Revised August 18, 2004
McCrary Personal Transport System
The McCrary Personal Transport System (PTS) is a simple, inexpensive step beyond present transportation methods, using small, private vehicles resembling conventional automobiles for both street travel and rapid, intermediate distance commuting. The PTS roadway multiplies by several times the capacity of a single lane of traffic by using a light weight, mass produced, prefabricated steel structure and existing rights of way with minimal interference to existing infrastructure. On the roadway the vehicles are integrated into an automated, constant velocity traffic stream but operate as standard automobiles on city streets and roads. Actualization of a PTS system faces no speculative technical problems and hence, could be achieved in a reasonably short time. A consortium of industrial companies is the recommended organizational structure to undertake this project.
Homer T. McCrary - 310 Swanton Road, Davenport, CA 95017 - (831) 457-5025
1.0 THE PERSONAL TRANSPORTATION PROBLEM
One of the most costly, stressful inefficiencies of modern living is that of travel between home and workplace. In most cities two alternatives, automobiles and mass transit are available, each with near prohibitive problems. For example:
Freeways cannot solve the city and inter-city traffic problem.
In many locations with mass transit, the system makes a minimal impact on the traffic problem. People prefer private cars.
- People want the schedule flexibility of private cars.
- People want door-to-door transportation.
- People don't like having to change trains, busses etc. to get to their destination.
- People don't like waiting at bus stops, train stations or street corners for their ride.
- Mass transportation systems are usually slower than private cars due to frequent stops and transfers.
- People like to travel privately or with company of their own choosing.
- Private cars are usually more physically comfortable than mass transit travel
- People avoid mass transit because of fear of crime, exposure to contagious diseases and unwlecome personal encounters
2.0 THE PTS SOLUTION TO THE PERSONAL TRANSPORTATION PROBLEM
The McCrary Personal Transport System (PTS) can move large numbers of people for intermediate distances, 20 to 200 miles, with speed, efficiency, safety, privacy and comfort and then provide a seamless transition to conventional street driving. Operating in the rapid transit mode at its design specifications (100 feet/second (68 mph) and bumper-to-bumper vehicle spacing) a single lane PTS can accommodate 20,000 or more vehicles per hour. By comparison, a single lane of a conventional freeway is reported by traffic experts to accommodate maximum of 2,000 vehicles per hour. This is confirmed by actual counts of peak traffic on California State Highway 17 between San Jose, CA and Santa Cruz, CA (at the Saratoga summit) measuring a four lane total peak throughput of 7,100 cars per hour or 1775 vehicles per hour per lane.
Description of the PTS
The PTS uses small, specially equipped, private vehicles resembling conventional automobiles for both street transportation and for high-speed longer distance trips on the PTS roadway. For city driving they are street legal private cars with standard controls. For longer distances they become part of a constant speed stream of automated vehicles on an inexpensive, prefabricated, lightweight, steel, roadway, that is usually built as an elevated structure above existing roads and freeways.
Thus, a commuter leaves his home in his own vehicle, drives in a normal manner under manual control over city streets to a nearby roadway check in station. The master computer then communicates with the onboard controller and, upon confirmation that the vehicle is authorized and roadway-ready, commands it to accelerate under onboard automatic control, up an onramp to the precise roadway speed of 100 feet/second and enter a vacant vehicle sized "cell" in the stream of vehicles. The constant speed, close spacing of vehicles results in a throughput of many times the number of vehicles per hour than conventional freeway.
While entering, exiting and traveling on the roadway, all vehicles are monitored and directed by the master computer. The onboard control system serves a function similar to that of an aircraft autopilot, maintaining constant vehicle speed, and proper heading on the roadway, precise vehicle to vehicle spacing and precise control for entry and exit with no human control or intervention.
PTS Traffic management protocol
The roadway traffic control model simulates a chain of virtual cells (each of which can accommodate one vehicle) moving at a constant speed of 100 ft. / sec. along the roadway. The master computer is cognizant of the location and status of each cell and initiates a vehicle's acceleration run so that it converges with an empty cell at the correct time and velocity to join the traffic flow. Since speed and vehicle separation are controlled with high precision by the onboard controller, very little clearance is needed between vehicles. No other traffic is inconvenienced by the entering vehicle as it converges into an empty cell at zero relative speed with respect to nearby vehicles.
3.0 THE PRIMARY PTS SUBSYSTEMS
The primary PTS sub-systems, the roadway, the vehicle, the onboard sensing and control system and the master computer and the communication link are briefly described below.
Description of the Roadway
The roadway is erected over the rights of way of existing freeways, roads and streets. By using standardized, prefabricated, 60 foot long road sections supported on pre-installed, standard columns, a simple mechanized erection process (setting each new section from previously laid sections) requires a fraction of the time and cost of normal freeway construction and does not disrupt traffic in the road below.
