Curb Extensions
Chokers
Crossing Islands
Chicanes
Mini-Circles
Speed Humps & Speed Tables
Raised Intersections & Raised Crosswalks
Gateways
Landscaping
Specific Paving Treatments
Serpentine Design
Woonerf
Learn More About Traffic Calming Techniques

Dan Burden, www.walkinginfo.org

Curb Extensions Curb extensions - also known as bulb-outs or neckdowns - extend the sidewalk or curb line out into the parking lane, effectively reducing the width of the street. By reducing street width, curb extensions reduce the distance a pedestrian must cross to get across the street and reduce the amount of time pedestrians are in the street. They also prevent motorists from parking or driving too close to a crosswalk, encourage drivers to travel more slowly at intersections or midblock. It should be noted that curb extensions only work where there is an on-street parking lane. Curb extensions... Improve safety for pedestrians and motorists at intersections. Increase visibility and reduce speed of turning vehicles. Encourage pedestrians to cross at designated locations. Prevent motor vehicles from parking at corners. Shorten crossing distance and reduce pedestrian exposure. Can only be used where there is an on-street parking lane. Can cost anywhere between $2,000 and $20,000 per corner, depending on design and site conditions.

Dan Burden, www.walkinginfo.org

Chokers Chokers are curb extensions that narrow a street by widening the sidewalks or planting strips, creating a pinch point along the street. Chokers can be created by bringing both curbs in, or they can be done by more dramatically widening one side at a midblock location. They can also be used at intersections, creating a gateway effect when entering a street. They can have a dramatic effect by reducing a two-lane street to one lane at the choker point, forcing motorists to slow down or stop as they yield to each other. Chokers... Slow vehicles at a mid-point along the street. Create a clear transition between a commercial and a residential area. Narrow overly wide intersections and midblock areas of streets. Add room along the sidewalk or planting strip for landscaping or street furniture. Usually only appropriate for low-volume, low-speed streets Can cost anywhere between $5,000 and $20,000.

Dan Burden, www.walkinginfo.org

Crossing Islands Crossing islands, or center islands, are raised areas placed in the center of the street at intersections or midblock to help protect crossing pedestrians from motor vehicles. Center crossing islands allow pedestrians to deal with only one direction of traffic at a time, and they enable them to stop partway across the street and wait for an adequate gap in traffic before crossing the second half of the street. Crossing islands have been demonstrated to significantly decrease the percentage of pedestrian crashes. Crossing islands... Enhance pedestrian crossings, particularly at unsignalized crossing points. Reduce vehicle speeds approaching pedestrian crossings. Highlight pedestrian crossings. Can cost anywhere between $4,000 and $30,000.

Peter Lagerwey, www.walkinginfo.org

Chicanes Chicanes create a horizontal diversion of traffic and can be gentler or more restrictive depending on the design. Shifting a travel lane has an effect on speeds as long as the taper is not so gradual that motorists can maintain speeds. Shifts in travelways can be created by shifting parking from one side to the other (if there is only space for one side of parking) or by building landscaped islands (islands can also effectively supplement the parking shift). Chicanes... Reduce vehicle speeds. Add more green (landscaping) to a street. Can cost anywhere between $10,000 and $30,000.

Dan Burden, www.walkinginfo.org

Mini-Circles Mini-circles are raised circular islands built in the center of residential street intersections (generally not intended for use where one or both streets are arterial streets). They reduce vehicle speeds by forcing motorists to maneuver around them. Mini-circles have been found to reduce motor vehicle crashes by an average of 90 percent in Seattle, WA. Mini-circles are commonly landscaped. Mini-circles are an intersection improvement as well as a traffic-calming device and can take the place of a signal or four-way stop sign. Mini-Circles... Manage traffic at intersections where volumes do not warrant a stop sign or a signal. Reduce crash problems at the intersection of two local streets. Reduce vehicle speeds at the intersection. Cost between $6,000 and $12,000.

Dan Burden, www.walkinginfo.org

Speed Hump & Speed Tables Speed humps are paved, generally 3 to 4 inches high at their center, and extend the full width of the street with height tapering near the drain gutter to allow for easy bicycle travel. There are several designs for speed humps. The traditional 12-foot hump has a design speed of 15 to 20 mph, a 14-foot hump a few miles per hour higher, and a 22-foot hump has a design speed of 25 to 30 mph. The longer humps are much gentler for larger vehicles. A "speed table" is basically a very long and broad speed hump or a flat-topped speed hump. Sometimes pedestrians can cross over the flat portion of the speed table. The speed table can either be parabolic, making it more like a speed hump, or trapezoidal, which is used more frequently in Europe. Speed humps & speed tables... Reduce vehicle speeds. Raised measures tend to have the most predictable speed reduction impacts. Enhance the pedestrian environment at pedestrian crossings. Should not be used at sharp curves or steep slopes. Cost approximately $1,000 for speed humps; between $2,000 and $15,000 for speed tables.

