Traffic Calming Measures

What Are Traffic Calming Measures?

Traffic calming measures are physical and operational design strategies that reduce speeds, discourage cut-through traffic, and create safer, more comfortable streets for people walking, biking, rolling, taking transit, and driving. Typical tools include speed humps, speed cushions, raised crosswalks, mini-roundabouts, curb extensions (bulb-outs), chicanes, road diets, median islands, and gateway treatments. Together, these elements reshape driver expectations, narrow visual fields, and add vertical/deflection cues so the desired speed becomes the natural speed.

This guide is a practitioner-ready, SEO-focused overview designed for civil and transportation engineers, planners, and public-works teams. It explains how the measures work, when to use them, how to site and space them, and how to evaluate benefits such as injury crash reduction, speed compliance, and crossing comfort. You’ll also find tips for engaging neighborhoods, funding projects, and documenting results for council approvals.

Goal: self-enforcing streets where operating speed matches context, not just the posted sign.

Core Principles of Effective Traffic Calming

• Speed management first: Kinetic energy rises with the square of speed; even small reductions have outsize safety benefits.
• Predictable deflection: Horizontal/vertical shifts (chicanes, mini-roundabouts, humps) are more reliable than signs alone.
• Context sensitivity: Match tools to street function, transit routes, emergency access, grades, and drainage.
• Spacing & sequence: Design as a system—gateways + mid-block features + crossing upgrades—not one-offs.
• Multimodal visibility: Shorter crossing distances, daylighting, and raised elements improve yielding and compliance.
• Measure, iterate, maintain: Use before/after data; adjust spacing or profiles; plan for snow, sweeping, and resurfacing.

Speed Management Measures (Vertical & Horizontal)

These devices directly influence operating speeds by introducing vertical displacement or horizontal curvature. Choose profiles that meet transit and fire department needs while delivering measurable reductions in 85th-percentile speed.

• Speed humps (parabolic or circular): 3–4 in height, 12–14 ft length; typical spacing 260–500 ft depending on target speed and grade.
• Speed tables / raised crosswalks: Flat-top (10–22 ft) to accommodate crossings and mid-block priority; pair with high-visibility markings.
• Speed cushions: Channel emergency axles while calming passenger cars; useful on primary response routes.
• Chicanes & pinch points: Alternating curb extensions or parking bays that create a gentle S-curve; add trees for visual narrowing.
• Mini-roundabouts: Yield-controlled intersections with traversable centers; reduce severe-angle crashes and enforce slow entries.
• Lane narrowing / road diets: Reallocate extra width to bike lanes, medians, or parking; narrower lanes reduce speed choice variance.

Cut-Through Volume Control

On residential streets that suffer from commuter bypass or navigation-app diversion, volume control mechanisms change permeability without eliminating local access.

• Full & diagonal diverters: Block through movements while allowing bikes and emergency access via bollards or mountable aprons.
• Modal filters (bike/ped permeability): Planters or islands that allow two-way walking/biking but prevent through motor traffic.
• Turn restrictions & time-of-day closures: Operational tools to mitigate peak-hour infiltration; pair with enforcement or signs plus cameras where legal.
• One-way conversions with contraflow bike lanes: Reduce shortcuts while maintaining neighborhood cycling connectivity.

Crossing, Pedestrian, and Bicyclist Safety

Calming isn’t only about motorists—it’s about creating predictable, short, and visible crossings and continuous bike routes. The elements below increase yielding, reduce exposure time, and improve comfort for all ages and abilities.

• Curb extensions (bulb-outs): Shorten crossing distance, improve sightlines, and physically prevent illegal parking near crosswalks.
• Daylighting: Remove parking within 20–30 ft of intersections to reveal people stepping off the curb; combine with signage and paint.
• Raised intersections / crosswalks: Bring the roadway up to sidewalk grade for continuous pedestrian priority and slower turning speeds.
• Median refuge islands: Two-stage crossings for multi-lane roads; add RRBELs (rectangular rapid-flash beacons) where warranted.
• Protected bike lanes & quick-build separators: Reallocate space; use armadillos, posts, or modular curbs to deliver immediate benefits.

