Construction of the new Tappan Zee Bridge is about 50 percent completed, according to engineers.

"The first year of this work, most of this work was taking place below the water, driving piles," said Thruway Authority construction engineer Tom McGuiness. "So although the engineering front knew where and how much work was being done, it really wasn't visible. Now seeing it take place, it's a good feeling."

In recent months, construction above the water line has moved into high gear, with numerous sections of steel girders going up once or twice a week. Work is also moving along on the concrete supports for the roadway. Big blue boxes on the span will eventually produce the bridge's iconic profile.

"Each one of these structures represents what will be the start of the construction of the pylons, or the towers that make up the main span of the bridge," says McGuinness.

Work has also begun on the main towers, which will carry the new span across the Hudson River, a major milestone in the construction of the new bridge.

The towers will go up in segments, with the large blue concrete forms gradually rising from the football field-sized bases. Tower cranes, which are anchored bases, will help with the work.

The work will continue on the bridge well into December, if weather permits.

While work on the new span is moving along on schedule, there is still no word from state officials about tolls once the work is done