Since all vehicles using the roadway will have identical wheel spacing and follow a single traffic path within very close tolerance, a full roadbed is not necessary. Two rectangular tubular tracks support the vehicle wheels and a mesh net fills the void between the tracks. The tracks can be given a rough, hard surface of tungsten carbide or some other such material to minimize wear and provide traction.
The steel curbs bounding the roadway serve two purposes. They can physically guide the vehicle wheels in the unlikely event of a control system failure, and they provide the lateral position reference for the vehicle guidance system to keep the vehicle centered on the tracks or guide it to an off ramp.
The primary structural member of the roadway is a 4-foot diameter steel tube that provides strong rigid support, a conduit for utilities and a means for maintenance personnel access along the roadway.
With the vehicles always at a single constant speed, the turns are banked for precisely coordinated maneuvers (that is, with the gravity vector vertical in vehicle coordinates). This permits smaller turn radii without passenger discomfort and by eliminating lateral forces, skids and tire wear are minimized.
Description of the Personal Vehicle
The PTS vehicles are similar to conventional, street-legal rubber tired, small automobiles and are compatible with the production technology of most automobile manufacturing companies. Conventional controls provide for street driving and an onboard automatic control system directed by a master computer that takes control while on the PTS roadway. Most cosmetic and proprietary design features are discretionary to the particular automobile manufacturer; however, all PTS vehicles must meet specific compatibility requirements in order to be accepted by the PTS system.
Description of the onboard sensing and control system
The vehicle sensing and control system consists of direction and speed actuators, a suite of onboard position, velocity and direction sensors, an onboard controller and a two way data link to the master traffic management computer.
Continuous sensing of fuel supply, battery charge, engine and bearing temperatures, tire pressure, oil pressure, engine vibration, exhaust chemistry and other indicators of potential problems will inform the onboard controller of a potential failure in time to remove the vehicle from the roadway. Using the data from these instruments, the onboard controller also reports vehicle readiness to the master computer prior to the vehicle's entering the onramp. Entry will be refused if any potential malfunction is reported.
Functions of the central computer
The central computer performs a few, very important tasks, however, for reliability and convenience, these functions are kept to a bare minimum. When on the roadway, the vehicle acceleration, guidance, speed control, safety, and emergency response functions are performed by the vehicle's onboard control system. The central computer controls the traffic protocol, keeping track of the location of open cells so that it can initiate the vehicle's acceleration run. It collects data for billing purposes and other housekeeping functions. It has no function, other than communication, when a vehicle is under manual control on streets and highways.
A communication link, provides two way data exchange between the master computer and each vehicle. A cell type radio link is a possible choice but optical, direct microwave and other methods must be comparatively evaluated. Even though it must communicate with any or all vehicles on the roadway, the amount of data traffic is minimal since most operational functions are performed by the vehicle's onboard systems.
4.0 SYSTEM RELIABILITY AND SAFETY
Safety is inherentin the PTS concept and embodiment. High speed, bumper to bumper driving is normally viewed as hazardous with manually controlled vehicles on conventional roads and freeways since a vehicle may maneuver, brake or falter in less time than the following driver's response time. The close spacing and constant speed of the PTS preclude a high relative velocity between vehicles and a resultant serious collision.
In addition to the safety inherent in the PTS concept, all components of the PTS, are designed for the specific mission with reliability and safety as first priority and component redundancy where performance is vulnerable. Preliminary analysis indicates that it can achieve a level of safety far superior to that of the best conventional freeway.
The time is right for the development of the PTS. The need is acute, and all of the system and subsystem technology, production methods and management techniques are mature and available. In some congested cities, failure to respond to the need will increasingly cripple the economy and diminish the quality of urban life. In many congested cities, freeways can no longer be expanded or new freeways afforded.
A PTS installation will cost a fraction of the price of new or expanded freeways and can utilize existing rights of way, minimizing the impact on existing infrastructure and the need for major government funding.
We believe that a consortium of companies encompassing the necessary skills and technologies (automotive design and manufacture, guidance and control, steel fabrication and erection, communication, marketing etc.) could develop and operate a PTS in a very short time - years, not decades. Operating the PTS as a toll system will amortize the investment and yield profit to the investors.
The system described herein is covered by patent applications filed by Homer T. McCrary. This discussion is a revision of McCrary's paper of 1/23/99, revised 8/19/99. All of the descriptions, concepts and inventions originated with Mr. McCrary and remain his sole property. As of April 20, 2004, five patents covering the PTS have been granted. R.O.B.