Date of this Version
MwRSF Research Report No. TRP-03-223-09
The New York State Department of Transportation (NYSDOT) mounts pedestrian “hand/man” signals to aluminum
poles and uses frangible transformer bases to allow the system to break away. However, engineers at NYSDOT believed that the material properties of the aluminum poles themselves would allow the pedestrian signal poles to break away without the use of transformer bases. Elimination of the frangible transformer base would result in significant savings.
An aluminum pedestrian signal pole system was erected at the Valmont testing facility and tested with the Valmont- MwRSF/UNL pendulum with crushable nose in accordance with NCHRP Report No. 350 test designation no. 3-60. Upon impact the pole broke away from the base plate assembly, and the surrogate vehicle change in velocity was measured to be 13.9 ft/s (4.2 m/s), satisfying the limit of 16.4 ft/s (5.0 m/s). However, the remaining stub height measured 4.5 in. (114 mm), and violated the 4 in. (100 mm). Thus, the test was deemed unsuccessful. The results from the impact test were used in a numerical analysis to predict the change in velocity for the high-speed impact test, test designation no. 3-61. This analysis showed that the aluminum pedestrian signal pole would also satisfy the occupant risk criteria during a high-speed test.
Since the pole cleanly broke away in the test and the high-speed impact analysis showed a satisfactory change in velocity, the excessive stub height was the only result that prevented this installation from becoming crashworthy. As such, three separate design modifications were presented for aiding the system to satisfy the stub maximum height limit.