Conceptual Layout

The intersection of Robert T. Longway Boulevard and Walnut Street was included in the early preliminary engineering phase with support from of the City of Flint due to intersection operations and future plans to close Kearlsey Street at Walnut and make the intersection at Robert T. Longway Boulevard and Walnut Street the eastern entrance into the Flint Cultural Center. This intersection is a secondary analysis Tier Three intersection.

During the skim analysis, it was observed that there were two angle crashes and zero head on left turn crashes over the 5-year period. These crashes resulted in no fatalities or type A, type B, or type C injuries at the intersection.

The intersection of Robert T. Longway and Walnut Street is a two-way stop control intersection. Robert T. Longway runs east/west and is a four-lane roadway with two lanes in each direction. Walnut Street runs north/south and is a two-lane road with one lane in each direction. The Walnut Street approaches are stop controlled.  In the southwest quadrant of the intersection is a Consumers Energy electrical sub-station. The Buick Gallery is located adjacent to the right-of-way in the southeast quadrant. To the north of the intersection is vacant property owned by the City of Flint but there are high-voltage power lines that run east/west overhead. 

An operational analysis of the no-build condition was completed for the intersection using the 2045 forecast traffic volumes. The results of the analysis for future no-build conditions reveals that all approaches and movements of the intersection operate at LOS C or better during the AM and PM peak hours.

The 95th percentile queue lengths were reviewed at the intersection and results showed that all approaches experienced a maximum queue length of 48 feet (2 vehicles) during the AM peak hour and 44 feet (2 vehicles) during the PM peak hour. 

The operational results for future no-build conditions are presented in the table below.

Due to the current four-lane cross-section on Robert T. Longway Boulevard, two potential roundabout layouts were developed. A two-lane by one-lane roundabout was drawn that allowed for a two-lane approach for eastbound and westbound Robert T. Longway and a single-lane approach for Walnut Street. Because of the location of both the Consumers Energy electric substation and the Buick Gallery, the roundabout was offset to the north of the current location. The property to the north of the intersection is owned by the City of Flint, therefore no additional right-of-way would be needed to accommodate this shift. Although no additional right-of-way will be necessary, the Consumers Energy easement and overhead power will need to be relocated to accommodate a proposed roundabout. A full layout can be found at the end of this section. 

An operational analysis of the roundabout (build) condition was completed for the intersection using  the 2045 forecast traffic volumes. The results of the analysis for roundabout (build) conditions reveals that all approaches and movements of the intersection operate at LOS A during the AM and PM peak hours.

The 95th percentile queue lengths were reviewed at the intersection and results showed that all approaches experienced a maximum queue length of one vehicle during the AM peak hour and PM peak hour for the 2 by 1 layout and 2 vehicles during the AM and PM peak hour for the single-lane roundabout. 

The operational results for future roundabout (build) conditions are in the table below.

A separate traffic analysis was completed to determine the feasibility of a roundabout with an event at The Whiting. A trip generation was performed for The Whiting based on a 2,043-seat venue. A 50/50 split was used for distribution of vehicles leaving using Kearsley Street and Walnut Street. It was determined based on a trip generation rate from the 9th Edition of the Trip Generation Manual, there would be a total of 41 trips (21 in, 20 out) generated during the PM peak hour. The table below represents the trip generation.

This results in roughly five to six vehicles generated using Walnut Street to enter/exit The Whiting.  Special events typically do not occur during the typical peak hours (7-9 a.m. and 4-6 p.m.). To create a more conservative case, 200 vehicles were added to the major movements entering/exiting The Whiting at Robert T. Longway Boulevard and Walnut Street: northbound right and left turning movements, eastbound right turning movement, westbound left turning movement. The table below presents the operational results for a single lane roundabout with a special event at The Whiting

Based on the addition of event traffic, a proposed single lane roundabout will operate with acceptable LOS during an event at The Whiting.

A roundabout would be feasible at this location, although it would be quite costly due to the necessary relocation of the Consumers Energy power lines. If the City of Flint moves forward with a road diet on Robert T. Longway east of northbound Chavez, a single-lane roundabout would be desirable.

Opinions of probable costs were developed for both scenarios. The 2 by 1 roundabout probable cost is $1.61 million in year 2025 dollars. The single-lane roundabout probable cost is $1.39 million in year 2025 dollars. These probable costs include a 20 percent contingency and 3 percent annual inflation. The potential fees from Consumers Energy to relocate their high voltage poles to accommodate the proposed layouts was estimated to be $200,000 based on information provided from Consumers Energy.

Potential funding for this improvement could be made possible by regular road improvement funding or an earmark. There are no significant crashes of the type that would make the intersections eligible for safety funds and the intersection does not experience enough delay to make it eligible for CMAQ funding.

For a complete breakdown of the estimate please review the full report below.