South Road at Colt Highway and Two-Mile Road Roundabout Project

Client Name
Town of Farmington
Farmington, Connecticut, USA
  • Transportation engineering
  • Civil & structural engineering
  • Landscape architecture

This project received the 2024 Achievement in Civil Engineering (ACE) Award in Municipal Achievement from the Connecticut Society of Civil Engineers.


The subject intersection, previously all-way stop controlled, is located just east of the University of Connecticut Health Center (UCONN Health) campus and serves a significant amount of traffic carrying over 15,000 vehicles daily. The intersection is also adjacent to the Westfarms Mall, the new Connecticut Department of Transportation Park & Ride lot on Colt Highway and less than a quarter of a mile from the East Farmington Firehouse on South Road. With over one-million-square-feet of expansion projects completed within the past 5 years at UConn Health, this intersection which is an important connection to UCONN Health, Westfarms Mall and Interstate 84, experienced significant congestion and queuing during peak commuting hours as well as high crash rates.

The goal of the roundabout project was therefore geared towards alleviating congestion, improving safety within the area, while enhancing active transportation with its associated air quality and environmental benefits.


The project involved the design and preparation of contract documents for a 130-foot diameter single lane roundabout with a mountable truck apron, and a right turn lane on the eastbound approach to alleviate queuing on the South Road Bridge over I-84 to the west of the intersection. Capacity analysis using the VISSIM traffic simulation software was employed to vet the roundabout improvements. Additionally, geotechnical information was obtained and analyzed to inform the pavement design. Accommodations for pedestrians were a key design consideration for the project. Sidewalks with ADA ramps and pedestrian refuge areas were provided on all legs of the roundabout and the sidewalk along Colt Highway was extended to the Park & Ride lot. Additionally, street lighting and streetscape improvements were also implemented to enhance aesthetics for this campus gateway.

The project was designed in line with standards stipulated in the NCHRP 672: Roundabout Information Guide, and American Association of State Highway and Transportation Officials’ (AASHTO) Guide for the Development of Bicycle Facilities, 1999 edition, and Manual of Uniform Traffic Control Devices (MUTCD). CTDOT’s Standard Specifications Form 818, and related supplements applied for the construction of this project, supplemented by Town of Farmington requirements when applicable.

Excellence in the management of the design and/or construction process or design

One of the keys to delivering the project successfully was SLR’s close collaboration with Town of Farmington Engineering staff and the Connecticut Department of Transportation Roundabout Committee throughout the design. Additionally, extensive stakeholder and public engagement which involved meeting with neighbors and the use of visualization techniques to effectively communicate the proposed improvements helped garner support for the project.

Accomplishment of project objectives in the face of significant challenges

Colt Highway roundabout project during construction

Construction of this multi-modal roundabout in this busy area presented its fair share of challenges. Great care was taken to minimize disruptions to vehicular and pedestrian traffic during construction. To effectively do that, construction staging, and site-specific Maintenance & Protection of Traffic plans and pedestrian detour plans were developed to ensure travel disruptions were minimal and that access to UCONN Health and neighborhoods could be maintained at all times. Furthermore, while the project involved extensive utility coordination, a maze of underground utility lines and duct banks were encountered during construction which required our team to quickly redesign some drainage structures and laterals to avoid conflicts and ensure the project remained on schedule.


There has been a notable improvement in traffic flow with little to no congestion being experienced during peak hours at the intersection. The Town was thrilled with the project outcome as it met the goals of alleviating congestion and safety while enhancing multi-modal connections in the area.

"The success of this project is due to the design team of SLR and their commitment to listen to the Town Staff, the neighbors and incorporate suggestions into the development of the plans."

Russ Arnold, Town of Farmington Director of Public Works/Town Engineer