Corrosion eating away at traffic light poles

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In July 2017, a traffic light pole at the intersection of Fifth and Sixth avenues in Downtown Pittsburgh crashed to the ground. Investigators said the reason was the bottom of the pole had rusted out.

Pittsburgh has 622 traffic lights, and Target 11 went around the city and found some in better conditions than others.

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A spokesperson for the city said they are working on upgrading 156 of the light poles. Pittsburgh also has 44,000 street lights, which the city spokesperson said, "Through our street lighting contract, we have a general assessment of street light fixture condition and an obligation to maintain it in a good state of repair."

PennDOT's District 11, which oversees Allegheny, Beaver, and Lawrence counties, has replaced five light poles over the last several years due to poor conditions.

"We are looking for corrosion, any cracking in the welds, or the nuts and the bolts," said Chris Ciesa, a PennDOT engineer.
 

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Target 11 went with PennDOT engineers who were inspecting a steel structure on the Parkway West near Pittsburgh International Airport. 

PennDOT inspects sign structures every two to six years, and light poles every three years, using specialized tools including one called a "D-Meter." That allows engineers to see how much remaining steel is still in place, and whether there's any corrosion.

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Assistant professor of materials science and engineering at Carnegie Mellon University, and said failing poles is a classic example of problems with infrastructure. He said galvanized steel poles can last more than a century, or less than 25 years, depending on the conditions they're in. In Western Pennsylvania, the lifespan of the poles may be shorter because of the harsh weather conditions, and the road salt used in the winter.

"Salt is sodium chloride, and chlorides are very bad for corrosion resistance," Webler said. "It gets covered in some salt, it gets rained on over some period of time, and that's what's causing the corrosion that eventually leads to that failure."

Target 11 repeatedly asked the City of Pittsburgh if they have an inspection program, but the city has not responded.


 

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