How Technology Can Stretch Infrastructure Dollars
A bridge-monitoring system used in South Carolina and other states is helping to hold down the costs of maintenance.
The gap between what it would cost to properly maintain and upgrade America's infrastructure and what governments currently spend is vast. Technology alone can't bridge the gap, but the more we learn about its applications, the clearer it becomes that technology can significantly narrow that chasm.
One example comes from South Carolina, where an innovative bridge-monitoring system is producing real savings despite being in use on only eight bridges. Girder sensors installed on a bridge can measure its carrying capacity and be monitored 24/7. The monitors don't eliminate the need for inspections, but the technology does make the need less frequent.
Thanks to the new technology, the South Carolina Department of Transportation (SCDOT) has learned that inspectors tend to underestimate bridge strength. Real-time information from the monitors allows SCDOT to keep bridges in service for up to an extra five years before replacing them. It also has led to the elimination of weight restrictions and to keeping one bridge open that would otherwise have been closed.
In another case, data from the monitors led SCDOT to solve a bridge's problems with a $100,000 retrofit rather than spending $800,000 to replace it. All told, having the monitors on just eight bridges, at a cost of about $50,000 per bridge, has saved taxpayers $5 million. When you consider that South Carolina has more than 8,000 bridges and that similar systems are being used in Arizona, Michigan, North Dakota, Pennsylvania and Utah, the potential savings are huge.
MAP-21, the latest federal surface transportation authorization, might lead more states to embrace bridge monitoring because it requires them to have asset management plans, which help governments minimize lifecycle costs by identifying when it makes sense to invest in maintenance as opposed to replacing an asset. An example of the importance of investing in maintenance comes from Boston, where repair of a single bridge is costing Massachusetts taxpayers more than $180 million. One study found that doing routine maintenance over the 100 years the bridge has been in service would have saved over $80 million.
Determining structural integrity is not the only benefit from installing the monitors. They can also determine wind speed, which allows SCDOT to know when to close a bridge without, for example, having to send an employee to the site during an approaching hurricane.
Overweight vehicles can be particularly damaging to bridges. Late one night, an SCDOT bridge maintenance engineer noticed that the sensors were indicating that one bridge was under a great deal of strain. He sent law enforcement to investigate and the offers found logging trucks above the posted weight limits using the bridge. Needless to say, the drivers were ticketed.
Advances like using electronic tolling for congestion pricing have proved to be an effective way to use technology to maximize revenue from transportation assets. South Carolina and other states are demonstrating the value of technology on the cost side of the infrastructure ledger.