Traffic Safety

Auto repairman to customer: "I couldn't repair your brakes, so I made your horn louder".

requent and quick physical communications are of such vital importance to modern society, that we accept a considerable number of accidents every day. And the number of people who die in traffic accidents are steadily climbing, although not at the same pace as the traffic grows. Road traffic is the most common way of travelling, and, as can be seen from the diagram below, by far the most deaths in the Western World occur on the roads. 3 things are noticeable from the diagram: Pedestrians seem to live more dangerously than people travelling in motorcars. But the diagram gives the wrong impression here. The mileage covered by pedestrians per unit time cannot be even remotely compared to the mileage covered by motor vehicles.

Private aircraft have a considerably higher death toll than commercial aircraft. Train accidents (at least in Sweden) cause a lot more casualties amongst those that happen to be on the spot, than amongst those that are travelling on the train involved. From that, one can conclude that railway cars are quite good at protecting their passengers when the accident does occur. Accidents in traffic The "Brickwall Stop" requirement Measures to protect beamcar passengers Evacuation of passengers from the beamcars.

The Dilemma of the Road Traffic he road traffic philosophy has painted itself into a corner. It is a curious fact, especially in the affluent "developed" world, that a lot of resorces have been devoted to making motorcars faster, and their engines stronger. At the same time, considerable efforts have been devoted to restricting travel speeds everywhere, for safety reasons, and especially in built-up areas. And considerable expense is being devoted to enforcing those speed restrictions. Drivers are daily caught in speed traps and fined. Sometimes, they lose their driver´s licenses. Likewise; considerable efforts and expenses have been devoted to building good roads for fast travelling. And, after a while, it has been found necessary to devote more money to construct speed bumps and obstacles of various kinds in the streets, often paid for directly by local residents, with the purpose of slowing down vehicle speeds. The idea of motorcars and good roads is to quickly get from point A to point B. But these effort are also being hindered at great expense and causing irritation in the process. The end purpose is of course to bring down the rate of traffic accidents. And the prevailing attitude is always that you want fast roads through other neighborhoods in order to quickly get to your own neighborhood. But you certainly do not want a highway in front of your house! Certainly, one could find a better (and considerably cheaper!) way of solving this dilemma?

The "Better Way" In the beam-carried traffic system, as in all traffic systems, there are safety aspects to consider. The beam-carried traffic system does not contain any opposing or intersecting traffic and there are no unprotected people milling about along the traffic routes. The road- and railbound traffic is now developing in the same direction (with for instance multi-level intersections, protection arrangements between lanes with opposing traffic and prohibited passage for unprotected travelers along the highways). But the costs for all these measures are extremely high. This is especially true when it comes to urban areas.

One safety risk that remains in all these traffic systems (also in the beam-carried traffc) is the danger of having your vehicle hit from behind by another vehicle. There is an awful lot of neck injuries caused by this type of accidents alone! As it turns out, it is the concern for the travelers' safety that puts the actual limits to how short the travel time and how high the transport capacity will be. In these respects, however, the uatomatically controlled beam traffic system turns out to be a formidable traffic machine, which - with considerably higher degree of safety than road and rail traffic, at all weather conditions, - provides larger traffic flows and shorter travel times than all competing transport systems. Just imagine the quite common situation of a line of road vehicles (i.e. private cars, trucks and buses), travelling along a road. Imagine that the weather is bad, with limited vision and maybe ice on the pavement. Suddenly, the caravan hits upon a stationary line of vehicles. Will the drivers have time to react before tearing into the stationary cars? This is a question of: distance of vision, time to react, distance between vehicles, their speeds and braking conditions. When road conditions are good the ability to brake is determined by the travelers' protection (such as safety belts). History is full of examples where hundreds of road vehicles coming behind each other have driven into stationary vehicles, resulting in widespread personal injuries and damages to vehicles. The indirect reason is, as a rule, sudden slippery roads and/or fog banks that reduces visibility.

Not all drivers realize how far their car travels during the time it takes the driver to react to something. If a person steps out in front of a bus, for instance, it takes the driver about 1 second to react and to move his foot to the brake pedal.	If the car is travelling 50 kilometers/hour (or about 31 miles/hour) and is at the rear of the bus, the driver won´t even have started braking before the person in the street is run over. And a bus is 12 meters in length (about 40 feet).

