Road Safety Audits (RSA)

APPENDIX A
RSA CASE STUDIES

RSA NUMBER 4

WISCONSIN DEPARTMENT OF TRANSPORTATION:
RSA OF IMPROVEMENTS TO MARQUETTE INTERCHANGE

PROJECT BACKGROUND:

Highways I-94, I-794, and I-43 meet at the Marquette Interchange in Milwaukee. The interchange, considered the cornerstone of the southeastern Wisconsin freeway system, accommodates Milwaukee’s commuter traffic, as well as interurban traffic traveling to and from Madison, Green Bay, and Chicago, and long-distance interstate traffic. Reconstruction of the existing interchange, which built in 1968, was required to address structural deterioration and operational concerns. At the time of the RSA in December 2003, planning and design for the reconstructed interchange had been ongoing for several years, and construction was to commence in about six months. The RSA examined both the proposed changes and construction-stage plans, since the interchange was required to remain operational throughout the four-year construction period. The existing and redesigned interchanges are shown in FIGURE A.5. The total cost of the interchange reconstruction was anticipated to be $800 million.

Existing Interchange	Improved Interchange (simulation)

FIGURE A.5 EXISTING INTERCHANGE AND PROPOSED IMPROVEMENTS

The planned reconstruction includes upgrades and improvements include:

• replacement of left-side ramps with conventional right-side ramps,
• lengthening or elimination of existing short weaving sections,
• increased curve radii on ramps,
• lane continuity and consistency for through traffic,
• increased capacity on system ramps,
• increased barrier height.

KEY RSA FINDINGS AND SUGGESTIONS:

The key findings and suggestions of the RSA are summarized in TABLE A.4. In their response, the design team accepted a number of suggestions that could be implemented at the late design stage for this RSA, but declined suggestions that would entail revisiting the public involvement, design, or environmental assessment processes. A number of suggestions were identified as already in the design plans (see discussion below on document control under “Lessons Learned”). Where signing could be retroactively deployed to correct a safety issue (Issue 2), the design team suggested monitoring operations after improvements were completed to confirm whether the safety issue would actually occur before implementing suggested signing changes.

KEY LESSONS LEARNED:

RSAs conducted late in the design process require a selective focus to be effective. The Marquette Interchange RSA was conducted at an advanced stage in the interchange design, after the completion of the public involvement process, and was consequently limited in the range of items and suggested alternatives that could usefully and practically be identified and implemented. Fundamental design elements had to be taken as “given”, since changes to them were impractical at the advanced stage that the RSA was conducted. Consequently, the RSA team focused on elements of the design that could be amended or mitigated at the detailed design stage.

Time constraints require that the RSA team direct its efforts and use its time efficiently. As is typical for design-stage RSAs, this RSA was on the critical path in the Interchange design schedule. The RSA team had less than five days to review a comprehensive interchange design that had been many years in the making. The RSA was therefore limited in its level of detail. Consequently, the RSA team split into two- or three-person teams to cover the interchange elements as comprehensively as possible. The RSA team presented its preliminary findings to the Owner and Design Team after the RSA analysis session, and followed up with the RSA report. The design team issued a timely response to the RSA, outlining what actions had or would be taken. The entire RSA process was completed within three months.

Document control is an important element of the RSA process to ensure that the RSA is based on the most recent design drawings. As with all very large design projects, the Marquette Interchange design generated a vast number of drawings and other documents. The RSA team based its review on drawings which, in some cases, had been superseded at the time of the RSA. The inadvertent inclusion of superseded drawings in the RSA materials reflected the large volume of design documentation on this very large project that was in its final design stages, and the resulting document control issues.

Specialists contribute valuable insight on the RSA team. Members of the eight-person RSA team had a general knowledge of road safety, geometric design, and traffic operations, but several members also had specialized knowledge in various areas. The RSA team included an officer from the Milwaukee County Sheriff’s Office who had extensive experience as a patrol officer on the existing interchange. The insights offered by the officer regarding driver behavior helped the design team to realistically assess the risk associated with design elements and the effectiveness of suggested improvements.

The success of the RSA was promoted by early management of expectations, and by a cooperative approach on the part of all participants. At the start of the RSA, the RSA team explained to the Design Team and Owner what could feasibly be audited within the constraints of the time available and the advanced design stage. At the same time, the Design Team outlined its constraints in terms of the trade-offs that were a necessary part of the design process. This exchange promoted an understanding on the part of all participants concerning what could feasibly be achieved in the RSA. Prior to the start of the RSA, the Design Team responded to the RSA team’s request to identify design issues that they felt the RSA team could assist with. The Design Team identified twelve issues, such as complex intersection channelization and the need to obstruct improper or prohibited vehicle movements (such as wrong-way movements onto exit ramps). The RSA was conducted in the Design Team office, and the Design Team made available a senior designer to answer the RSA team’s questions and clarify issues. This continual liaison enabled the RSA to be completed in the limited time available.

See also the discussion of “Key Factors for Success” and “Lessons Learned” in the main text.