Road Management & Engineering Journal
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Although traffic calming seems to [be] becoming more popular lately, it isn't new to Kansas. One Topeka, Ks., neighborhood has traffic-calming devices dating from the late 1800's. The Potwin neighborhood has landscaped circles in some of its intersections to keep vehicles from building up speed and discouraging general traffic from going through their neighborhood. "They're definitely effective," says Lee Holmes, Topeka's city traffic engineer.
But Topeka has not always been successful in getting traffic-calming projects off the ground. Last year, Topeka tried to initiate a pilot project for speed humps in a residential area near a large shopping mall, but the project was stopped due to lack of support from the neighborhood. "In fact," said Holmes, "many people were adamantly against it."
The project included three speed humps set 300 feet apart on a straight stretch of road about 1/8 mile long. The humps were proposed due to complaints from some residents in that neighborhood about vehicles speeding on Brookfield Road.
A traffic study was conducted, showing that the average speed was four miles per hour above the 30 mph speed limit, but the perceived problem was much higher. The goal of the project was to slow traffic back down to the speed limit and perhaps divert some of the traffic away from Brookfield Road.
Although residents wanted calmer traffic, they weren't willing to pay the price--in this case, new signage and restricted on-street parking in front of their homes. The project has been dropped.
Manhattan, Kansas, has had better luck with community support for recent traffic-calming projects. Manhattan is building and planning traffic circles, "chokers," and roundabouts to control traffic speed and address other safety concerns.
Circles. According to Jack Messer, Manhattan's city engineer, the city plans to build 21 traffic-calming circles (three per year) over the next seven years. Traffic circles are raised obstructions placed in the middle of intersections to narrow the travel lanes and interrupt a straight flow of traffic. They are encircled by a raised curb and a truck apron. The size of the circle depends on the width of the roads and what type of fire fighting vehicle that might drive through that intersection, said Messer. As part of the design process, the city sets up a "test run" by placing cones in a circle in the intersection. The diameter is adjusted as necessary as a fire truck attempts to negotiate around the circle.
Circle interiors are either planted with grass or other plants, or they are paved, depending on their size.
The city establishes priorities for where circles will be placed based upon the accident history of an intersection--or street geometry in the case of a new street. A circle might also be considered as part of routine curb and gutter or intersection maintenance project, Messer said.
"In the case of a new subdivision, if there is a long stretch of straight road, we suggest that perhaps we should initiate traffic calming. We don't currently have the means to require that. But we're writing new regulations to require traffic-calming measures when we see that they're necessary. Builders have been very cooperative with us so far, and we don't anticipate anything adversarial, but we'd like to have regulations in place if we should need them."
Messer said traffic-calming circles range in price from about $3,000 for a new street to $4-6,000 for a retrofit in an older area.
Chokers. A choker is a road area that is narrowed by building the curbs out further into the street. "Chokers narrow the street, which causes traffic to slow down, and they help with sight distance problems," said Messer. "You can take a 31 foot wide street and narrow it down to, say, 23 or 24 feet."
The extra space created between the curb and the sidewalk is usually planted with grass.
Chokers are useful if vehicles are parking too close to an intersection. Another benefit is shortening the distance pedestrians have to cross.
Manhattan does not have a specific plan for installing chokers. They are considered as needed and are one of the alternatives offered when residents request measures to control speeding in their neighborhoods.
Chokers cost "no more than removal of concrete plus the curb and gutter work," said Messer.
Roundabouts. Manhattan is currently finishing bid specs for its first roundabout, planned for the intersection of Candlewood Drive and Gary Ave. This is a higher-volume intersection where the city needs to keep traffic moving, but more slowly.
"The intersection is currently a 2-way stop and warrants a 4-way stop, but not a signal," said Messer. "A roundabout appears to be a good solution. It's a mixed intersection, with a commercial business on one corner, a church on another corner, and apartment complexes throughout the area. A major thoroughfare, K-113, feeds into the intersection. And there's an elementary school very close by," Messer said.
Another roundabout being considered in Manhattan, pending approval by the city commission, would be at the intersection of Claflin Road and Manhattan Ave. This is a proposed STP safety project through the Kansas Department of Transportation (KDOT). "We applied for the grant, but KDOT came up with the idea for the roundabout," Messer said. KDOT will participate in the presentation to the city commission scheduled for September 1997. If approved, the project would be constructed sometime in 1999.
Messer's staff has prepared a report for their city commission entitled Neighborhood Traffic Controls. This report is available from the KUTC.