Neighborhood Study / Traffic Calming

In an effort to enhance residential traffic conditions around the City of Lansing, the Transportation and Parking office has conducted and is continuing to conduct studies in various parts of the city. The status and results of those areas can be viewed through an interacted map provided HERE.

Traffic Calming Measures  

Routine Traffic Control Devices
Installation of Routine Traffic Control Devices are one of the results of the Neighborhood Traffic Study and Traffic Calming Programs. These devices include stop signs, yield signs, and parking controls. 

Stop Signs
Stop Signs are installed at an intersection only after a careful engineering evaluation of the existing conditions indicates that their installation is appropriate. They are used to assign right of way at intersections with limited sight visibility identified through field studies or at high accident locations. Stop signs are not used for speed control or traffic diversion. Overuse of unwarranted stop signs reduces their effectiveness and they are largely ignored by drivers who tend to speed up between stop sign controlled intersections rather than slow down. 

Yield Signs
Yield Signs are installed at an intersection after the same type of engineering evaluation used for stop signs. They are used to improve safety where visibility is somewhat limited or to define right of way for approaching traffic. They have the same safety benefits as stop signs, but are not as restrictive to traffic flow. 

Parking Controls
Parking Controls can directly affect the volume of traffic on residential streets, particularly where these streets are heavily used for parking by commuters, shoppers, and other traffic attracted by nearby non residential destinations. Parking controls can only be effective traffic management devices if the problem traffic is comprised predominantly of outsiders who use the streets for parking. 

Alternating Two-way Stop Controls
Alternating Two-way Stop Controls are considered to be an appropriate traffic calming technique using traditional traffic control devices in specialized cases. They are most effective in older neighborhoods which were designed and constructed in the early to mid 1900's using the grid system for street design. The principal is to stop traffic in alternating directions at adjacent intersections. This creates a condition where traffic can travel two blocks in each direction before encountering a traffic control device. The philosophy is that all streets in the neighborhood are equal in importance. They have the added benefit of creating safer walking routes to and from neighborhood schools and play grounds. 

Geometric Controls
Geometric Controls which are used for neighborhood traffic calming fall into two categories: (1) features which physically restrict and prevent vehicle movement, such as chokers, semi-diverters, neck downs, chicanes, traffic circles, diagonal diverters, forced turn channelization, and cul-de-sacs; and (2) features which physically reduce speed, such as speed humps and raised intersections or crosswalks.  

Choker
A Choker, or curb extension, is the narrowing of a street, either at an intersection or mid-block location, in order to reduce the width of the roadway. When a choker is constructed at an intersection and prohibits a traffic movement, a semi-diverter is created. When a choker is installed in the middle of the block, a neck down is created. When a series of chokers are installed on alternating sides of the street chicanes are created along an extended stretch of road.  

Traffic Circle
A Traffic Circle is a raised island, which is usually landscaped and located at the intersection of two streets. The use of traffic circles is restricted to residential streets. They have been found to be very effective in reducing traffic speeds without diverting traffic to adjacent streets.  

Diagonal Diverters, Cul-de-sacs and Forced Turn Channelization 
Diagonal Diverters, Cul-de-sacs and Forced Turn Channelization are the most restrictive traffic calming devices. A diagonal diverter essentially disconnects two streets at an intersection forcing all traffic to make sharp turns. It makes direct travel through a neighborhood impossible by redirecting all of the traffic. Cul-de-sacs are a complete barrier to traffic at an intersection or in the middle of the block, thus leaving the street open to only local traffic. It is generally difficult to develop an adequate turning radius and retrofitting an existing street can be very expensive. Forced turn channelization is similar in nature to a diagonal diverter, but slightly less restrictive. 

Speed Humps
Speed Humps are raised areas in the pavement surface extending across the roadway. Normally they have a height of 3 to 4 inches and a width of 14 feet with a specially designed profile to cause driver discomfort at speeds greater than the posted speed limit. The speed humps usually cause at least a reduction in traffic volume and have proven to significantly reduce speeds when properly spaced along a stretch of road. Only speed humps, not speed bumps can be installed on city streets.

Raised Intersections are similar to speed humps in speed reduction effectiveness. However, in these situations, the entire intersection is raised 3 to 4 inches with slopes to the adjacent streets. 

Raised Crosswalks 
Raised Crosswalks are also similar to speed humps except that the top is flattened so that it can be used for pedestrian traffic crossing the street. They have the same affect on vehicular speeds, while increasing pedestrian visibility.  

(It should be noted at this point that Rumble Strips have been used in rural areas where vehicular noise is not an issue. They are not appropriate in the dense residential neighborhoods of Lansing due to increased noise.)