Netherland Inn Bridge Update 3/3/03


	TDOT has not yet completed their final plans on the new bridge but they shared preliminary design plans at a field review meeting with City staff in November 2002. In their initial design for the alternative bridge, TDOT was showing the new bridge to be slightly sloped from east to west -- with the high end of the bridge on the park side and the low end landing on the Rotherwood side. Based on this design Netherland Inn road would also have to be adjusted to provide smooth transition at each end of the new bridge.

	How much the roads have to be adjusted (both up and down, and side to side) is driven by engineering standards for roadway design that are based upon the design speed of the road. For each speed there are specific vertical and horizontal limits for acceptable slopes. In general, the slower the design speed the more sloped the transition between the bridge and the adjoining roads is allowed to be and likewise the faster the speed the lower the tolerance for changes in elevation. These standards are all based upon traffic safety requirements.

	In their initial design, TDOT staff reported that they had to lower the western-most part of the bridge in order to match the existing driveway height for the Rotherwood Mansion which is 4-6 feet below the height of the existing Netherland Inn Road. However, lowering Netherland Inn to the height of the Rotherwood Mansion driveway subsequently creates problems at the Netherland Inn / Rotherwood Drive intersection.