Every day 32, 850 drivers cross Big Creek on Windward Parkway and 27,760 cross Lullwater Creek on Ponce de Leon Avenue.
What they almost certainly don't know is that the two bridges, along with 105 others in 10 metro counties, were rated structurally deficient, according to an analysis of the National Bridge Inventory by The Atlanta Journal-Constitution.
Sixty-eight of these bridges have structural components rated poor or worse. Some won't be repaired for years.
Roads departments can't keep up: More bridges across the state have structurally deficient ratings now than five years ago.
As metro Atlanta considers spending billions of dollars to ease congestion with a regional transportation plan funded through a special sales tax, maintaining the area's bridges seems to be a lesser priority.
The special purpose local option sales tax, which goes to voters next year, would pay to rehabilitate seven bridges for $289 million. By comparison, the transportation plan provides $1.1 billion for road widening.
The state spent $73.4 million of its $902 million in 2009 federal stimulus funds on replacing 30 bridges, according to an AJC report last year.
On the positive side, many deficient bridges have been repaired or replaced since the state inspected them last year, according to county highway departments.
Georgia officials have said that, to their knowledge, no Georgia bridge open to traffic has collapsed like the Minneapolis bridge in 2007.
Officials caution against reading the term "structurally deficient" as implying a bridge is on the verge of collapse.
Professional engineers say the state has a vigorous inspection program that quickly identifies deteriorating bridges and county officials say local voters' approval of county sales taxes has made it possible to rehabilitate those bridges.
In some cases, instead of repairing bridges, jurisdictions limit use by weight. This prevents large trucks, if they comply, from using a bridge and further damaging it while allowing smaller trucks and cars to continue crossing.
Some county engineers say the AJC's reporting has made bridges safer recently by drawing attention to problems with inspections and demonstrating why bridge maintenance should be a funding priority.
Even so, if maintenance does not continue to improve, problematic bridges can snarl traffic, hamper growth and, in extreme circumstances, present safety concerns, experts say.
Indiana and Kentucky residents learned that lesson firsthand last week when the I-64 bridge over the Ohio River was closed because of a crack in a load-bearing portion of the span.
"There's a lot of anti-tax and anti-fee feelings right now, but we have to do something to maintain what we have or else it's going to cost more, " said Andy Hermann, president-elect of the American Society of Civil Engineers. "Think about your car. If you change your oil in your car, it will last longer."
Sales tax helps out
Since 2005, one of the 10 metro counties --- Cobb --- has rehabilitated 50 bridges with a special sales tax that began in 2006. County officials estimate the sales tax will have collected $825 million when it expires in December.
Cobb voters recently approved another special sales tax plan that will fund, along with other transportation projects, rehabilitation of eight more bridges. Some are among structurally deficient bridges identified in the National Bridge Inventory and some are bridges the county anticipates will need work in the future.
Bob Galante, a county construction engineer, said his family and friends cross Cobb bridges regularly and he believes the county has made a big push since 2005 to make sure that they and the rest of the traveling public are safe.
He credits stories by the AJC with encouraging the public to invest in infrastructure.
"People have to support funding and [publicity is] the only way they're going to support funding, " Galante said.
He also said state bridge inspectors are more diligent since an AJC story in 2008 about a DOT inspector who admitted filing reports for 54 bridges that he and another inspector had not actually inspected.
DOT officials declined to answer specific questions about bridge maintenance and funding.
But, the National Bridge Inventory shows a slight increase in the number of deficient bridges across the metro area.
In 2006, there were 96 structurally deficient bridges in the region and 54 with structural components rated as poor or lower.
Motorists might see the number grow in the next few years, some experts say.
If traditional sources of road-repair funding, like the gas tax, are not increased, DOT will have less money to inspect the growing number of deteriorating bridges, said Luther Cox, a forensic engineer and former president of the Georgia Society of Professional Engineers.
Gas tax revenue is declining and DOT budget problems have caused decreased spending on road projects since 2007.
"The funding problem is really bad for the future of transportation, " Cox said. "If you keep slashing the budget of GDOT, you won't be able to conduct inspections."
Some county and state transportation employees say concerns over structurally deficient bridges are overstated.
The term structurally deficient sounds scary, but it does not mean a bridge is on the brink of collapse, officials said.
Structurally deficient means a bridge requires maintenance. A relatively minor problem could cause a bridge to be rated deficient, engineers say.
Peter Vanderzee, president and CEO of LifeSpan Technologies, an Alpharetta company that sells bridge monitoring and inspection equipment, agrees that some bridges rated deficient are not in bad shape.
Unfortunately, the reverse is also true and some bridges with sound ratings are in poor condition, he said.
Last month, 170 feet of fencing fell from the 17th Street bridge onto the Downtown Connector below, narrowly missing late-night traffic. The bridge was inspected 18 months ago and rated 94.72 out of 100.
Vanderzee said the visual inspections used by the state provide a poor understanding of any bridge's condition.
South Carolina uses sensors sold by LifeSpan to calculate the strain on bridge components continuously, Vanderzee said.
Lee Floyd, bridge maintenance engineer for South Carolina's Department of Transportation, said the sensors have demonstrated benefits he did not expect.
Floyd said he noticed the strain on a specific bridge spiked late at night when traffic should be sparse.
Investigation revealed logging trucks that weighed more than the posted weight limit were using the bridge at night to avoid police.
"It's a slick system, " he said.
Some engineers say consistent visual inspections, like those performed by Georgia, will identify problems before they become an issue for motorists, but they also anticipate states will incorporate new technology in the future.