Background

In the fall of 2008, St. Louis County and the Hanley Road design team investigated an alternative concept to the Single-Point Urban Interchange (SPUI) originally proposed for the intersection of Hanley at Manchester Road. The primary reasons for the investigation included the following:

• Reduce construction cost
• Reduce the physical and visual impacts of a grade separation
• Improve pedestrian, bicycle, and transit access
• Improve access to local businesses

Essentially, the Median U-Turn Intersection (MUTI) did accomplish these objectives. And, most importantly, these objectives were accomplished without compromising safety and regional mobility. In February 2009, St. Louis County modified the intersection design. This page will provide a description of what a MUTI is, why it’s being implemented at this location, and an overview of what it will look like and how it will function.

The animations below have been developed to demonstrate how each of the four left-turn movements at the Manchester Road intersection will be made.

What is a MUTI?

A MUTI (or Median U-Turn Intersection), also known as a “Michigan Left” because of their prominence and early implementation in parts of that state, is an at-grade solution that greatly increases capacity at intersections. In general, direct left-turns are replaced by median u-turns along one or both cross streets. Figure 1 below illustrates the basic geometry of the planned intersection (note that landscaping and pedestrian amenities are not shown for clarity and will be developed as part of the detailed design of the project).

Figure 1. Proposed Geometry for Hanley MUTI.

Why a MUTI for Hanley at Manchester?

A MUTI, with a large median footprint, requires as much or more right-of-way than the tight single-point interchange originally planned. So what are the advantages of implementing one here? The reasons are many, but the five most important reasons are detailed as follows:

1. Capacity. Detailed traffic engineering, which factored in major redevelopment plans and regional growth was performed for the MUTI and compared to similar models for a traditional at-grade intersection and a single-point interchange using SYNCHRO and VISSIM analysis tools. Overall, the MUTI performs at the same level-of-service as the single-point during peak traffic conditions. The traditional intersection does not adequately handle traffic under these conditions.
2. Cost. Even with the additional right-of-way requirements, the anticipated savings of a MUTI over a single-point interchange is anticipated to approach $10M.
3. Access for all modes of travel. The MUTI not only affords driveway access within a reasonable distance of the intersection (where single-point interchange ramps prevent access), other forms of transportation benefit. Transit bus stops can be incorporated where single-point ramps prevented it, and pedestrians and bicycles have greatly improved access with a level of safety much greater than that of a typical at-grade intersection.
4. Aesthetics. Based on numerous discussions with project stakeholders, the visual barrier through this area created by a grade separation came up too often to ignore. For that reason, a careful review of what the corridor would look like with a MUTI treatment was undertaken. As depicted in the rendering below in Figure 2 and the traffic simulations found here, a MUTI will definitely have a positive aesthetic influence on the Hanley corridor and local community.
5. Flexibility. In comparison to a single-point interchange, a MUTI is extremely flexible in terms of accommodating redevelopment and controlling capacity. Depending on the pace of redevelopment and/or availability of construction funding, St. Louis County could opt to construct the through-lanes in phases over time (though the current plan is to construct all three through-lanes in both directions at one time). In terms of redevelopment, since access points along both Hanley and Manchester can be allowed in closer proximity than a single-point afforded, consideration for adding access points to accommodate future redevelopment can be given. Also, intersection capacity could feasibly be increased if warranted in the future by extending the u-turn storage lane through the Manchester intersection (which would require a reduction in the median width).

Disclaimer: Artist rendering, actual project may differ from illustration depending on agreements and availability of funding.

Figure 2. Artist Rendering of Hanley Road Near Intersection with Caroline Avenue Looking North.

How will a MUTI at Hanley/Manchester Function?

St. Louis County has developed graphics and simulations of how the corridor will look and function in the vicinity of the Manchester Road intersection. Figure 3 below depicts the two basic movements, one each for a left-turn from Hanley and a left-turn from Manchester. Also, animations have been developed that demonstrate how each of the four left-turn movements at the Manchester Road intersection will be made (see above). As this project develops, stay tuned for additional information.

Figure 3 – How to make a left turn for Hanley Road (top) and Manchester Road (bottom).