Design & Siting: How to Choose the Right Measure

Selecting the right traffic calming configuration requires balancing target speeds, street function, access, transit, emergency response, utilities, and maintenance. Follow a transparent process so residents and decision-makers understand trade-offs.

• Define the problem precisely: Is it speed, volume, crossing risk, or all three? Map crashes, 85th-percentile speed, and cut-through patterns.
• Set targets: Example: reduce the 85th from 34 → 25 mph and cut injury crashes ≥ 30% within 12 months.
• Screen constraints: Grades > 8%, drainage inlets, bus routes, fire ladders, snow removal, truck routes, and school access windows.
• Pick a system of measures: Gateways at entries, humps or cushions mid-block, mini-roundabouts at nodes, curb extensions at crossings.
• Spacing & placement: Start ~300–400 ft and refine based on observed re-acceleration, driveway density, and noise concerns.
• Materials & phasing: Quick-build (paint + posts + modular curbs) → monitor → transition to concrete/bricks during resurfacing.

Data Collection, Modeling, and Before/After Evaluation

Credible traffic calming plans are grounded in data. Combine spot counts with probe-based speeds, simple microsimulation for queue impacts, and standard safety analytics. Make results public and repeat measurements after 30, 90, and 365 days.

• Speed & volume: Counters (tube or radar), turning counts, school arrival/departure observations, and weekend checks.
• Safety: Crash mapping, conflict analysis at crossings, and near-miss reporting from community apps.
• Operations: Travel time runs, bus schedule adherence, and emergency response coordination.
• Noise & quality of life: Resident surveys on comfort, noise, and perceived safety—often the most persuasive evidence.

Policy, Programs, and Funding

Sustainable traffic calming programs depend on clear policies and reliable funding. Codify eligibility, scoring, and delivery so projects move quickly and equitably.

• Eligibility & scoring: Minimum speed/volume thresholds; weights for proximity to schools, parks, transit, and equity priority areas.
• Process: Application → screening → pilot → evaluation → permanent build; publish timelines and responsible teams.
• Funding: Blend capital resurfacing, safety grants, Safe Routes to School, and quick-build budgets; leverage developer contributions.
• Maintenance: Assign owners for markings, reflectors, snow operations, and device repair; schedule refresh with paving cycles.
• Standards & consistency: Use standard profiles, signage, and markings so expectations are uniform across neighborhoods.

Traffic Calming Measures: Frequently Asked Questions

Do speed humps damage vehicles or slow emergency response?

Proper profiles (3–4 in high, 12–14 ft long) negotiated with emergency services provide meaningful speed reduction while maintaining response times. Where response is critical, use speed cushions that allow wide emergency axles to straddle the vertical element.

What’s the difference between a speed hump, table, and raised crosswalk?

A hump is a rounded vertical deflection to manage speed mid-block. A table has a flat top and works well for crossings and corridors with buses. A raised crosswalk is a speed table placed at a pedestrian crossing to increase visibility and priority.

How far apart should calming devices be?

Start with 300–400 ft spacing for 25 mph targets and adjust after observing re-acceleration, driveway noise concerns, and block lengths. Close spacing at the start and end of corridors creates “gateways” that set expectations.

Will drivers divert to parallel streets?

Some diversion is typical. Use a small-network approach: coordinate with adjacent streets using diverters or one-way conversions so cut-through traffic cannot simply shift one block over.

How do I balance bikes, buses, and deliveries?

Use cushions or longer tables for bus routes, maintain loading spaces near commercial frontages, and provide protected bike lanes or chicanes that physically separate riders from traffic.

Conclusion

Traffic Calming Measures transform streets from high-speed conduits into safe neighborhood connectors. By combining vertical and horizontal deflection, crossing upgrades, and network-level volume controls—selected through a transparent, data-driven process—agencies can reliably reduce operating speeds, prevent severe injuries, and improve quality of life.

Start with clear targets, coordinate with first responders and transit, phase quick-build pilots into permanent materials, and publish before/after dashboards. When the design itself enforces safe behavior, compliance follows naturally—and communities experience quieter, safer, and more inviting streets day and night.

Design for self-enforcement, measure what matters, and build trust with visible, repeatable results.