**Lesson #3:
Reaction times**

Just hit the brakes quicker! How?The answer is to use today's high speed computers, sensing systems and control systems to yield automatic and much faster reaction times. Humans typically are expected to use up about 3/4 of a second to react to an emergency and start hitting the brakes. The computers used in modern sensing and control systems can easily cut that decision/reaction time by a factor of 10 to .075 second.

Typical Human Reaction TimesRemember your last Department of Motor Vehicles written test? They usually have one multiple question on stopping distances. They gave you a speed and you had to pick which of the four distances shown would represent the actual automobile stopping distance. I never bothered to memorize those answers because a long time ago I just worked it out backwards mathematically. Whenever I encountered this question again, I just cranked out the simple math. The California DMV formula for stopping distances used to assume it would take the average driver 3/4 of a second at speed just to react to an impending emergency and get one's foot stomping on the brake pedal (reaction time). Then hitting the brakes hard, the driver will be able to get stopped (decelerate) at a steady maximum of 1/2 g. Simple as that. For some reason the DMV has increased the reaction time to 2.5 seconds and the same 1/2 braking deceleration. They may be worried that people are paying attention less than ever. This yields the following results:

Initial SpeedReaction

DistanceDeceleration DistanceTotal Stopping Distance35 mph128.3 feet 81.7 feet 210 feet*45 mph 165.0 feet 135.2 feet 300 feet 55 mph201.6 feet 201.9 feet 403 feet*65 mph 238.3 feet 282.1 feet 520 feet 75 mph 274.9 feet 375.6 feet 650 feet 80 mph 293.3 feet 427.3 feet 720 feet 90 mph 329.9 feet 540.8 feet 870 feet 100 mph 366.6 feet 667.7 feet. 1034 feet *1999 officially recognized DMV reaction plus deceleration distances are given at: DMV Automobile traffic is not that tightly packed because

than computers do. Most, not all, drivers follow other cars with a spacing that they are comfortable with. Normal drivers do not relish focusing their entire concentration to follow right on someone's tail for minutes or hours on end. Without any mathematical formulas, whatsoever, we all figure out how close we can followhumans need more reaction timesand still get safely stoppedif something weird happens just in front of us. We know the vehicle in front of us CANNOT instantly STOP! We adjust our spacing mentally by simply including a factor for the distance the other driver would take to stop once we see his brake lights appear. (You may have read about a section of a San Diego, California freeway that is currently being used to test automatic computer driven automobiles. The cars travel at 65 MPH autonomously - while spaced just feet apart from each other. The benefit in tightly packing traffic ismore people per lane per hour, which means less congestion, and the elimination of building more $24 million per mile freeways to carry the ever growing traffic.)

Public Transportation Braking Laws

Public transportation, such as trains, on the other hand, have to follow unreasonable braking laws which have nothing to do with the reality of physics. Trainscannotlegally follow each other any closer than the distance required to make acomplete stop. This is analogous to you having to be completely stoppedby the pointalong the freeway where the driver in front of youtapped his brake lights. We all know this point has nothing to do with where you could possibly ever contact his car. His car cannot stop instantaneously! We all have learned to sense from assorted little cues whether or not the driver in front of us is paying reasonable attention or off in la la land (tough to check by looking directly into their eyes). Years of driving experience allow us totrustthat the person in front will hit the brakes and gradually slow down and not just go piling stupidly into a stalled truck or whatever.

What do these train laws have to do with SkyTran?

Mainly, itgot us thinkingabout just what would it take tostill followthat train braking law andkeepour high density 1/2 second spacing! If you are traveling at 100 MPH, you are covering 146.7 feet each second.Another SkyTran could be 73.3 feet in front of you (one half second ahead).Guess what,we can take great advantageof ourSkyTranMagLev drive unitbeing trappedinside the hollow, roll formed, monorail track. What if we include a hydraulic brake (for emergency use only) that could squeeze against a rib that we also roll formed into the track (it runs the entire length of the track)? Then, no longer isemergency braking deceleration limited by the traction capabilities of rubber tires on asphalt or concrete!!!

Superior braking has tremendous safety implications!

If we assume we can let the on-board radar computer take 75 iterations to detect, confirm and apply this hydraulic brakes (75 milliseconds = .075 second) and we further control the hydraulic squeeze pressure to give us awe can get fully stopped in a mere 55.6 more feet. Including the 11.1 feet used up while the computer is making up its mind, the total distance is 67 feet. This actuallyconstant 6 "g" deceleration,meetsthe train braking law requirement -WOW!Modern factory automation has forced the development of very fast sensing and control systems. Click

to read about Siemens factory visual inspection system that checks 32 different dimensions of a product and decides to accept or reject each part - at the rate of 1,600 parts per minute (one part every 4/100 of a second)!HERE