Reclaiming City Streets


The Benefits of Low Speed Zones and How to Effectively Design One

Low speed zones can greatly improve road safety, especially in densely populated urban areas. By reducing vehicle speeds to 20 mph or below, these zones have been proven to reduce the number and severity of crashes. For city planners and policymakers, implementing an effective low speed zone requires careful planning and design.

Why Low Speed Zones Matter

There are several reasons why low speed zones should be a key part of any comprehensive vision for urban road safety:

They reduce vehicle speeds. Lower speeds give drivers more time to react to hazards and bring vehicles to a stop. At 20 mph, stopping distances are half that of 30 mph. This extra reaction time is crucial in busy areas with pedestrians, cyclists and intersections.

They prevent serious injuries and fatalities. Research shows that pedestrians struck by a vehicle at 20 mph have a 95% chance of survival. But increase the impact speed to 30 mph and the chance of death rises to 55%. Lower speeds dramatically reduce crash severity.

They encourage non-motorized transport. Streets with slower speeds feel safer and more welcoming to people walking and biking. This promotes active mobility and reductions in emissions.

They create vibrant public spaces. Slower streets facilitate social interactions, outdoor commerce and placemaking.Spaces feel more human-centered than vehicle-centered.

They improve equity and access. Lower speed zones extend the benefits of safe mobility to all road users, especially the most vulnerable like children and the elderly. They ensure access for entire communities.

For these reasons, low speed zones should be part of any 21st century vision for sustainable, just and people-oriented cities.

Designing Effective Low Speed Zones

However, simply installing a 20 mph speed limit sign is not enough. Effective low speed zones require holistic planning and design tailored to local contexts. Here are some key steps:

Conduct speed and volume studies. Use data to analyze current vehicle speeds, volumes and crash rates on potential zone streets. This establishes baselines.

Select zone boundaries. Determine which streets to include based on factors like land use, crash data, traffic volumes and presence of vulnerable users. Focus first on busy pedestrian areas.

Use traffic calming elements. Narrow lanes, speed humps, chicanes, raised crosswalks and other physical elements help reduce speeds. Apply self-enforcing measures so limits are obeyed without police presence.

Improve infrastructure for non-motorized users. Widen sidewalks, add bike lanes, upgrade crosswalks and improve intersection markings to encourage walking, cycling and public transport use.

Educate residents. Communicate with residents and stakeholders on the benefits of lower speeds and the need to change behaviors. Garner community buy-in before implementation.

Enforce new limits. Police should initially focus on information campaigns, not strict enforcement. Fines can come later for those who flout the law. Automated speed cameras also help with enforcement.

Evaluate and iterate. Collect before-and-after data on speeds, traffic volumes and crashes. Identify issues and adjust designs. Low speed zones require ongoing management.

Design Elements to Reduce Speeds

There are many design elements transportation planners can use to self-enforce lower speeds in zones. Key options include:

Lane Narrowing

Lane widths of 3.25 meters encourage lower speeds by visually narrowing the road for drivers. Narrower lanes are also safer for cyclists. Reduce lane widths by reallocating space to sidewalks, bike lanes or landscaping.

Speed Humps, Tables and Cushions

Vertical traffic calming devices like humps, tables and cushions cause discomfort for drivers exceeding the speed limit. Their raised profiles force motorists to slow down.


Chicanes are a series of raised or delineated curb extensions that alternate from one side of the street to the other. This requires vehicles to zig-zag, reducing speeds.


Multi-lane roundabouts interrupt traffic flow and eliminate high-speed left turns. Well-designed roundabouts reduce crashes by 75 percent at intersections.

Raised Pedestrian Crossings

Elevating crosswalks to sidewalk level or using speed tables at crossings forces approaching drivers to slow down. This improves yielding behavior.

Reduced Turning Radii

Tighter turning radii at intersections shorten crossing distances for pedestrians. This encourages slower turning speeds from motorists.

Textured Paving

Using textured materials like stamped asphalt or concrete for the roadway introduces vibration and friction that compels speed reductions.


Entry treatments like reduced road widths, landscaping and “gateway” signage notify drivers that they are entering a low speed zone. This triggers speed adjustments.

Additional Measures to Support Safety

Beyond speed reduction treatments, some supplementary measures can bolster safety and optimize low speed zone performance:

Upgrade crosswalks. Use high visibility continental or ladder style markings. Introduce lighting and medians for pedestrian refuges.

Improve signage. Ensure speed limits, warnings and regulations are clearly visible. Use variable message and in-street signs to alert drivers.

