The agency agreed to add lanes within the existing right of way.

But the study found that in the short run, adding lanes would increase demand for road space by 20 to 60 percent.

"Now people keep coming right through Jan. 1 and this is a hot location, particularly since two lanes are being added to the highway."

A bike and pedestrian lane will be added to the new bridge.

When the $75 million project is completed, one additional lane will be added in each direction, along with the wider new bridges.

The idea is similar to adding lanes to a freeway to improve traffic flow.

An extra lane is added on the left, widening the freeway to four lanes.

As a second viaduct was not considered viable, the new lanes will be added underground from 2012 on.

In the meantime, additional passing lanes may be added.

Since then, additional interchanges and lanes have been added in places to accommodate traffic needs.