Chapter 10
The Capacity of the Guideways

On highways as the speed increases the distance between cars also increases in order to provide adequate braking time.  If the car ahead should suddenly slow down, the driver behind needs some mental and muscle-reaction time before he or she can get the brake pedal pushed, and it also takes more stopping distance to brake from a higher speed.  These factors cause the capacity of a highway, in number of cars per hour, to decrease with increasing speed. 

The obverse of this is seen when traffic gets heavy; it automatically slows down a bit, the cars run much closer to each other, and the highway capacity increases.  Tests have shown that highway maximum capacity is reached at around 40 miles per hour.  But here we are speaking of highway capacity (cars per hour), not the trip time.  Trip time always increases as the speed decreases. 

         On the synchronous guideways things will be much more favorable.  There braking can never occur and spacing between cars can be close and constant, therefore the higher the chosen operating-speed the more vehicles per hour the system will handle; and the shorter the trip times become.  In mathematical terms, the capacity of the guideways will be directly proportional to the velocity divided by the car spacing (the sum of the average length of the vehicles and the distance between them). 

         There is much pressure on us these days to leave our cars at home and use the buses or light-rail systems.  Let us assume that people listen, and transit use doubles.  “Wonderful, twice as many people are leaving their cars at home and our traffic problems are solved.”  Not by a traffic-jammed mile!  On average, about two percent of the travelers are now transit riders.  In this example there are now twice as many, or four percent, leaving their cars off the highways.  That means the percentage of people driving their cars went from 98% all the way down to 96%.  That would do next to nothing toward solving our transportation problems.  Do the planners ever look at the arithmetic?  Later in this chapter it will be shown that conventional transit systems couldn’t carry anywhere near the traffic now being carried by our cars, even if there were ample rail tracks and dedicated lanes for buses. 

In defense of the planners, up until now they have had little choice.  Those responsible for transportation have spent a lot of time and money proposing everything they could think of that might reduce our transportation problems.  Even if they knew it wouldn’t work they had to propose something, anything, to reduce the public outcry over lack of action.  Currently there is nothing that would do the job.  A National Dualmode Transportation System can do the job, but most regrettably we won’t have it soon enough to avoid considerable chaos. 

A hundred years ago most rural folks got water into their houses by carrying it in buckets from a well, creek, river, or lake.  Those old buckets delivered very little water compared to modern plumbing, since a pipe can provide continuous flow and a bucket can’t.  The same observation applies to transportation—buses and trains are intermittent: They are like one-at-a-time buckets.  Automobiles run or “flow” continuously on the highways fairly well.  Dualmode cars on the guideways will flow even better, at much higher flow rates. 

The large clearances we leave between cars on the highways are necessary because of the unsynchronized traffic, the limitations of human drivers, and the limits of automobile braking and tire traction.  And since we can’t increase the speed safely with human drivers, the only way to get more highway capacity is to add more lanes.  But more lanes bring more pains. 

In contrast, dualmode-guideway capacity will be remarkably high because in addition to high constant guideway speeds we can run the vehicles very close together.  With synchronization, hardly any space between cars will be needed on the guideways. 

Fortunately the technology required for safe very close spacing is already largely available.  Mentioning just one such development: In 2000, Peter Mattila, Director of Business Development for MagneMotion, wrote, “For fixed guideway transport systems, to achieve top performance it is critical to be able to run vehicles with very short headway [car spacing].  The magnetic guidance and switching technology [LSM] that MagneMotion has developed allows this capability.”  Preliminary studies show that about one foot minimum clearance between cars will be plenty in the REV system, therefore the following capacity comparisons will be based upon that figure. 

Assume the traffic on a very busy highway lane is traveling at an average speed of 60 mph, and the time clearance between cars averages the “two seconds minimum” recommended by many State Patrols.  Also assume the average length of the vehicles is 15 feet, and there is an average of 1.2 passengers per car.  This works out to 27.64 cars per mile and 1,990 passengers per hour for each highway lane. 

For comparison: Assume the cars on a 60mph guideway are also 15 feet long and carrying 1.2 passengers each, but there is only one-foot clearance between cars.  Then there will be 330 cars per mile, 19,800 cars per hour, and 23,760 passengers per hour.  Dividing, we see that one guideway lane would carry almost as much as twelve highway lanes. 

The California Department of Transportation figures that the maximum capacity of a highway occurs at about 45 miles per hour and about 2,000 cars/hour/lane.  Using those slightly different numbers one 60-mph guideway lane would carry the equivalent of ten highway lanes. 

Again using the California assumptions, a 200-mph guideway lane at full capacity would be the equivalent of thirty-three highway lanes.  

          I assumed an average of 1.2 persons per car (but I wonder what two tenths of a person looks like).  The actual number of occupants per car seems to be even less than 1.2, at least in this area.  But what if, in an emergency, we carry an average of six persons per car on a single lane of 200mph guideway?  Its capacity would be 396,000 people per hour.  Theoretically we could evacuate a city of over a third million people in less than an hour using only one dualmode guideway lane.  This we could call high-speed high-volume continuous-flow.  Emergency-evacuation planners, please take note.

