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City maintains streets with lasers

CARLSBAD — The city of Carlsbad recently used lasers for road analysis to stay one step ahead in its street maintenance efforts. It gained a foothold in using new software technology to pinpoint and address potential trouble spots.
“This was the first time the city used the laser-camera array to collect cracking, rutting, and roughness data,” said Jon Schauble P.E., associate engineer for the transportation department of the city of Carlsbad.  “The previous city-wide pavement condition assessment occurred in 2001 prior to the availability of this technology — at that time, all the pavement distress data was collected by trained technicians doing windshield surveys.”
According to the city of Carlsbad, it has roughly 330 centerline miles of public roads. And in its 2010 Public Opinion Survey, street maintenance and repair topped the list as the second most popular answer in how the city could improve the “quality of life” for its residents.
In 2010, the city contracted Infrastructure Management Services (IMS) to complete a citywide pavement evaluation.
“To complete this assessment, IMS utilized their Road Surface Tester which uses a laser-camera array and human input to collect surface distresses, roughness, and rutting data,” he said.
It took a total of four weeks to complete the evaluation.
From there, Schauble said, the pavement condition data was loaded into the city’s current pavement management software.
The laser-camera array, a powerful instrument, identified and collected data on items such as street cracking and rutting.
Once problematic areas were identified, professionals added data pertinent to the street segment such as raveling, trenching, and patching.
Schauble said information gathered was processed and aggregated to give a Pavement Condition Index (PCI) score for each street segment. 
“The PCI scores can be mapped and compared to see where pavement maintenance efforts should be focused,” he said.
The most frequent distress the laser-array calculated was asphalt cracking. This comes with age. Schauble pointed out that when binder oxides, it becomes brittle which leads to cracks.
“As a result, the older areas of a city generally have more distressed pavement and lower PCI scores,” he said. “In Carlsbad, the older areas are the downtown Village area and the La Costa region in the southeast corner of the city.”
The laser-array method also allows the city to be alerted of areas needing repair before the damage goes unnoticed, and in turn, becomes too costly. In the end, the new process saves money.
Schauble said preventative maintenance is key to effectively maintain the city’s paved roadways.  
“For example, streets that are slurry-sealed when they are in fair condition will cost less to maintain over their lifetime than streets that are allowed to deteriorate to a poor condition,” he said.
There are a number of factors used to determine which streets will be rehabilitated each year. These may include the existing condition of the pavement (PCI score), the type of pavement distress, available budget, and the slating of future projects.
Street and road maintenance is continual. 
“The city has about $125 million invested in its pavement and another $66 million invested in its subgrade and aggregate base,” Schauble said.  “In order to protect that investment, the Pavement Management Program must use its funds as effectively as possible.”