Urban landscaping in the 20th century focused on the quick and unobstructed flow of motor vehicle traffic. It is only within the last few decades that urban planning has started to embrace more balanced spaces within the community—encouraging walking, cycling, and outdoor social interaction. This innovation of shared space calls for traffic calming strategies that help to create safer streets for everyone.
What is traffic calming?
Traffic calming is a road design strategy that promotes attentive and responsible driving. It uses sensory-rich environments to reduce vehicle speeds and foster safe habits among all road users.
Why does it work? Traffic calming design forces drivers to pay attention to their overall driving environment to determine their driving behavior. Factors such as road conditions, obstructions, sight distance, and the presence of pedestrians can seriously impact road safety. Traffic calming strategies are used to create environments where the most convenient driving behaviors are also the safest.
Modified streetscapes can help achieve a range of community goals—both functional and aesthetic—for the benefit of all street users. Traffic calming is especially valuable in areas with high pedestrian activity—crowded downtown streets, commercial districts, mixed-use spaces, recreational streets/boulevards, and areas surrounding transportation hubs.
When implemented effectively, traffic calming provides many positive outcomes:
- Safer streets for pedestrians and cyclists
- Reduced traffic noise
- Increased local economic activity
- Increased universal access
- City beautification and revitalization
Traffic calming strategies include adjusting lane width, as well as using roundabouts, medians, diverters, and vertical deflections. Bollards also play a significant role in each of these traffic calming initiatives by improving their overall effectiveness.
One basic way to encourage slower driving is to reduce lane widths. Narrow lanes require more concentration and accurate steering. The simplest way to narrow traffic lanes is to move pavement markings. Roads can also be physically altered, creating opportunities for wider sidewalks and lanes for bikes or public transit.
Sidewalk extensions can be used to provide space for amenities such as benches, trees, street lighting, and kiosks. When used to contain parking bays, extension angles will affect vehicle access. Sharp angles require parallel parking, while shallow angles accommodate back-in spaces.
Neckdowns are a popular form of road narrowing. A neckdown, also referred to as chokers or bulbs, can be installed at intersections or mid-block. Neckdowns are often used to define roadside parking bays—parallel or diagonal. They also reduce the distance for foot traffic crossing streets.
Chicanes are neckdowns installed in series—alternating along either side of a street—forcing vehicles to slalom between each extension. They work best with narrow lanes to prevent vehicles from cutting corners. Small medians can also be placed at intervals within chicanes to prevent vehicles from entering oncoming lanes.
Much like narrow lanes and neckdowns, corners can be modified at intersections to create tight radii for vehicles. This forces vehicles to slow down to avoid traversing curbs or losing control. Tight corners, however, can be difficult for long vehicles and/or trailers to navigate.
Bollards and lane adjustments
Bollards offer clear visual elements that alert drivers to changes in lane patterns. Bollards are designed to sit at an ideal height for driver visibility while preserving safe fields of vision and long sightlines. Bollards can also be installed with security reinforcement to withstand vehicle impacts, ensuring protection for pedestrians and valuable street elements.
Flexible bollards can be used in conjunction with narrow lane markings. They retain the visibility advantage of traditional bollards, while avoiding any damage to vehicles and surrounding pavement in case of a collision.
Roundabouts and traffic circles
Roundabouts and traffic circles are round islands installed in the middle of intersections to prevent straight-through traffic. They encourage steady, regulated flow—minimizing the start-stop patterns of traditional intersections. In terms of physical design, roundabouts do not require traffic lights. However, proper signage is important. Entry lanes can be installed to guide traffic into roundabouts.
Typically, roundabouts feature only a single lane—and rarely more than two—to prevent confusion among drivers. Traffic circles can be designed with sloped perimeters to reduce obstruction of long emergency vehicles and buses. They can be installed to accommodate a range of traffic scenarios and neighborhoods. However, unless significant space is available, they should be avoided in high-traffic arterial streets. For low-traffic intersections with available space, roundabouts can accommodate pedestrian crossings and amenity features such as statues, fountains, and community gardens.
Bollards and roundabouts
Roundabouts often feature public art and landscape installations. Bollards can offer complementary design aesthetics while also protecting community assets. For traffic circles with regular foot traffic, bollards protect pedestrians by preventing vehicle access.