Prioritize active mobility. Introduce bike boulevards, bike boxes and intersections with bike/pedestrian priority. Enable safe mobility for all.

Enhance streetscapes. Incorporate greening like trees, planters and rain gardens. Create an environment conducive to lower speeds.

Adjust traffic signals. Review signal timing to ensure smooth traffic flow at slower zone speeds. Prioritize pedestrians at crossings.

Provide alternative routes. Use traffic diversions, turn prohibitions and truck restrictions to reduce through traffic on zone streets.

Limit on-street parking. Eliminate or consolidate parking spaces to gain space for other active mobility uses. Manage parking supply.

Improve lighting. Ensure roads and sidewalks are well-lit for safer nighttime walking and cycling. Use smart LEDs on pedestrian-scale poles.

Key Placement Considerations

Equally important as road design is where low speed zones are instituted. Some prime locations include:

City centers: High density downtowns and commercial districts with heavy foot and cycle traffic.

School zones: Streets near elementary, middle and high schools. Children deserve safe routes.

Parks and recreation centers: Roads bordering playgrounds, sports facilities and other community hubs with families present.

Retail and restaurant districts: Entertainment areas and commercial zones, especially those with outdoor dining.

Residential neighborhoods: Local and collector roads lined with homes, apartments and shops. Where people live and interact.

Near public transport: Bus stops, transit stations and hubs. Enable safe access with lower speeds.

Communicating the Benefits to the Public

For low speed zones to gain community support, the many benefits must be clearly communicated. Some key messages to emphasize include:

  • Improved safety and crash reduction, especially for vulnerable groups like children and the elderly. Accidents fall significantly.
  • Inviting, human-centered streets that encourage walkability, cycling and public transport use. Streets become destinations, not just conduits for cars.
  • Cleaner air and lower transport emissions due to less vehicular travel. Supports sustainability and quality of life.
  • More cohesive communities where residents interact comfortably. Lower speeds foster social connections.
  • Healthier lifestyles with more active mobility. Walking and biking rates increase.
  • More equitable access for all road users. Speed reduction enables mobility for everyone.
  • Vibrant local economies and commerce. Slower streets feel welcoming to businesses and customers.
  • Calmed traffic and less cut-through driving. Less vehicle noise and intrusion on neighborhoods.
  • Cities reclaimed for people, not cars. Streets become community spaces, not speedways.

Overcoming Potential Opposition

While low speed zones enjoy wide public support, some opposition may occur. Concerns typically include:

Longer trip times: Some drivers feel lower speeds unfairly increase travel times. But the time penalty is usually small, while safety benefits are large.

Less “traffic calming”: Those wanting more extensive road redesigns may view just lowering the speed limit as insufficient. But lower limits still markedly improve safety.

Compliance and enforcement: There is skepticism about voluntary compliance. But designing self-enforcing streets and education campaigns foster adherence. Data shows most drivers obey new lower limits.

Emergency vehicle access: Some worry lower speeds hinder fire trucks and ambulances. But many features like speed humps are designed to exempt emergency vehicles. Proper traffic diversion also manages access.

Diversion to other streets: Limiting cut-through traffic requires balancing vehicle flows across the road network. Traffic studies and diversions can manage this.

Loss of on-street parking: While lower limits don’t ban parking, some cities consolidate spaces for pedestrian and cycle facilities. This requires political finesse.

Cost: While physical traffic calming entails expense, lower speed limits alone are cheap. And preventing injuries and deaths has major economic benefits that outweigh costs.

Lack of public awareness: Efforts to educate residents and share accurate data on benefits are key to securing support and easing concerns. Communication is vital.

Starting the Process in Your City

For city leaders and staff looking to implement lower speed zones, here are some steps to kick off the process:

Establish goals. Set clear targets for expanding 20 mph zones by a certain area, percentage of roads or reduction in severe injuries. This drives strategy.

Assess current conditions. Collect data on vehicle speeds, volumes, crash rates and cite concerns. Develop heat maps showing high-risk areas in need of intervention.

Review best practices. Examine lessons from other cities successfully using speed reduction zones. Adapt proven approaches to your context.

Identify priority zones. Use crash data, traffic patterns and vulnerable user locations to determine initial focus areas for new 20 mph zones.

Engage stakeholders. Set up outreach processes to gather input from community groups, businesses, transport agencies and emergency services. Address concerns.

Develop timeline and budget. Create a phased plan with specific milestones and costs. Consider quick wins like school zones. Identify funding sources.

