Digital road inventory spurs Travis County five-year road plan
Buffalo Grove, Illinois
In central Texas, an inventory of Travis County roads from an automated digital imaging system is enabling the county to more effectively program road maintenance through a five-year plan, while meeting GASB 34 requirements.
The system digitally photographed all county road surfaces during the period of May through September 2004, created a condition database, and engineers then rolled the data over into an off-the-shelf pavement management system (PMS) which Travis County uses on a daily basis. The county now has a database which will let them access images of pavement conditions all throughout the county, in seconds.
"We now have a real-time snapshot of our road system," said Don Ward, P.E., Division Manager, Road & Bridge Maintenance, Travis County Transportation & Natural Resources. "The survey has really opened our eyes as to the exact condition our roadway is in."
This was done via a digital imaging survey. "The engineers utilized a van with some highly sophisticated digital imaging equipment, which measured all of our 1,220 miles of roadway—our maintained Travis County roads—using distress factors," Ward said. "In conjunction with our PMS it gave us a five-year pavement management plan based on their digital imaging and distress analysis of all our roads."
According to Ward, most of the survey work was done last summer and the reports were finished by December 2004. "We now use that five-year plan as a guide, and our Pavement Management Engineer prepares an annual work plan based on that initial plan," Ward said. Scott Lambert, P.E., is PM Engineer.
The PMS module now is linked with Travis County's geographic information system (GIS). "We now can actually go to an individual road segment, pull it up, and go to a particular point on that roadway and examine the digital image," Ward said. "Perhaps the module indicates that we have a bad level of distress at a particular point. We can go to that point, and actually see what's there without having to drive out there. The inventory is a benchmark that we can use to track how well we improve the road system in the future."
Work done at night
The engineers did their work at night, Ward said. "It's a very interesting method, using strobe lights that were directed at the pavement," he said. "By shooting at night they avoided daylight shadows that could have interfered with the imaging. They drove every foot of our road system, taking 14-foot-wide samples at a time. It looked like a spaceship coming down the road. I had people calling me about a strange thing with flashing lights coming down the road, asking what was going on!"
The system used was the ADVantage (Automated Distress Vehicle) system of Fugro Consultants LP, the industry's first completely automated digital pavement distress surveying system. The ADVantage system brings together imaging and computer analysis of those images to construct a reliable database of pavement conditions, with substantial savings in time and labor costs.
The digital image capture system, data storage system, and data analysis system are all housed in a customized van, which is operated at night, or in low light, with four strobe lights to guarantee optimal illumination for capturing high-resolution (1296 x 1024 pixel) digital images of the roadway.
The images are fed into an onboard computer system where they are stored and sequentially analyzed in real time to identify the quantity and severity of cracks. Crack severity statistics are stored in a separate database. The data are analyzed for longitudinal, transverse, block and alligator cracking patterns, and are geographically referenced with universal GPS/GIS coding.
A single high-resolution camera is mounted over the roadway from the rear of the van. The camera acquires up to 12 frames of digital images of the roadway per second. A digital image of the entire lane, 14 feet in width, is captured from the back of the van, with sequential longitudinal images stitched together by the processing software.
These images are analyzed to identify cracks and cracking patterns using optical character recognition based on pixel variations within the digital photos. This system automatically distinguishes between manufactured joints in concrete rigid pavement sections, and joints at bridge approaches, versus pavement distress. Also, an optional laser rut bar is provided on the ADV to capture pavement roughness and ride data.
"During this process we had monthly meetings, and a final review, but the engineers worked on their own," Ward said. "We went through the database very closely to see if there were any glaring errors. We also drove some of the roads to correlate our section managers' concepts with what the model said it was. It pretty much matched up."
Rolled-over into PMS
With this system, acquired pavement distresses are identified, categorized and summed per the rules of the owning agency, and then these data can be "rolled over" into the agency's existing pavement management system (PMS) database.
In Travis County, Fugro used the county's existing CarteGraph PAVEMENTview Plus software module to build the database. "We now can analyze reports using our software to develop our annual maintenance and work plans, based on our budgets, so we can maintain our roads in a good to fair condition," Ward said.
This replaces an old "windshield survey" analysis done previously. Back then, the county's consultant looked at about 10 percent of the roadway, and extrapolated his pavement condition analysis from that fraction. "It was before my time, and it was not as effective as it could be," Ward said. "When I got here just under two years ago, one of my first duties was to come up with a better pavement management program."
Now county management is firmly behind the system. "We're really 'gung-ho' about the system," Ward said. "We want to stay ahead of the game. We had the dollars budgeted, did what we needed to do, and our challenge was to find the right software program and the right consultant to do the inventory."
That's not to say the county was sold on the digital imaging to begin with. The county did not specify any particular method in its RFP.
"We took proposals that varied widely," Ward said. "Some proposals would have used windshield surveys, some with digital imaging. We got a better, faster product out of the process. It's a great database, and we're hoping to enlarge it by using available stereoscopic imagery in which the entire right-of-way can be captured, including drainage structures, signs and light standards. We need to repeat this inventory every few years to bring it up to date, and more than likely we will have that done the next time."
Meeting GASB 34 standards
The high-speed pavement inventory also allowed Travis County to meet the new GASB 34 accounting standards now influencing how government agencies balance their books. GASB 34 is bringing the accounting standards of the business world to that of government, and its pavement management element dovetails with the asset management philosophy being promoted by the Federal Highway Administration. To the FHWA, local government asset management is pavement (and bridge) management.
GASB 34 is short for Government Accounting Standards Board Statement 34, which requires that state and local governments include the value of long-lived assets, including roads and bridges, in their annual financial statements.
Early on, the importance of GASB 34 was not lost on Travis County. "This is the most significant and comprehensive change to state and local governmental accounting and financial reporting in many years," said Christian R. Smith, Executive Manager, Planning and Budget, for Travis County in December 2001. "The intent of these changes is to improve governments' accountability in financial reporting and provide additional financial information. Not meeting this requirement would inevitably have a negative impact on the county's bond rating."
"We worked with our financial department to get the information they needed to fulfill the GASB 34 requirements," Ward said. "We learned our roads were in better shape than we thought they were. By looking at every mile, it pointed out some areas that had been overlooked when we did 10 percent of the roads. It gave us an idea of how we can tie everything together—PMS, GIS and GASB 34—and work together in a more cooperative, more productive effort."
The county classes its road surface conditions as poor, marginal, fair and good. Now, the county knows for sure that over 70 percent of the roads on average are rated fair to good, but that doesn't hold up across the county's four precincts, where some are above 90 percent fair to good, but others well below.
"We're looking to get all precincts up above 80 percent within the next year or two," Ward said. "But we're ahead of the curve on this, and the survey really helped a lot. This gives us one more tool that we can use to distinctly point out where our problem areas are, and bring them up to good or fair condition."
Travis County has posted its road improvement plans, county-wide and by precinct, on the Internet. You may review them at http://www.co.travis.tx.us/tnr/roads/default.asp.
Tom Kuennen can be reached at (847) 229-1839 or firstname.lastname@example.org.