The Pocket Traffic Accident Reconstruction Guide, Seventh Edition

Back in the mid-90s, after I wrote some articles for LAW and ORDER magazine, Officer Timothy Staab of the Glendora, California Police Department in Los Angeles County contacted me. Tim was preparing to take the ACTAR (Accreditation Commission for Traffic Accident Reconstruction) exam and wanted to brush-up on some equations. In that effort, he put together a pocket-size book of formulas, which he sent to me for review. His book measured 3.5 by 4.75 (9cm by 12cm) and fit nicely in a shirt pocket. Tim titled it The Pocket Traffic Accident Reconstruction Guide: A Complete Traffic Accident Reference Handbook, and published it himself. The 56-page paperback enabled accident investigators (that was in olden times when crashes were called accidents) to have handy at collision scenes rather than trying to recall dozens of equations from memory. Many formulas (slide-to-stop, radius, combined speed) are reasonably simple and thus easy to remember, but some (weight shift, percent grade into degrees, motorcycle speed from wheelbase reduction) are trickier. In addition to containing most of the equations accident reconstructionists will ever need, it contains a comprehensive glossary. As of this writing, over 2,500 of the pocket handbooks have been sold. Officer Staabnow Lieutenant Staab in charge of his agencys investigations bureau, plus he is a member of the California Association of Accident Reconstruction Specialistsincluded one of those disclaimers that warned the author assumes no responsibility for the accidental or intentional misuse, improper application or typographic [sic] errors of any equation" and so on. Along came Lawyers & Judges Publishing Company and convinced Staab to authorize them to publish his book. Although their latest edition has four fewer pages than the original, it contains more material. L&J's version supplements some drag factor/post-impact data and adds a few helpful accident reconstruction Websites. They even made it easier to read by changing to a more legible font. They added to some of the glossary definitions. While the books dimensions are a few millimeters larger, it should still fit in most shirt pockets.

What's 56 pages long, 3 X 5 inches big, is less than a quarter-inch thick, fits in your shirt pocket and costs only seven bucks? Timothy Staab's The Pocket Traffic Accident Reconstruction Guide, The Complete Traffic Accident Reference Handbook. Tim said he wrote the book so he could have a set of crib notes when he took the ACTAR test. He didn't know it's an open book exam. Most of us can remember the slide-to-stop formula and we can compute critical speed in one fell swoop with our hand-held calculators. But every now and then, certain equations escape us. Was that "(v2/'oo) or "(v/'oo)2" ? Then there's the dreaded delta-V, the change in speed using conservation of linear momentum. Or that formula for determining Principal Direction of Force. Not many have that one committed to memory. Staab's little handbook is just the thing for officers at an accident scene. He suggests that the guide fits well in a posse box. For those who don't have the foggiest idea what a posse box is (I didn't when I first heard the term), it's one of those aluminum clipboards with a flip-lid and space in the back to store report forms, a dime novel, or a very flat peanut butter and jelly sandwich. The book doesn't contain that long formula for figuring the energy consumed in a crash (and hence a speed) where you make all those crush measurements, but does include some rule-of-thumb equations for small, average, and large cars when they get smashed, and the one to use when a cycle's wheelbase gets reduced from t-boning the side of a car or an old oak tree. There are also some vehicle braking percentages to use when working an crash involving large buses, heavy trucks, and tractor-semitrailers. There's even a conversion table in case you need to convert miles into kilometers, knots into feet per second, or Newton-meters into foot-pounds. Some of you may have tried to use one of those not-so-well publicized horrendous weight-shift equations, the necessary values for which are almost always unobtainable. Staab has a simple one but it only applies to a two-axle vehicle. There are some quick 'n easy equations to use for impact speed when a vehicle hits a rigid pole. Keep in mind that the equations are no better than the accuracy of the input data and that the answers are subject to interpretation. That is, all vehicles won't react or crush the same in a given accident, but at least the answers should put you in the ballpark.