Revise policies. Update speed limit-setting criteria. Allow lower limits near pedestrian generators without traffic calming. Empower action.

Leverage partnerships. Coordinate with police on enforcement needs. Collaborate with schools and hospitals on zone locations. Use synergies.

Enact legislation. Pass city ordinances authorizing expanded 20 mph zones. Provide legal foundation for broad implementation.

Monitor and evaluate. After new zones are installed, collect follow-up data on speeds, crashes and usage. Gauge effectiveness and modify approaches.

Joining the Global Movement to 20 mph

Cities across the world are embracing 20 mph limits as a new norm for urban street safety. London, Barcelona, Boston, New York and Toronto are just some of the major cities setting maximum speed limits of 20 mph. It is an important strategy to achieve Vision Zero goals where no one dies or suffers serious injury on roads.

Transportation leaders must respond aggressively to rising pedestrian and cyclist fatalities. Lower urban speed limits are a proven, effective policy lever. They make streets significantly safer for all users, especially the most vulnerable.

Cities have an obligation to enable safe mobility for all residents between their homes, schools, shops, workplaces and parks. Lower speed zones are a key part of fulfilling that responsibility. They allow roads to be shared safely by everyone – motorists, cyclists and pedestrians alike.

Streets are vital community spaces, the connective tissue of urban life. They must be designed first and foremost for people, not vehicles. 20 mph speed limits rebalance streets to make them more equitable, healthy and livable. It’s time to usher in a new era of slower, safer and more sustainable cities.

The Time is Now for 20 MPH Speed Limits

Around the world, forward-thinking cities are embracing 20 mph or 30 km/h speed limits as a new standard for urban streets. From London to Boston, Barcelona to Toronto, cities are recognizing the vast benefits that lower speed zones provide. It is part of a growing movement to prioritize safety and make streets more equitable for all users. City leaders everywhere should take note and quicken the adoption of 20 mph limits.

The reasons are clear. Extensive research verifies that lower urban speed limits save lives, prevent injuries, promote active transport, spur community cohesion and create more vibrant, livable cities. 20 mph zones are a proven, evidence-based policy intervention that achieves multiple goals at once. They are a keystone strategy for any Vision Zero or sustainable mobility plan.

The design principles are well established too. Effective 20 mph zones require holistic planning with self-enforcing physical and visual cues built into streetscapes themselves. Signs alone are not enough. Elements like narrowed lanes, speed humps, chicanes, enhanced crosswalks, landscaping, prominent signage and gateways consciously slow motor vehicle traffic. Streets must be engineered for slower speeds.

Additionally, low speed zones should focus first on areas with the highest foot and cycle traffic and greatest interaction between motorists and vulnerable road users. City centers, schools, parks, shops and transit hubs warrant prime attention. However, 20 mph limits can benefit all urban neighborhoods. Broad implementation creates a safer speed norm.

Cities must couple appropriate design with education, community engagement and some enforcement to maximize adherence. Communications should emphasize safety benefits while addressing concerns about diversion and parking impacts. With self-enforcing streets and public awareness, most drivers will modify their behavior within low speed zones. This culture shift takes time but is achievable.

In the journey to safer city streets, reducing traffic speeds is the single most effective intervention. It mitigates the worst impacts when collisions happen. This allows mobility for all while prioritizing the most vulnerable users. Done right, 20 mph zones exemplify the ethos of shared streets and the ethic of caring for others. They enable mobility justice.

City dwellers worldwide should unite in demanding this action from their leaders and policymakers. The state of road safety globally is unconscionable. We must stem the toll of 1.3 million annual traffic fatalities. 20 mph limits work and are within our grasp. Vision Zero is only possible with slower urban traffic speeds.

The benefits vastly outweigh the costs. Investing now in lower speed zones will save lives immediately, while making cities healthier and more sustainable for generations to come. This is our responsibility to today’s residents and future citizens.

Fundamentally, 20 mph speed limits recognize the appropriate role of cars in communities. Streets should not primarily be conduits for maximizing vehicular mobility and throughput. Their highest purpose is allowing access and participation in community life. Lower speeds transform roads into shared public spaces for social interaction and economic exchange. Streets become places again, not just travelways.

The time is now for global uptake of 20 mph limits. We have the knowledge and tools. Cities must bring the same boldness and urgency seen in response to COVID, climate change and social justice. Passionate advocacy is required. With courage and commitment, urban leaders can redesign streets to be safer for all. Let us find inspiration in the progress made so far and rapidly accelerate action. The movement for 20 mph has reached an inflection point. We know what needs to be done.

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