Architecture & Design, Construction, and Travel & Tourism

A roundabout solution to tight traffic congestion

Consulting firm engineers smaller roundabouts to improve limited roadways.

September 9, 2016
| By Pat Evans |
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A lot goes into engineering traffic, an area in which a department at Fishbeck, Thompson, Carr & Huber specializes.

Recently, FTCH’s Chris Wall helped the Washtenaw County Road Commission with a predicament in its traffic management. Wall said the commission’s senior project manager, Mark McCulloch, was attempting to keep vehicle capacity and safety high but was faced with limited funding, tight roadways and high-speed approaches.

“Given the progress of technological advances, traffic engineering is always adapting and evolving,” Wall said. “Yet, the tried-and-true influence of learning from past practices and projects is ever present in traffic engineering.”

The solution, McCullough found, was to take roundabouts and size them for the environment he needed to better serve.

Wall and the FTCH Traffic Engineering Department engineered three compact roundabouts to fit into the areas that needed modifying. The small roundabouts provide the same benefits as larger roundabouts but with less impact and expense, Wall said. The smaller size also makes higher-speed approaches possible, he said. According to the Washtenaw County Road Commission website, a compact roundabout at Ann Arbor-Saline and Textile roads in Lodi Township cost approximately $550,000, as construction started last week.

According to FTCH, approximately 7,500 drivers die each year in the United States at intersections. These urban roundabouts, according to Wall, can facilitate more traffic while experiencing a quarter of the injuries and a tenth of the fatalities. Head-on-collisions are greatly reduced, he said, as all cars move in a counterclockwise traffic flow.

Injuries to pedestrians also are diminished, as they don’t have to look at four directions of oncoming traffic and consider the color of the traffic light, he said.

The compact roundabouts can be built within standard public right-of-ways without purchasing more land or protruding into adjacent land, and the design allows for large trucks and tractors to drive through the roundabout.

FTCH released a detailed report on conventional roundabouts in 2013.

The report suggested comfort as a reason there is reliance to traffic signals and a hesitancy regarding roundabouts. There are more than 300,000 signalized intersections in the country, according to the report.

“We have grown comfortable with a traffic control system governed by automated signals,” the report read. “We motorists don’t even necessarily have to think that much, we just react; an increasingly dangerous proposition, as our roads fill with ever more passive and distracted drivers.”

The report suggests roundabouts engage drivers, leading to more awareness than a conventional intersection. Also among the benefits listed was no delay because of a red light when no other motorist is at the intersection and fewer vehicle emissions.

Wall said the FTCH Traffic Engineering Department works with both private and public clients, often performing and aggregating counts of motorized and non-motorized traffic for use in studies and analysis. The department also determines operation conditions of existing road facilities, he said.

The duties of the department also look at testing alternatives to improve roads, designing intersection and pedestrian crossing signals and planning traffic through construction zones, Wall said.

While the Washtenaw County intersections needed to look at the past for a solution and the fitting of a smaller roundabout, Wall said technology is changing the way traffic is engineered.

Among the chief advancements in traffic technology include the use of cellphone data for real-time traffic input and feedback, such as congestion and crashes, advisories and route modifications, Wall said.

“The unique and exciting part of traffic engineering is it covers a wide-spread (area) of engineering and project types. In one instance, you could be assessing circulation in a parking structure and, the next minute, instructing the public on how to navigate a roundabout,” Wall said.

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