A study to determine the effectiveness of five breakaway lighting standard base designs in reducing the severity of vehicular impacts by means of full scale dynamic tests is reported. Ten head-on tests were conducted utilizing identical 1966 sedans weighing 4,540 ilbs. And impacting 30 ft. Lighting standards mounted on the various frangible or slip-base designs. All of the poles used in the tests were steel with the exception of one tapered aluminum design. The impact tests were conducted as follows: (1) three 40 mph tests on a 6-in. High cast aluminum insert base, one on the basic design and two on modified versions, (2) three tests on a notched bolt insert base design, two at 40 mph and one at 15 mph, (3) two tests on a multi-directional steel slip base design developed by the texas transportation institute, one at 40 mph and one at 15 mph, (4) one 15 mph test on a 20-in.high aluminum transformer base, and (5) one 40 mph test on a formed aluminum pole fitted and epoxy cemented to an 18-in. High cast aluminum sleeve type base. All base designs tested broke away with a significant reduction of impact resistance as compared to rigid base designs as shown by tests of others when impacted at moderate speeds (+ 40 mph). The texas slip and the notched bolt base designs offered the least impact resistance of the designs tested at this speed. However, when the impact speed was reduced to 15 mph with the notched bolt alternate, test results showed a marked increase in the impact severity, apparently due to approaching a static loading condition. A similar reaction was experienced in a 15 mph test on a 20-in. High aluminum- transformer base. Although a 40 mph test was not conducted on a transformer base in this study, tests by others and operational experience had previously demonstrated its effectiveness in this speed range. The impact resistance of the multi-directional slip base design was essentially the same when impacted at both 40 and 15 mph. These findings supplement and substantiate those of the texas transportation institute in that this design is one of the most effective devices for the reduction of the severity of vehicle impacts into lighting standards at all speeds and angles. (Author/publisher)
Samenvatting