The roundabout — about half the size of the one in Towson — will replace the traffic lights at the gateway intersection that connects South Baltimore and the Inner Harbor near the Maryland Science Center. Construction could begin as soon as July.
The intersection has long been a malfunction junction, with befuddled motorists and daredevil pedestrians mixing it up on a road surface scarred by old streetcar tracks.
"No doubt there's confusion about how to get to Federal Hill and how to stay on Key Highway. People are making left turns from the right lane. You take your life in your hands trying to cross the street," said Ryan Hada, president of the Federal Hill Neighborhood Association.
At the urging of community leaders, the city looked at several alternatives, ranging from an upgrading of signs and lighting to a full reconstruction of the intersection. Officials chose the roundabout route for its function and aesthetics.
"The roundabout slows traffic and focuses drivers' attention to be looking for vehicles coming from one direction. Motorists entering the roundabout yield to vehicles already in it and that limits the number of potential conflicts," said Jim Harkness, deputy chief of traffic for the Baltimore Department of Transportation.
The intersection upgrade also is expected to curtail the mad dash by pedestrians across multiple lanes of traffic.
"The road leading into the roundabout will have a physical barrier in the middle — called a splitter island — so that pedestrians will have to cross just one-half of the road at a time," Harkness said. "Sight lines will be better and signage will alert motorists to the presence of pedestrians."
The final design of the roundabout's inner circle has yet to be determined, but early drawings include native grasses and flowering shrubs with local artwork or a fountain at the center, making it "an iconic and unique landmark," said department spokeswoman Adrienne Barnes.
Hada called the roundabout "pleasing to the eye and a gateway to the community."
But, he said, city engineers must prove it will be effective.
"I think the neighborhood will be supportive if it provides for pedestrian safety, if there's efficiency in the flow of traffic and if it ultimately slows traffic," he said. "They have to show us conclusive evidence that it will."
A study by the Insurance Institute for Highway Safety of 24 intersections where a roundabout replaced traffic lights or stop signs found that overall crashes decreased by 75 percent while pedestrian injuries dropped by 40 percent.
Engineers anticipate vehicles approaching the roundabout will have a top speed of 15 mph. A pedestrian-activated traffic light will be added at William Street and Key Highway, a major crosswalk between Federal Hill and the Inner Harbor and a bike crossing for the Gwynns Falls Trail. The bone-jarring tracks will be removed.
Even though the Baltimore Grand Prix route stops a block short of the intersection, the construction timetable and specifications will be written to ensure there is no disruption to either activity, Harkness said.
Once considered an oddity, roundabouts have become a go-to tool for state transportation planners since the first one was constructed in Howard County in 1993. Maryland is No. 3 in the nation, behind only Colorado and Florida for the number of roundabouts, according to federal highway statistics.
The Key Highway intersection is estimated to handle about 8,000 vehicles daily. By contrast, the Towson roundabout, which opened in 1998, serves more than 47,000 vehicles a day and the much-smaller West Street roundabout in Annapolis handles 24,000 vehicles.
Harkness said motorists these days have had plenty of practice with roundabouts and while they might be a little leery of the new setup at Key Highway, they quickly will adapt.
City officials expect to hold public meetings next year on the final design.