How Traffic Speeds Impact Cycling to Work: Insights from a Recent Study
Analyzing the crucial role of street speed limits and road design in encouraging or deterring bicycle commuting in cities.
How Traffic Speeds Impact Cycling to Work: New Study Findings
City planners and cycling advocates have long emphasized the importance of street design and speed limits for encouraging safer, more sustainable transportation. A recent study on traffic speeds reveals striking data about how the pace of vehicular traffic shapes peoples’ willingness to commute by bicycle. This article explores those findings, delves into their implications for urban development, and offers practical guidance for creating safer streets for cyclists.
Why Study Traffic Speeds and Cycling Rates?
Understanding the relationship between traffic speed and bicycle commuting is essential for guiding effective public policy and street design. Cities worldwide are attempting to shift more workers from cars to bikes—reducing air pollution, congestion, and creating more livable communities. However, evidence consistently shows that most people only feel comfortable cycling in low-speed environments where their safety is assured. This gap between aspiration and actual commuter behavior makes traffic speed analysis a key tool for urban transformation.
Study Structure: Measuring Traffic Speeds
Spot speed studies are a well-established method to quantify the actual speeds of vehicles on urban roads. Observers select representative locations, measure the time it takes for individual vehicles to pass between two reference points, and compile the results. In this study, average traffic speeds were mapped at locations throughout major cities. Notably, the methodology involved:
- Choosing diverse streets—main thoroughfares, side streets, and mixed-use corridors
- Recording vehicle speeds and times during peak commute hours
- Comparing percentiles (e.g., 50th and 85th percentile speeds) to posted limits
- Overlaying commuter patterns, notably cycling rates, against speed profiles
Calculating Speed Percentiles
Percentiles are key in spot speed studies. The 50th percentile marks the median speed, while the 85th percentile is used to estimate the maximum speed under typical conditions. This helps planners understand whether most drivers are obeying posted limits or if dangerous speeding is occurring. According to standard practice, studies recommend:
- Study lengths between 88 to 264 feet, depending on local average speeds
- Distinct vertical reference points to establish clear start and stop marks
- Statistical tables to extract median and higher percentile speeds from field results
| Average Traffic Speed | Recommended Study Length (feet) |
|---|---|
| Below 25 mph | 88 |
| 25–40 mph | 176 |
| Above 40 mph | 264 |
The Study’s Key Finding: Slow Streets Mean More Cyclists
Perhaps the headline takeaway is that bicycle commuting rates surge on streets where average vehicle speeds are under 20 mph. The number of cyclists observed was dramatically higher on slow-traffic roads as compared to main arteries where vehicles regularly exceeded posted limits by 10 mph or more. In practical terms:
What others are reading
- Streets with average speeds above 30 mph saw almost no commuter cyclists
- Residential and mixed-use streets, capped at 20 mph and enforced, had many more people choosing bikes
- Cycling rates decreased sharply with every incremental increase over 20 mph traffic speed
This confirmed prior urban planning assertions: traffic calming is essential to a thriving cycling culture.
Why Most People Avoid High-Speed Roads
People’s willingness to commute by bicycle is not just a personal preference—it is heavily shaped by their tolerance for traffic stress, which is largely dictated by speed and volume. The study finds:
- Even dedicated cyclists hesitate or refuse to ride on roads where vehicular speeds approach or exceed 30 mph
- Most potential cyclists fall into the lower stress tolerance groups, avoiding any road or intersection perceived as fast or dangerous
- A network’s overall connectivity is undermined when even a single stretch of high-speed road must be crossed or ridden along; the “weakest link” effect stops many trips entirely
This means that even if cities build beautiful bike lanes elsewhere, if cyclists must traverse just one high-speed road, many will avoid the route altogether.
Network Connectivity: Building a Cycle-Friendly City
The concept of network connectivity is critical in understanding how traffic speed affects cycling. For a cycling network to function, every link—the street segment, intersection, crossing—must feel safe for users, especially those with low stress tolerance. The study outlines four classes of cycling commuters based on this:
- Group 1: Least tolerant—only use off-street paths and quiet, low-speed roads
- Group 2: Somewhat tolerant—will use protected bike lanes, avoid high-speed roads
- Group 3: Moderately tolerant—can handle moderate traffic on some streets
- Group 4: Most tolerant—experienced cyclists willing to navigate mixed traffic even at higher speeds
For urban cycling rates to rise, planners must create a network where Group 1 and Group 2 cyclists feel comfortable. This involves eliminating—or at least mitigating—high-speed conflict points.
