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SDOT Goes Hi-Tech to Analyze Roads


If you’ve seen this strange looking van on Seattle streets in the past three months, you weren’t looking at just any van – that was the ARAN (Automatic Road Analyzer ).   SDOT has been utilizing the hi-tech van to analyze the condition of Seattle’s arterial streets since 2003. The analysis is done every two to three years.  This is the fourth time the evaluation has taken place.  It takes about three months for the ARAN vehicle to cover all the city’s 1,531 lane-miles of arterial streets. 

How does it work?  Well, in basic terms, the ARAN Van has four cameras that take pictures of the street surface as well as the street face—90 degrees from the front of the van. With lights flashing in the back and towards the pavement surface for the cameras, the van drives down every lane of every arterial street in the city collecting photographic images.  In addition, the van is equipped with Geographic Positioning Systems (GPS) and laser sensors that measure roughness and irregularities.

Knowing specifically the type of pavement distress present on each roadway helps SDOT determine the most cost effective way to maintain each street.  The information from the ARAN is particularly helpful in identifying locations where preservative measures can extend the life of an existing pavement.  Data from the ARAN is fed into SDOT’s pavement management system to determine a condition rating for each arterial street section.  Pavement condition can be mapped along with traffic volumes, transit routes, high pedestrian locations, reported potholes and other data.  This allows staff to determine where pavement improvements will benefit the greatest number and widest range of users.