The situation is not really much better for railroads and streetcars. Imagine for instance a railway train, with mechanically coupled cars in a long row, where the engineer suddenly discovers a truck stranded squarely across the rails. The long train with low-friction steel wheels has no chance of stopping in time. In urban areas considerably more unprotected pedestrians and bikers than motorists are being killed. Street violence which is regularly reported by the media, claims "only" about a fourth of all people being killed in traffic accidents.	The beam-carried automatically driven vehicles will discover obstacles within microseconds, and commence braking within milliseconds, with a decelleration suited to the safety of the passengers. All passengers would be required to be seated, as they are in for instance the buses of London. Safety belts and swivelling of the seats so that the passengers would travel backwards could be applied when deemed necessary for safety (i.e. at peak traffic hours and at high cruising speeds). There is also the interesting idea shown in figure 1:5 below, of fastening the seats in the ceiling of the cabin, and let them swing forward-upward by their own volition when the vehicle is emergency braking.	The number series "1 1 3 3 5 5" is quite interesting. Note how the un-even digits "1 3 5" have been doubled; i.e. we write every digit twice. Now, if we split this into two groups, and divide the second group with the first, we get: 355 / 113 = 3.1415929 wich is the value of Pi, with an accuracy of eight decimals, using input values having only three digits accuracy. This peculiarity was discovered by the Chinese mathematician Tsu Chung-Chih about A.D. 480. This is quite startling, considering that there are no secret mathematical connections leading up to this result. This is not the way you would normally calculate the value of Pi, since Pi is the relationship between a circle´s circumferens (S) and its radius (r), and also between a circle´s area (A) and its radius, expressed as: S = 2 * Pi * r A = Pi * r2. No doubt Archimedes would have found this interesting.
Figure 1:5

2. The "Brickwall Stop" Requirement

Figure 2:1

On the page titled A Formidable Traffic Machine! we present and explain these 2 formulas; 1: T = D/v 2: D = v * r + (v2)/(2 * a) + (v * a)/(2 * j) + L Where: v = speed (meters per second) a = acceleration or retardation (meter / s2) r = reaction time = 0.15 seconds (for a computerized system such as this, the reaction time is considerably shorter than for a human motorist) L = the length of the car in meters D = distance in meters between the center of two cars (see figure 2:2) T = distance in seconds between two cars j = jerk (m/s3) at retardation, i.e. how the rate of retardation changes over time. This is a so-called comfort factor, whose calculation has to be experimentally arrived at. Figure 2:2 The safety distance to the car up ahead is dimensioned for a hypothetical "Brickwall Stop", which means that if the car ahead (nr. 1) should stop dead (as shown in figure 2:1, it should be possible for the next car (car nr. 2) to stop in time. It might be thought unnecessary to keep this distance between all cars, since cars nr. 3 and thereafter would have more time to stop, as illustrated in the time diagram in figure 2:3 below. But there is a delay, indicated by T1, that makes it necessary to keep this requirement.

There are various delay factors that makes the total time to bring the car to a halt slightly longer than the actual braking time. How long these factors are in duration is largerly a design matter. But typically, the total time for these delays should be shorter for cars 3 and after, than for car 2, because car 3 (and those cars that might follow behind on the same beam segment) doesn´t have to perform radar detection and perform its own decisionmaking. It is simply ordered by the node to stop! Refering to figure 2:3, we have: A: Radar sweep time B: Processing of information C: Car 2 takes the decision to brake; and information dispatched to node D: Mechanical delays, brakes are activated E: Car 2 is braking F: Information processed in node G: Order to brake is dispatched by the node to cars 3 and after H: Received order is processed by car 3 I: Car 3 takes the decision to brake J: Mechanical delays, brakes are activated K: Car 3 is braking. Figure 2:3 In figure 2:3, the braking times has been depicted as equally long (i.e. E = K). Normally, car 3 should not have to brake as hard as car 1, but the delay T1 could be a worrisome factor here. This delay would depend on how busy the node computer is, and whether indeed it is functioning properly. If T1 grows too big, the radar of car 3 would detect car 2 braking and go into action and emergency-brake car 3, following the same procedure as car 2. So there is never any danger of collision.

When it comes to automatic beam transport there is, however, an inherent conflict between efficient use of the beams and keeping safe distances between beam vehicles. Of the three schemes deemed most suitable for PRT, none is founded on inherently safe operation (i.e. “brick-wall” stopping criteria). While the deceleration rate could be set to infinity, the resulting spacings between cars are usually considered excessive for efficient operation. Since motorists routinely violate brick-wall following distances, it would be difficult for automated systems to improve capacities without doing the same. More parallel beams would be needed to enhance capacity along a route. Passenger protection at impact velocities of up to 15m/s can be assured by letting the passenger cabins have substantial energy absorbing front structures and (maybe) a hard padded dash close to the passenger. Passenger protection at impacts around 30m/s is however impossible to obtain with any reasonable combination of shock absorbers and passenger protection devices."	Adding shock-absorbing "crumple zones" at both ends of passenger cabins is no problem, since the vehicle cabins have to be aerodynamically formed, anyhow. With elongated noses at both ends of the cabin, as in the bottom version on the figure at right, containing shock-absorbing material, the brickwall criteria would not need to be adhered to when traffic capacity is strained, as might be the case at rush-hour. The two "noses" would not then "count" when considering the length of the vehicle (for safety distance calculation purposes). The vehicle at bottom right would be considered as having the same length as the vehicle in the middle.

Definition of "Reaction time" The first term in the equation above represents the reaction time. In an automatically controlled system such as this, the reaction time is not only a property of the vehicle, but of the whole system involved in causing the beamcar to brake. Thus:

The vehicle could be commanded to stop, which would involve the time for the computer involved to make the decision, for the communications system to transmit the signal, and for the car to act upon it. The vehicle could receive an alert from the beamcar ahead, in case of a mishap with that car. Then we would have to take into account the time it takes to generate the signal, as well as to transmit and receive it.

