Author(s):
N.J. Rowan, E. Kanaki
Publication Date
December 1967
Abstract
The severity of collisions with luminaire supports on Texas highways prompted the Texas Highway Department to initiate a study with the Texas Transportation Institute dealing with the impact behavior of such supports. The object of the study was to determine the impact characteristics of various pole and base mounting designs now in use on Texas highways. In addition to the "state of the art" study, development was initiated on a slip base design for break-away luminaire supports. The "state of the art" study consisted of conducting full-scale crash tests of various luminaire support designs. The tests indicated that steel poles mounted on steel transformer bases produced the most severe collision. Flange-mounted steel and aluminum poles were next in the hierarchy of collision severity. Support poles mounted on bases that exhibited a brittle fracture under impact loads (cast aluminum transformer bases and inserts) produced the safest collision. The studies also pointed out that low speed impacts frequently produce secondary collisions when the pole strikes the top of the vehicle when it falls. However, these collisions are far less severe than collisions with fixed-base supports. A slip base for luminaire supports was developed which exhibited multi-directional break-away properties. Laboratory studies were conducted to determine the optimum base design. The results of the study were validated by two full-scale crash tests. These tests indicated that the base performed as anticipated and appears to be a satisfactory device for safer luminaire supports. As a result of this research, the Texas Highway Department has adopted the cast aluminum transformer base as a design standard for new lighting systems to be constructed under their jurisdiction. Several other states apparently have followed. Also, at least on state is using the multi-directional slip base design. On the basis of this research, the Texas Highway Department has installed cast aluminum inserts under some 300 steel transformer bases already in place. Several accidents have involved these inserts and the results have been very favorable. There have been no fatalities, and the few injuries have been due to overturning on steep slopes or striking other fixed objects after collision with the luminaire supports.
Report Number:
75-8
Link(s):
Document/Product
http://tti.tamu.edu/documents/75-8.pdf
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