About
The program maintains over 420 miles of roadway across unincorporated Marin County, and the condition of that road network is crucial to the daily lives of the diverse communities of Marin. Keeping the roads network operational is a major responsibility and massive undertaking for Public Works, requiring year-round strategic planning. In addition to focusing on maintaining this infrastructure, the specific goal of improving overall roadway condition has been one of the main priorities for the Marin County Board of Supervisors since they initiated the Road & Bridge Rehabilitation Fund in 2014 to support this program.
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Assessing road quality
The "Pavement Condition Index" (PCI) is a numerical grade between 0 and 100 that is used to indicate the general condition of road pavement. A ranking of zero to 25 is “Failed,” 25 to 50 is “Poor,” 50 to 70 is “At Risk,” and 70 to 100 is “Good.” A score of 100 would be a newly paved road.
Originally developed by the United States Army Corps of Engineers as an airfield pavement rating system, it was later adapted for roads and has become the national standard. The scoring is determined by independent engineering consultants using standardized methods of visual surveying. Many factors affect PCI including pavement age, climate and precipitation, and traffic loads. The numerical grade helps County staff track the service life of the road network, and in turn, prioritize roads that need to be re-paved or rehabilitated. Similarly, PCI helps staff identify roads which could benefit from pavement maintenance treatments, like surface sealants, which help extend service life of a road and avoid the need of more extensive rehabilitation projects.
Paving program approach
In terms of making road improvements, projects become exponentially more intensive and expensive as the condition of the road deteriorates. A good road generally only requires preventative maintenance projects to keep it in good standing, whereas a failed road needs full-depth reconstruction that is a costly and time consuming. For example, $1 million could fund maintenance for 15 miles of good roadway versus only 1 mile of failed roadway being rehabilitated.
The paving program, revised in June 2021, utilizes the PCI scores and strives to keep the roads that are in the "Good" category in that condition by completing a maintenance cycle every seven years. Funding is allocated accordingly to first maintain the roads in the good condition category and then address targeted roads in the other three categories, eventually bringing those roads up into the good condition category. The ultimate goal is to have the full County-maintained roads network reach "Good" status.