Electric Motorways?

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 Responses to Electric Motorways?

  1. R A Fontes
    March 4, 2012 at 4:16 pm Link

    This is two years old and would have greater transmission losses, but could be cheaper, safer, and subject to less wear and tear.


  2. Joseph E
    March 4, 2012 at 6:37 pm Link

    If you are willing to go to the trouble of rebuilding roads and buying new trucks, why not instead spend the money on electrifying freight railroads and investing in multi-modal shipping?

    BNSF already runs many trains where truck trailers are directly loaded onto freight rail cars. With investment in electrification, double-tracking (or triple-tracking in some places) and more multimodal transfer points, freight could still move fast and reliably while being totally electric. This wouldn’t require ripping up and rebuilding highways while inventing a totally new transportation technology, and it can be done with private investment.

    Raise the tax on diesel, start instituting higher fees for trucks to use highways and roads, provide an freight rail infrastructure bank if necessary to provide financing, and the free market will do the rest.

  3. billb
    March 5, 2012 at 9:30 am Link

    Yea , I gotta go with Joseph. The train system is there in-place already , waiting for an e-upgrade. It is fully distributed , which makes it great for feed-in power from massive remote solar and wind arrays.

  4. EngineerScotty
    March 5, 2012 at 9:55 am Link

    Just to be clear, I’m not suggesting we go out and build such a thing–it may have been thoroughly researched and discarded. And I’m all for improving the rail network, particularly for signal upgrades and the like. I do think it useful to occasionally peer outside the box.

    One big obstacle/issue with the current freight network, particularly the Class I lines, is the focus on long trains. While efficient for the railroad to run, it can be a big problem for shippers. Even if one DOES have a containerful of stuff on a truck, which can be driven to a depot somewhere and then loaded onto a train, assembly of trains is a time-consuming (and energy-intensive) effort, likewise for breaking tham down on the other end. For some types of cargo this is OK, for others it is not.

    Also, when you have long trains dominating the traffic, it becomes inefficient to add short trains into the mix–this is a big reason the freights generally hate passenger rail on their tracks. There are signalling enhancements to overcome this, but some significant regulatory reform would be required. (The FRA doesn’t appear to be interested in such).

    Rail transport of freight has several significant advantanges over trucks. Among them:

    * Lower friction between ground and wheels, resulting in lower energy costs
    * Right of way at crossing, requiring minimal stopping over a journey; also resulting in lower energy costs.
    * While this doesn’t apply much in the US (at least not to freight), trains (and other guided vehicles) can be powered by route-supplied electricity.
    * Low labor costs per ton–a two-man crew can safely operate a mile-long (or more) train; whereas hauling the same amount of cargo by truck would involve hundreds of drivers.

    However, to realize many of those advantages, you have to have a lot of freight to haul, and a lot of time to haul it. This is a big reason so much freight nonetheless moves by truck.

    It does seem to be that there might be a useful ground-based shipping mode somewhere between traditional trucking and traditional rail.

  5. Steve B
    March 7, 2012 at 10:47 pm Link

    Electric trolley buses are also nice and quiet!

  6. Wells
    March 9, 2012 at 11:45 am Link

    If this is the same Jerry Schneider who champions Personal Rapid Transit nonsense, then I’m reminded how some people propose one bad idea after another. Seattle is where the worst engineers go to become professionally obstructionist to sensible engineering.

  7. EngineerScotty
    March 9, 2012 at 12:01 pm Link

    It is that Jerry Schneider. My reference to his site does not, of course, imply endorsement of his broader platform of ideas.

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