Cara Seiderman, www.walkinginfo.org

Raised Intersections & Raised Crosswalks A raised intersection is essentially a speed table for the entire intersection. Construction involves providing ramps on each vehicle approach, which elevates the entire intersection to the level of the sidewalk. They can be built with a variety of materials, including asphalt, concrete, stamped concrete, or pavers. The crosswalks on each approach are also elevated as part of the treatment to enable pedestrians to cross the road at the same level as the sidewalk, eliminating the need for curb ramps. Use detectable warnings to mark the boundary between the sidewalk and the street. A raised pedestrian crossing is also essentially a speed table, with a flat portion the width of a crosswalk, usually 10 to 15 feet. Raised intersections and crosswalks encourage motorists to yield. On one street in Cambridge, MA, motorists yielding to pedestrians crossing at the raised devices went from approximately 10 percent before installation of the project to 55 percent after installation. Raised intersections & raised crosswalksŠ Reduce vehicle speeds. Raised measures tend to have the most predictable speed reduction impacts. Enhance the pedestrian environment at pedestrian crossings. Should not be used at sharp curves or steep slopes. Cost is highly dependent on the size of the road; raised crosswalks are approximately $2,000 to $15,000, and raised intersections can cost from $25,000 to $75,000.

Dan Burden, www.walkinginfo.org

Gateways A gateway is a physical or geometric landmark that indicates a change in environment from a higher speed arterial or collector road to a lower speed residential or commercial district. They often place a higher emphasis on aesthetics and are frequently used to identify neighborhood and commercial areas within a larger urban setting. Gateways may be a combination of street narrowing, medians, signing, archways, roundabouts, or other identifiable feature. Gateways should send a clear message to motorists that they have reached a specific place and must reduce speeds. This can help achieve the goal of meeting expectations and preparing motorists for a different driving environment. Gateways are meant to be an introduction and slower speeds on the rest of the street need to be maintained using other traffic-calming features. Gateways... Create an expectation for motorists to drive more slowly and watch for pedestrians when entering a commercial, business, or residential district from a higher speed roadway. Create a unique image for an area. Cost varies widely depending on the measures chosen.

Dan Burden, www.walkinginfo.org

Landscaping Landscaping can provide a separation between motorists and pedestrians, reduce the visual width of the roadway (which can help to reduce vehicle speeds), and provide a more pleasant street environment. Landscaping techniques can include trees, bushes, and/or flowerpots, which can be planted in the buffer area between the sidewalk or walkway and the street. The most significant issue with any landscaping scheme is ongoing maintenance. Some communities have managed effectively by creating homeowners associations to pay for landscape maintenance or through the volunteer efforts of neighbors. Others have found them to be unreliable and budget for public maintenance instead. Choosing appropriate plants, providing adequate space for maturation, and preparing the ground can help ensure that they survive with minimal maintenance, and don't buckle the sidewalks as they mature. Plants should be adapted to the local climate and fit the character of the surrounding area, they should survive without protection or intensive irrigation; and plant's growth patterns should not obscure signs or pedestrians' and motorists' views of each other. Landscaping... Enhances the street environment. Calms traffic by creating a visual narrowing of the roadway. Must be maintained, either by the municipality or area residents. Are often easier to implement and more affordable than other traffic calming techniques.

Cara Seiderman, www.walkinginfo.org

Paving Treatments Paving materials are important to the function and look of a street, both in the road and on the sidewalk. Occasionally, paving materials in and of themselves act as a traffic-calming device (e.g., when the street is paved in brick or cobblestone). However, some of these materials may be noisy and unfriendly to bicyclists, pedestrians, wheelchairs, or snowplows. Concrete is often chosen as the preferred walking surface; a different look can be achieved by using stamped concrete or concrete pavers, which are available in a variety of colors and shapes. Colored paving can often enhance the function of portions of the roadway, such as a colored bicycle lane. This can create the perception of street narrowing, in addition to enhancing the travel facility for bicyclists. Paving treatments... Send a visual cue about the function of a street. Create an aesthetic enhancement of a street. Delineate separate space for pedestrians or bicyclists.

Cara Seiderman, www.walkinginfo.org

Serpentine Design Serpentine design refers to the use of a winding street pattern with built-in visual enhancements through a neighborhood, which allow for movement while forcing vehicles to slow down. The opportunities for significant landscaping can be used to create a park-like atmosphere. Such designs are usually implemented with construction of a new neighborhood street or during reconstruction of an existing street corridor. This type of design can be more expensive than other traffic-calming options and needs to be coordinated with driveway access. Where costs are a concern, lower cost, equally effective traffic-calming strategies may be preferable. Serpentine design... Can change to the entire look of a street to send a message to drivers that the road is not for fast driving. Can be expensive ($60,000 to $90,000 per block) to retrofit a street, but may be no extra cost to build a new street with this design if adequate right-of-way is available. Is most cost-effective when built as a new street or where a street will soon undergo major reconstruction for utility or other purposes.

Dan Burden, www.walkinginfo.org

Woonerf "Woonerf" ("Street for living") is a Dutch term for a common space shared by pedestrians, bicyclists, and low-speed motor vehicles. They are typically narrow streets without curbs and sidewalks, and vehicles are slowed by placing trees, planters, parking areas, and other obstacles in the street. Motorists become the intruders and must travel at very low speeds below 10 mph. This makes a street available for public use that is essentially only intended for local residents. A woonerf identification sign is placed at each street entrance. Woonerfs... Create a very low automobile volume, primarily on local access streets. Create a public space for social and possibly commercial activities and play by area children. Is generally not appropriate where there is a need to provide nonresident motorists with access to services or through travel. Need to keep vehicle speeds very low in order to make the streets safe for children. Can be expensive to retrofit, but require no additional cost if designed into the original street construction.