International Comparisons: Copenhagen’s Success Story
Drawing from Copenhagen, a city renowned for its cycling rates, the evidence is clear: traffic speed limitations, combined with protective infrastructure, turn cycling from a fringe activity into a mainstream commute option. Important policies include:
- Extensive 20-mph (30 km/h) zones throughout city neighborhoods
- Separation between bike lanes and moving traffic, either by curbs or road design
- Enforcement of speed limits alongside education campaigns about safety and environmental benefits
- Consistent government support for improving connectivity and eliminating dangerous corridors
In Copenhagen, traffic speeds and volumes are managed to keep stress levels low, leading directly to higher rates of bicycle commuting and improved quality of life.
Environmental Benefits of Cycling-Friendly Streets
Lower traffic speeds do more than encourage cycling. By shifting commuters from cars to bikes, cities can quickly achieve major gains in sustainability:
- Reduced carbon emissions and improved air quality
- Fewer traffic jams, shortening travel times for all modes
- Lower noise pollution, making neighborhoods more pleasant
- Better public health, as more people get routine exercise from active commuting
- Financial savings for individuals and cities, stemming from reduced infrastructure costs and health expenditures
By promoting cycling—and making it safer—lower speed limits are one of the most cost-effective ways for cities to hit climate and health targets.
Challenges and Barriers: Enforcement and Perceptions
Despite clear benefits, simply setting a lower speed limit does not guarantee compliance. The study notes several persistent challenges:
- Drivers often exceed posted limits, especially on wide, straight streets that encourage speed
- Lack of enforcement or physical calming measures can make speed limits meaningless
- Perceived danger remains even if average speeds drop; visual cues like bollards, trees, and narrow lanes help reinforce safety
Addressing these barriers requires investment in enforcement, street redesign, and education to shift both behavior and perceptions.
Policy Recommendations for Safer Cycling
Based on the data, several actionable recommendations arise for city officials and planners:
- Prioritize 20 mph speed limits (or lower) for streets designated as bicycle priority corridors
- Invest in physical traffic calming measures—speed humps, curb extensions, and raised crossings
- Develop protected bike lanes, fully separated from vehicular traffic where possible
- Enhance network connectivity so that no commute route requires crossing or traveling on high-speed segments
- Educate the public about the benefits and logic behind slower speeds and active commuting
- Enforce speed limits with both technology (cameras) and on-the-ground patrols
In short, if a city wants to be cycle-friendly, it must treat safe speeds as a foundational piece of its transportation strategy.
Frequently Asked Questions (FAQs)
Q: Why does average traffic speed matter more than posted speed limits?
A: Actual driving speeds often exceed the posted limits. Commuters assess real-world risk, not just rules. Lower average speeds, reliably enforced or engineered, lead to more confident cycling.
Q: Is 20 mph the “magic number” for cycling-friendly streets?
A: Yes, data from multiple studies indicate that a 20 mph cap makes the majority of residents feel safe enough to choose cycling, especially during commutes.
Q: Can protected bike lanes make high-speed roads safe for cyclists?
A: Protected lanes help, but only up to a point. If speeds are very high, even well-marked bike lanes may not induce confidence, especially for new or risk-averse cyclists.
Q: What physical street features encourage slower driving?
A: Features include speed humps, chicanes, curb extensions, narrower lane widths, trees close to the curb, and raised pedestrian crossings.
Q: Why do some cities struggle to implement lower speed zones?
A: Pushback often comes from drivers and businesses who fear congestion or inconvenience. Overcoming these concerns requires education, demonstrating safety and economic benefits, and strong leadership.
Conclusion: Slower Streets, Safer Cities, More Cyclists
The traffic speed study confirms a simple but powerful truth: Speed kills cycling enthusiasm. To make streets safe, cities must act to keep traffic speeds low—not just in name, but in fact. Only then will the vision of vibrant, healthy, bike-friendly cities become a reality for the majority, and not just an ambitious few.
References
- https://popcenter.asu.edu/sites/g/files/litvpz3631/files/learning/speeding/SpotSpeed.pdf
- https://nacto.org/wp-content/uploads/1005-low-stress-bicycling-network-connectivity.pdf
- https://www.nyc.gov/html/ia/gprb/downloads/pdf/Copenhagen_CityofCyclists.pdf
- https://www.safetyandhealthmagazine.com/articles/22411-bike-commuting-more-likely-when-speed-limits-are-low-study-finds
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