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New Mexico State University

New Mexico State University

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Student engineers assist NMDOT with highway condition assessments

"The New Mexico State Highway System affects the life of every New Mexican, everyday," points out Robert S. Young, New Mexico Department of Transportation pavement preservation engineer.

New Mexico State University civil engineering student Jaime Saenz Garcia and professor Paola Bandini assess the condition of a New Mexico road as part of a Department of Transportation funded program. Civil engineering faculty and students at NMSU inspect more than 7,500 miles of highway every year (NMSU photo by Darren Phillips)

While the responsibility of assuring the safety of the traveling public on highways in the state lies with NMDOT, civil engineering faculty and students at New Mexico State University make a big contribution toward that end. They inspect more than 7,500 miles of highway every year.

Trained by experienced NMDOT staff and faculty, 12 students spend the summer conducting visual examinations of a portion of every mile of pavement of state roads and highways in southern New Mexico. Their peers from the University of New Mexico inspect the highways in the north.

NMDOT first used NMSU students to evaluate highways in the 1980s, but went back to performing inspections with their own staff. In 2006, they resurrected the program on a one-year trial basis and have subsequently renewed for four years.

"The State of New Mexico is very happy with its partnership with the universities. They're our eyes," Young said. "This successful partnership frees up NMDOT engineers to concentrate on highway construction and maintenance projects. The NMDOT could use an outside vendor to assess the state highways, but that would likely cost three or four times as much. And we think the data collected by the university pavement inspectors is actually better."

Equipped with fluorescent vests and hats and using a rut bar, the student inspectors look for eight types of distresses in the pavement surface such as cracks, patches, ruts and other signs of deterioration. Stopping at every mile marker to examine a 10th of a mile of pavement, the students evaluate and record the severity and extent of the conditions on a scale of zero to three. After the field evaluation, the students input their data in laptop computers and pass it on to the graduate students at the end of each week. The graduate students evaluate the quality and completeness of the data before it is reported to NMDOT.

The data is compiled into the state's annual report on the conditions of New Mexico highways and used to determine if routine maintenance or rehabilitation is needed. It can also be used to develop deterioration and performance models that can predict future pavement conditions.

"The accuracy of the information gathered by our students is very important to the safety of the traveling public as well to taxpayers - very important decisions are based on the information that is derived from this data," said Paola Bandini, associate professor of civil engineering who administers the project.

"The pavement condition data collected as a result of the Department's Pavement Inspection Program are the factual basis for making investment decisions affecting many millions of dollars of taxpayer money," Bandini said. "The 26,570 lane miles of paved highways in the New Mexico State Highway System are by far New Mexico's largest material investment, worth more than $15 billion."

Bandini notes that the state benefits from related ongoing research projects at NMSU.

"Through one of our research projects, we've been able to make quality control improvements since 2006," Bandini said. "There is a lot of subjectivity in the data when more than one person conducts a visual evaluation of the pavement. We developed a new statistical model to determine the reliability of the data. It's great when we can apply our research to provide the best evaluations that we can."

The model compares the ratings of two parameters: distress severity, the width of the cracks and the depth of rutting; and distress extent, the percentage of the section that is affected by a particular condition. This methodology is used during the production stage of the project, comparing the evaluations of randomly selected pavement sections carried out by the student inspectors with evaluations that were done previously on the same sections. If a discrepancy occurs, the section is evaluated again and inspection procedures are reviewed.

Civil engineering students are also helping NMDOT transition from using manual rut depth measurements to using automatic data gathered with infrared displacement sensors mounted in a van. The sensors measure pavement roughness and rut depth - the depth of the two wheel path ruts that occur in highways. If too deep, the ruts could cause a hazard.

NMDOT currently relies on data gathered by student inspectors who lay a 4-foot straight bar across the pavement to measure rut depth. Their visual inspections yield ratings from 0 to 3 for both severity and extent of rutting for 1/10th mile sections, while the infrared sensors give an average of continuous measurements, mile by mile.

Graduate students have completed a statistical analysis comparing the rut depth data gathered by sensors to that gathered manually over the past five years. Now they must develop a method to make the measurements equivalent. If successful, students could eliminate the rut measurement from their inspections and possibly make other assessments needed for the state's pavement management system.

A total of 48 undergraduate students have participated in the highway inspection program, along with a number of graduate students.

"It's a hard job - students are traveling all the time and they walk from four to six miles each day in the hot sun. And yet, it's a very popular program," Bandini explained. "This year we had four students returning to the program and 95 students applied for the eight remaining openings.

"The students gain not only the academic knowledge, but also learn leadership, planning, engineering judgment and reliability - things they don't get exposed to in the classroom," Bandini said. "It also makes them more competitive in the job market, whether they go to work for a department of transportation or in private industry."