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I-43 and County Y project - need/purpose

Need

This project was developed to address the current bridge deck condition of the County Y bridge over I-43. The original bridge was constructed in 1969 and was rehabilitated with a concrete overlay in 1984. The bridge deck has outlived its expected design life and is in need of replacement. Continued maintenance on the bridge deck would not be economical. In addition, the southwest corner of the bridge does not meet current standards for vertical clearance over I-43.

The existing County Y concrete pavement condition is deteriorated with cracking and pavement settlement. Addressing these needs is more cost effective to do in conjunction with the bridge structure improvements.

As part of the project investigation process, traffic volumes are forecast 20 years into the future. Review of projected traffic volumes indicated a need to investigate interchange operations for capacity and safety. This review also included investigating the impacts of the forecasted traffic volumes on the existing freeway.

Purpose

The County Y bridge over I-43 will have the bridge deck removed and replaced. In addition, the bridge deck will be raised to achieve the current standard for vertical clearance.

The County Y pavement will be reconstructed from West College Avenue to Julius Heil Drive. County Y will be reconstructed with concrete pavement for two northbound and two southbound lanes.

The construction of roundabouts on County Y, at each ramp termini, is the selected alternative to address interchange capacity and safety. A comparison was done to evaluate whether roundabouts or traffic signals would provide the most benefits at the ramp termini. Results of the comparison were:

• Roundabouts have a lower initial construction cost than traffic signals. The geometric improvements (turn lanes, storage lengths, etc.) required for traffic signals would require the bridge deck to be widened along the southbound lanes.
• Interchange capacity is increased with the use of roundabouts by the reduction in vehicle delay due to vehicles not having to stop at a red light.
• Interchange safety is improved by the roundabout geometry requiring a reduction in vehicle speeds.
• Interchange safety is also increased by the counter clockwise movement of traffic through a roundabout.  Roundabouts have shown that they help reduce certain types of crashes including head-on and broadside collisions.

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Last modified: May 13, 2009