion of the merits of the electric trolleybus in Portland).
Use of overhead caternary to power trucking (particularly long-haul trucking) though, seems to not be an attractive solution.
That said–rather than try to retrofit existing mixed-traffic highways with electrical sources, perhaps an alternate solution is in order? Places such as Adelaide, Australia and Cambridgeshire, UK have built guided busways–essentially dedicated BRT lines where the bus is physically guided down the busway, permitting it to achieve faster speeds and a somewhat more comfortable ride in a narrower footprint. This gives some of the technical advantages of rail, coupled with the greater flexibility of a bus–the busses can leave the guideway and maneuver in mixed traffic as appropriate. (Note that neither of these systems are powered–diesel vehicles, operating under their own power at all times, are used).
What if such a solution were build to handle trucks? A guided truckway, which kept vehicles traveling in fixed channel, could make the electrical interface needed to use well-known solutions like overhead caternary much more tractable and capable of higher speed, particularly if the guideway could also be used for return current. The truckway road surface could be optimized for heavy vehicles, reducing the amount of damage incurred by road surfaces elsewhere (heavy vehicles such as trucks and busses cause the vast majority of road wear). A guided truckway could permit either electric-powered or diesel-powered operation (i.e. diesel-powered trucks could use the mechanical coupling only), and driverless operation while in the guideway would be a more tractable problem with a fixed guideway. Unlike rail or water freight, which requires cargo to be maneuvered from truck to train/ship (a process made easier by containerization, though still expensive), guided trucks could use the local streets to pick up a load and drive to the truckway, use the truckway for the long-haul part of a journey, and then return to the local streets for the last mile on the other end–in this way, they would fill a niche between unguided trucking and rail.
Long haul bus service could also use guided truckways, especially in shorter corridors where HSR is not cost-effective.
This falls short of Elways’ vision of a motorway where all the vehicles, including personal automobiles, are running on roadway-supplied electric power. But many of the problems involved are more tractable when limited to larger vehicles operated by professional drivers (or automated control systems).7 Comments