Medians and boulevards
Medians and boulevards occupy middle areas along roads, separating opposing lanes from oncoming traffic. They can be used to reduce lane widths and are typically cheaper to install than extending sidewalks.
Medians provide a pedestrian refuge amidst busy, multi-lane roads and offer a natural barrier to prevent drivers from making U-turns. Medians can be installed with fences to prevent pedestrians from crossing at unsafe areas. They can also be landscaped with gardens or furnished with amenities and city art. As part of a larger traffic management plan, medians can also restrict the direction of traffic at intersections.
Bollards and medians
Medians offer prime opportunities to regulate vehicle and pedestrian traffic. Bollards manage pedestrian flow when used in combination with continuous barriers—such as fences or dense landscape elements—creating safe-passage for pedestrians while preventing vehicle access.
Diverters are physical barriers used to redirect traffic and are especially useful in residential areas. Diverters can be designed to accommodate passage for pedestrians and cyclists, and can incorporate decorative aspects such as greenery, lighting, and other site furnishings.
Diverters create significant disruptions to traffic flow, and should be used as part of a more comprehensive traffic management plan. Without proper planning, diverters can cause spillover traffic into nearby areas and may disrupt response times for emergency vehicles.
There are a range of diverter types that can be used for different configurations. They are typically installed at, or around, intersections.
- Diagonal barriers
Installed to traverse intersections to create two disconnected streets that turn away from each other.
Restricts traffic flow in one direction, typically blocking road access from arterial streets into residential areas.
- Full diversions
Completely blocks access between arterial streets and quieter neighborhoods—often using cul-de-sacs to allow vehicle turnarounds in isolated streets.
Bollards and diverters
Diverters often connect or extend pedestrian areas. They are especially useful in residential areas with high amounts of foot traffic. Bollards help ensure effective through-ways for pedestrians while reinforcing vehicle barriers. Decorative bollard designs ensure that the aesthetics complement the character of surrounding neighborhoods.
Vertical deflections and surface treatments
Vertical deflections include all forms of speed bumps, speed humps, speed cushions, and speed tables. Like other forms of traffic calming, vertical deflections offer passive enforcement. They are visual and physical cues to drivers, encouraging them to slow down to an appropriate speed. Drivers who ignore these deflections risk severe discomfort and potential damage to their vehicles.
The shape and size of deflections affect vehicle speeds. Large bumps with steep inclines are more disruptive, while small bumps with shallower deflections are less intrusive. Speed bumps are typically the most intrusive intervention for vehicles—while speed humps, speed cushions and speed tables create milder disruptions. Deflections can be formed using concrete or asphalt. Preformed, bolt-down products are also available for easy and consistent installation.
Surface treatments also slow vehicles. Rumble strips are common interventions that offer tactile cues, encouraging drivers to reduce speeds to avoid significant vibrations. They also provide visual cues, which can be used to identify crosswalks. Surface treatments can be installed in series across road surfaces to slow vehicles over a larger area, or alert drivers entering sensitive areas. Prefabricated rumble strips can be installed in pavement, but various forms of cobblestones and pavers are also common.
Bollards and vertical deflection and surface treatments
Bollards can be used to prevent vehicles from circumventing obstructions, and clearly identify them to drivers. Surface treatments are ideal in areas surrounding crosswalks—where bollards can identify and protect pedestrian waiting areas—especially around curb extensions.
Traffic bollards have a strong role to play in enhancing many of the most common and effective traffic designs. Aside from improving safety, bollards are designed to regulate interactions between vehicles, pedestrians, and other forms of traffic.
A range of bollard styles are available to complement surrounding street and building designs—offering a better sense of place for local residents and commercial visitors.
Traffic Calming: Moving Beyond the Automobile
Traffic calming strategies keep cities safe for pedestrians, cyclists, and motorists. Watch the video to see how a few major cities in the Unites States implemented traffic calming infrastructure to reduce accidents.
- Project for Public Spaces. "Traffic Calming 101".
- Transportation Demand Management Encyclopedia. "Traffic Calming Roadway Design to Reduce Speeds and Volumes". Victoria Transport Policy Institute.