The vehicle could detect an object with its obstacle detection device. This would in all probability consist of a "ladar" which scans an area at a certain distans in front of the beamcar. This scan has to be repeated a few times and evaluated by a computer. Since there is sweep time involved, the reaction time would be of the order of 0.15 seconds or thereabouts, and this is probably the longest of these three alternative causes for braking.

There would be no opposing traffic. There would be no crossing traffic. There would be no unprotected people along the travel route who can get injured or cause damages. Snow, ice and water cannot get access to vital parts of the guideway or the cars. No animals or stormfelled trees along the traffic route. Several sensors and microprocessors along the beams keep track of absolute and relative positions and speeds as well as acceleration och retardation for all vehicles. Safetybelts are available for travelers for all vehicles that at any time are likely to exceed an emergency braking retardation of 0.2 g (g = earth's acceleration at sea level).

Electronic "shock absorbers" between the propulsion cars inside the beams. Radar beams would extend far enough along the beams so that the carriages underneath would not have to take direct hits if cars should come too close to each other. Thus, no damages to the passenger cabins at a collision. There would also be sensors at regular intervals and at strategic places inside the beams to keep check on the cars. The length of the radar field would be limited by the beams´ curvature sideways and up/downwards. Multiple sets in all cars of equipment essential for safety (such as fire extinguishers and ladders). "Predictive maintenance": Built-in testing equipment in the cars enabling the car's computer to keep itself informed about the condition of components that are subject to stress and wear. Things that can thus be measured are overheating and undue vibrations. If something of a suspicious nature is detected, the car would (if necessary) order a new transport for the passengers, hand them over at a suitable meeting place to the new vehicle, and proceed, if possible, to nearest repair depot. This is called predictive maintenance, a more intelligent way of keeping beamcars in good shape than the customary preventive maintenance. Preventive maintenance relies solely on MTBF (= Mean Time Between Failures), which is based on failure statistics. In order to, at an early stage, detect possible faults in the beams, maintenance vehicles would travel along the beams during nighttime, measuring uneven guideways and detecting any failures in the supply of power or data communication to the nodes and vehicles. A quick repair of any such detected faults along the beams, using repair vehicles that would enable the repair crew to even replace beam segments and poles that cannot be fixed in time for next day's traffic. Immediate re-routing of all affected traffic, if any kind of obstacle appears along the beams. It is thus vital that practically all places along the beam network can be reached from at least two directions. Single one-way beams over long distances should generally be avoided. Using stops at close intervals from each other along "berthing beams" parallel to the thru-traffic beams, instead of big, expensive stations at long distances from each other. This makes it easier to get a faulty vehicle off the main beam and onto a side track. Uninterruptible power supplies which at short notice can step in and keep the traffic running, should the normal power supply fail. An electrical battery in each vehicle, with enough capacity to at least take the vehicle to the nearest berthing place. The vehicle behind a faulty vehicle can sometimes push the faulty one to the nearest berthing place and maybe to a repair station, using the propulsion cars' shock absorbers, mentioned above. SwedeTrack´s "FlyWay®" system, with lifts on vehicle cabins, makes it possible to lower the passenger cabin to the ground using the elevator, provided the car is equipped with one. Otherwise there would be a ladder aboard. This would save the passengers, if the car cannot in any way be moved. Exhaustive testings and measurements to arrive at components that would provide long MTBF:s (see above). A high level of preparedness to fix faults and keep the traffic flowing. A modular and standardized concept in building the system would aim at quickly replacing faulty modules instead of repairing them on the spot. Considering the high degree of automation and use of cheap components and replacement parts that characterize the Beam System, this would be economically feasible.

Figure 3:2 Figure 3:3; Suspended traffic systems have a considerably better safety record than ordinary train service Figure 3:4 Figure 3:5 Figure 3:6; FlyWay´s beamcars can lower their cabins to the ground for evacuation, using the lifts

4. Evacuation of Passengers from the Beamcars

here might be occasions where passengers need to be evacuated from the beam vehicles, on the spot where the vehicle happens to be. Such situations would be: A vehicle is stranded on a beam segment that has been damaged in such a way that the vehicle can neither move forwards or backwards A vehicle has broken down in such a way that it cannot move or be towed/pushed by another vehicle to the nearest station An emergency, such as fire, necessitates immediate evacuation

In such situations, the carriage would be lowered to the ground be means of the elevator. Should the elevator be out of order, it should be possible to lower the carriage manually, in a controlled manner, using the force of gravity. If the carriage does not reach the ground, the function for steadying the car would be automatically activated, whereupon a fire-engine or similar vehicle on the ground could reach the car with its ladder.

If the car, for some reason, cannot be lowered far enough to stretch the elevator, this steadying function would not be activated automatically. A possible solution would be for this function to be activated manually from the carriage or by remote control. A bigger problem is that the carriage might be hanging over terrain that cannot be reached by a rescue vehicle on the ground. For such situations it would be a good idea if the carriage could be evacuated by way of its front or back end, into another beam vehicle. If none of these options work, one could always use a helicopter with a ladder.