Roundabouts: Safe Intersection Solution for Tight Spaces & Budgets

A new roundabout debuted on July 27 at the intersection of Carey Road and 171^st Street in Westfield Indiana, bringing safer travel to an increasingly busy intersection. Carey Road is a highly traveled Westfield arterial, and recent years have seen growing traffic on the side streets that intersect the thoroughfare.

“Over the course of time as neighborhoods have really developed, more and more traffic uses the minor side streets to enter Carey Road,” said GAI Transportation Engineer Jay Vorisek, PE. “That has resulted in more and more delay, and more opportunity for collisions at this intersection.”

While improved safety for drivers and pedestrians coupled with eased traffic flow was the primary goal, there were other significant considerations for the roundabout project as well. “Westfield’s City Engineer was seeking a design that was not your typical size for this type of project,” said Vorisek, who has taken part in more than 85 roundabout projects and was lead designer of the Carey Road/171^st Street roundabout. “Also, typical construction costs can run well over $1M—as this project was going to be locally funded, the client was looking for something about half of that cost.”

Reducing Size, Right-of-Way Demands, and Costs

“Roundabouts provide both safety benefits and long-term cost efficiencies as compared to traditional signalized intersections. However, these benefits are partially offset by the higher up-front costs typically associated with roundabout construction and right-of-way needs,” said Westfield City Engineer Johnathon Nail. The GAI team addressed these challenges with an innovative design that contained the roundabout to a footprint that would not require securing expanded right-of-way, kept existing utilities in place, and utilized existing drainage structures.

“Rather than a full reconstruction of the intersection, which is typical for roundabout projects, this improvement was more of a roundabout conversion,” said GAI’s Brian Craig, PE, who was project manager on the Carey Road/171^st Street roundabout. The existing stop-controlled intersection was converted to a roundabout geometry by constructing a center island, splitter islands, and minor pavement widening at the corners. Site conditions and drainage patterns made it viable to retain the intersection’s existing storm sewers, which yielded significant cost savings by making it possible to re-utilize existing pavement that would otherwise have been demolished and rebuilt.

“By improving efficiencies to fit the local budget we were able to streamline the process, avoid federal red tape, and deliver the project very quickly,” said Vorisek. “A federal aid-funded project would have taken 5 or more years to be completed and open for use.”

Accommodating Large Vehicles in a Small Space

One design challenge was the need to accommodate occasional tractor trailers and other large vehicles within the roundabout’s limited curb lines.

“We designed the roundabout to allow large vehicles to come over the top of the curb and run over a grassy sidewalk buffer space that was reinforced to take the vehicle’s weight,” said Vorisek. In this design the roundabout’s sidewalk buffer spaces were constructed with a honeycomb-like plastic grid incorporated into the landscaping. “The reinforcement system is filled with a stone and soil mixture to give it structure and then sodded on the surface,” said Vorisek. “On the rare occasions when a large vehicle traveling through the roundabout rides over this area, it will make a little bit of a depression but not cause damage that is going to destroy the turf or become unsightly.”

Roundabout Earns Kudos from Residents and Client, and Is a Point of Pride for GAI Team

The Carey Road/171^st Street roundabout received an enthusiastic welcome from the City of Westfield and is a point of pride for the GAI team. “I was on-site when the barricades were removed after construction, and people were itching to drive through it,” said Vorisek. “I remember one resident who spotted us out their car window and said, ‘Great job!’ It was one of those very satisfying projects in which much of the neighborhood was aware of how difficult it had been previously to get onto the main road from the side street, and people were very much looking forward to the roundabout being complete.”

The GAI team provided the City of Westfield with a wide scope of services on the Carey Road/171^st Street roundabout project including topographic survey, design, preparation of construction plans and specifications, assistance during the bidding process, and support throughout the construction phase to address any questions from the city or its construction contractor.

“The City of Westfield was elated with the performance and services performed by the GAI team,” said Nail. “GAI provided a creative solution with a very condensed project development timeline, which helped save the city more than $1M in construction and right-of-way costs. Their communication and responsiveness were second-to-none from start to finish.”

For Jay Vorisek, the Carey Road/171^st Street roundabout offers an ongoing reminder of the local impact of GAI’s work. “I live not too far away, and I drive through this intersection all the time,” he said. “It’s very gratifying to see traffic flowing with minimal interruption while joggers, bicyclists, and pedestrians are able to cross Carey Road safely. It’s almost as if the roundabout itself has generated shared-use traffic because now all users are confident that they can utilize the intersection with ease and safety.”