A Least-Cost, Least Disruptive Dualmode Concept
by Larry Howe
In discussing dual-mode, the things that are NOT in a proposed design are probably more important than the things that ARE in the design. What I mean is, a design which departs as little as possible from the current most favored mode (the private automobile) is likely to be more popular with the public, and therefore gain faster and wider acceptance. It seems to me that dual-mode can be achieved at very little cost and disruption of the current transportation system, at least in comparison with some of the alternatives.
My proposal is as follows, and please forgive the parts of my proposal that are either obvious or infeasible, since I am fairly new to this debate. This system consists of privately owned automobiles that are identical to current ones, except they have four added pneumatic tires, one on each corner, which are designed to run along the interior walls of a guideway(1). These wheels have a light-duty suspension system to accomodate minor irregularities in the guideway. This may take the form of a simple compressed air spring, which has the added benefit that these wheels can be retracted when not in use(2)(3).
The guideway is simply two concrete walls, a fixed distance apart. They are similar to existing median barriers ("Jersey walls"), except that they may have to be somewhat smoother (i.e. not jointed), depending on the capabilities of the vehicles.
Let's consider for a moment that this is the entire proposal: A concrete guideway, and standard passenger cars with lateral wheels. What do we get from this?
1. An extra travel lane at the cost of two concrete walls and six feet of width. If the highway is such that this width can be subtracted from existing lanes and/or shoulders, then you get an extra lane with no new pavement. If this six feet must come out of the existing travel lanes, then you can get two lanes in the width of one. These two new lanes could be traveling in the same, or opposite directions (or the direction can be switched between morning and evening, as many express lanes are today).
2. Increased safety. Elimination of accidents caused by lane changing. Any collisions that do occur will be linear, where seat belts and air bags are most effective. Rollovers will be almost impossible.
Now let's add to this a collision avoidance system that keeps a controlled distance between vehicles, and also allows vehicles to travel at high speed in platoons.
3. Even greater traffic capacity, with some estimates at 5 times greater (on top of the doubling of capacity due to a six foot lane width).
4. Even greater safety.
Admittedly, this is future, but I include it for completeness. If and when Phases I and II were successful, this could be expanded futher to again double transportation capacity, by designing a 3 foot wide vehicle and guideway. We all know that the single occupant vehicle gives the ultimate in flexibility and convenience. Rather than fighting this trend, it can be fairly easily accomodated with a guideway. The vehicle would consist of 3 a foot wide car with one rear powered wheel and one front steering wheel. It would have a complete weatherproof body and a standard automobile seating arrangement except, of course, it would have only one front and one rear seat. It would have a light-duty pneumatic wheel at each corner, mounted on a 1.5 foot long extension arm. When not in a guideway, these arms will pivot down to bring the light-duty wheels in contact with the pavement and provide needed stability for such a narrow vehicle. When in a guideway, these arms will pivot upwards and become the wheels which ride on the vertical walls of the guideway to guide the vehicle.
5. Another doubling of capacity (we are up to 20 times current capacity now).
6. No reduction in mobility nor convenience, compared to current vehicles.
And let's look at what we have NOT had to develop to get this far:
1. Any kind of new vehicle propulsion system.
2. Dedicated right-of-way.
3. Any kind of expensive guideway system.
4. Any kind of public expenditure on rolling stock.
5. A collision avoidance system that detects and avoids hazards from either side.
6. An automatic steering system. (The automatic controls that we would need (braking and acceleration) already exist today, in the form of ABS and cruise control, and could be adapted to fully automatic acceleration and braking.)
The various rationale I have for this system are:
1. People like to own their own cars. From a practical standpoint, the convenience is unbeatable. There are also many intangibles. People don't like mass transit because of the close proximity to strangers. People may stare at you, harass you, or worse. People tend to leave trash and messes behind. Then you have to hire janitors to keep the vehicles clean. When people own the rolling stock, then the government doesn't have to raise taxes to buy it, and also people can keep their vehicles as clean or as dirty as they like. It will be a lot easier to get people to spend several thousand dollars each to purchase AND MAINTAIN a guideway-compatible car, than it would be to get a combination of government agencies to raise and spend the money to purchase AND MAINTAIN an equivalent amount of rolling stock.
2. Seemingly minor technology changes can be insurmountable. Take the battery powered car as an example. Doesn't sound like it's insurmountable, I mean we flew to the moon, right? And yet California forced auto companies to waste tens of millions of dollars trying to make a usable battery powered car, then quietly repealed the legislation when it turned out no one could do it. In the meantime, Honda and Toyota designed hybrid cars which are a lot like a standard car, except they use an electric motor sparingly in specific situations where it does a better job than a gasoline engine. That's why I think the vehicle and guideway should be as much like current technology as possible.
Larry Howe firstname.lastname@example.org 21December2002
(1) A similar vehicle, which exists today, are the trucks used for railway maintenance. These are standard light trucks which have added a rail axle on the front and rear, which axles can swing up and down. When the truck is on a road, the axles are up. At any grade crossing, the truck can drive onto the rails, lower the axles, then proceed down the rail line.
(2) Many dump trucks have a similar setup. They have a fourth axle, just ahead of the two rear axles, which is raised when the truck is empty, but is lowered by air pressure to become active when the truck is loaded.
(3) These extra axles could be mounted much the same way that towing hitches are mounted today. Many cars are not manufactured with a hitch, but do have a hard mounting point where a hitch can be attached. A mount that can support a hitch pulling a several thousand pound load is easily strong enough to support the lateral forces of a guideway. Larger vehicles such as trucks and SUVs have mount points at the front for e.g. snow plows, tow hooks, etc. However, my belief is that most passenger cars today do not provide a hard mount point at the front of the vehicle, so this minor design modification would have to be made before this system is feasible.
Last modified: January 04, 2003