The capacities of bus, train, and airline systems depend upon the number of vehicles dispatched per day or per hour, and upon the number of passengers per vehicle.  Note that the system capacity is independent of the speed of the vehicles in these “by-the-bucket-full” dispatches.  It would be impossible to carry a major percentage of our present highway traffic on any of these systems since the frequency of the departures and arrivals required could not be met.  It would take nearly one fully loaded standard forty-seven-passenger Greyhound™ bus every minute to allow the elimination of one highway lane full of automobiles.  And it would take an astonishing 1,685 Greyhound buses per hour (28 buses every minute) to equal the capacity of one 200-mph dualmode guideway!  Oh yes, and we should note that all of the twenty eight 47-passenger buses per minute would have to be completely full, but the cars on the single-lane guideway could do the same job carrying an average of only 1.2 persons each. 

With railroads or “light rail” one and a third trains per minute carrying a thousand passengers each would be required to equal the 66,000 cars-per-hour carrying capacity of one guideway at 200 mph.  All of these trains or buses couldn’t possibly be unloaded and reloaded every minute, unless many acres of parallel tracks and lanes were provided at each station.  And many many acres for auto parking would be required at each station. 

If we are in a hurry and the trip is long we now usually fly, but many airports are already operating at capacity—our traffic congestion is not limited to the highways.  The good news is that one 200-mph guideway will have the capacity of three fully loaded Boeing 747-400 jumbo jets per minute.  Try that on any airport. 

         On the guideways it will take only four hours to “drive” between two cities 800 miles apart.  Because of their capacity, speed, low use-fees, and door-to-door service, the cross-country dualmode guideways will greatly reduce domestic airline travel. 

When we include the time to make reservations, the travel time to and from the airports, the parking, ticketing, waiting, the stressful security checks, baggage handling, delayed flights, and cancelled flights; the total time from home to final destination will surely average less by guideway than by jet for trips up to a thousand miles or more.  In the Gasoline Alley comic strip Skeezix had it right when he observed, “Now we can get there in far less time than it takes to drive to the airport and get checked in.” 

         Guideway travel will be much cheaper than flying, we will have our own cars to use at our destinations, and let’s not forget comfort, safety, and privacy.  Does a crying baby or an obsessive talker in the next seat make for a peaceful flight? 

         Who needs all of the hassles of flying if we can get to our destinations faster and cheaper by taking our own cars all the way?  And who needs the problems from weather, airline strikes, airport expansion; and the residential noise, air pollution, and fuel consumption of jets?  A Confession: This heresy is coming from an airplane lover and former private pilot after a 40-year engineering-management career in the aerospace business.  He predicts that Boeing will someday be building dualmode systems—and a lot fewer airplanes. 

When the guideways are completed, with one lane in each direction, everything will be rosy for many years; the traffic on the guideways will be light, and there will be few delays or frustrations. 

But assume that the population continues to increase and the standard of living continues to allow most of us to drive cars (dualmode cars).  When the traffic finally begins to approach the guideway capacity in some dense areas it will be time to add a second guideway lane there.  Note that adding a second guideway lane doubles the guideway capacity, but adding another lane to a five-lane highway adds only a fifth more capacity.  Expanding the guideways will therefore be many times cheaper than continually expanding the highways, as we now do.

On the guideways, if there were a shortage of exit ramps some cars wishing to exit would be forced to continue on to the next exit.  If this happened often the paying customers affected would demand and rapidly get more exits installed there.  With an automatic guideway-use-fee system, the forces of supply and demand will provide timely expansion of the guideways much faster and more efficiently than do the complex forces that control our “free” but bureaucratic highway system. 

         On the highways if there is insufficient exit-ramp capacity at some location the exit ramp plus the right lane of the highway jams up.  If too many cars squeeze onto the highway, all of the traffic slows down, sometimes way down.  We also see this phenomenon when an airport is operating at capacity: The jets line up awaiting their turn to use the takeoff runway, or they stack up in a holding pattern awaiting permission to land.  The same delays occur in bus systems and railways when they are crowded.

Note here a very significant advantage that crowded REV guideways will have over crowded trains, airports, and highways: When any of the existing systems are running at or near capacity the system as a whole slows down and all of the riders and drivers are delayed.  But the REV guideways will continue to operate at full synchronous speed clear up to and including full capacity.  The only people who may be delayed are the few people who can’t get onto a guideway because it is full, or those who have to take a later exit ramp, because of insufficient ramp capacity at some places at some times.  The trip-time for the vast majority of guideway travelers will be as fast during rush hours as during slack-traffic periods. 

                                Next: CHAPTER 11
                    Getting onto and off of the Guideways

                                Back to: CONTENTS

Last modified: August 01, 2006