A headline circulating recently claims that a new study found segregated cycling networks reduce all traffic deaths by 11 percent, including for drivers. The core idea behind that headline is well supported by research — but the specific 11 percent figure is not. We could not locate a published study with that exact number, and the best-documented research actually points to a far larger effect. A landmark 13-year study by researchers at the University of Colorado Denver and the University of New Mexico, published in the Journal of Transport & Health in May 2019, found that US cities with protected, separated bike lanes had 44 percent fewer road deaths and 50 percent fewer serious injuries for all road users — drivers included — compared with the average city.
In other words, if anything, the viral 11 percent figure undersells the evidence. The study examined data from 1990 to 2014 across 12 large American cities, and the results were consistent: where physically separated cycling infrastructure was built out, everyone on the road became safer. Portland, Oregon, saw fatality rates fall roughly 75 percent over the study period as it expanded its bike network. Seattle saw a 60 percent decline, San Francisco about 49 percent, Denver 40 percent, and Chicago 38 percent. This article walks through what the research actually shows, why protected bike lanes protect people who never touch a bicycle, and what the limitations and caveats are — including why you should be skeptical of any safety statistic you can’t trace to a primary source.
Table of Contents
- Do Segregated Cycling Networks Really Reduce Traffic Deaths for Drivers Too?
- Why Protected Bike Lanes Calm Traffic — and Why “Safety in Numbers” Isn’t the Mechanism
- What the International Evidence Says
- Protected Lanes vs. Painted Lanes vs. Sharrows — What Actually Works
- The Problem with Viral Statistics — Where Did “11 Percent” Come From?
- Who Benefits Most From Segregated Networks
- The Future of Street Design
- Conclusion
- Frequently Asked Questions
Do Segregated Cycling Networks Really Reduce Traffic Deaths for Drivers Too?
Yes — and this is the most counterintuitive and important finding in the literature. The 2019 Journal of Transport & Health study did not just measure cyclist deaths. It measured road deaths across the board: drivers, passengers, pedestrians, and cyclists. Cities with robust networks of protected bike lanes had dramatically better outcomes for all of those groups. The 44 percent reduction in fatalities applied to everyone using the street, not just people on bikes.
Compare this with the conventional assumption that bike lanes are a zero-sum trade: space taken from cars, given to cyclists, with safety benefits flowing only to the latter. The data contradicts that framing. New York City’s experience on 9th Avenue is a concrete example — after the city installed a protected bike lane there, injuries to all street users fell 58 percent, according to PeopleForBikes. Drivers crashed less, pedestrians were struck less, and cyclists were hit less, all on the same redesigned corridor. The distinction between protected lanes and painted lanes matters here. The research consistently shows that paint alone does little; physical separation — curbs, planters, parked cars, bollards — is what produces the measured effect.
Why Protected Bike Lanes Calm Traffic — and Why “Safety in Numbers” Isn’t the Mechanism
For years, the dominant theory was “safety in numbers”: more cyclists on the road make drivers more alert and careful, reducing crashes. The Colorado–New Mexico research team tested that hypothesis and found it didn’t explain the results. The safety gains were not driven by the sheer number of cyclists. Instead, the infrastructure itself was acting as a traffic-calming mechanism. Building a protected bike lane typically narrows the roadway available to cars, shortens pedestrian crossings, and signals visually that the street is a shared space rather than a throughway. Drivers respond by slowing down, and lower speeds mean fewer and less lethal crashes for everyone.
This finding has practical consequences. It means a city doesn’t need to wait for cycling mode share to climb before the safety benefits arrive — the benefits come from the concrete and curbs, not the headcount. It also means that simply encouraging more people to ride, without changing street design, is unlikely to deliver the same results. A limitation worth flagging: the study is correlational across cities over time, not a randomized experiment. Cities that build protected bike networks often pursue other safety measures simultaneously — lower speed limits, signal retiming, Vision Zero enforcement — and untangling those effects perfectly is impossible. The researchers controlled for many variables, but readers should treat the precise percentages as strong evidence of direction and magnitude, not as a guaranteed outcome for any individual street.
What the International Evidence Says
The American findings line up with decades of European data. Danish research has found that segregated cycle space reduces cyclist deaths by 35 percent, which is part of why Copenhagen’s network of physically separated cycle tracks has become the global reference design. Denmark and the Netherlands built their networks over decades, and both countries combine low cyclist fatality rates with high cycling participation — including children and the elderly, populations that largely disappear from cycling statistics in countries without protected infrastructure.
The global stakes are significant. The World Health Organization reported in May 2025 that more than a quarter of all road traffic deaths worldwide are pedestrians and cyclists, and it explicitly called for safer walking and cycling infrastructure as a road-safety intervention. Meanwhile, the European Commission reported in March 2026 that EU road deaths fell 3 percent in 2025 — continued but slow progress, and a reminder that incremental policy produces incremental results. The cities that have achieved step-change reductions, like Portland’s 75 percent decline, did so through sustained physical redesign of streets.
Protected Lanes vs. Painted Lanes vs. Sharrows — What Actually Works
Not all bike infrastructure is equal, and the differences show up directly in injury data. At the bottom of the hierarchy are sharrows — painted bike symbols in mixed traffic — which multiple studies have found provide little or no safety benefit. Painted bike lanes are a modest step up but offer no physical protection and are routinely blocked by parked vehicles. Protected lanes, separated by curbs, planters, or rows of parked cars, are where the large, measurable reductions appear, both for cyclists and, as the 2019 study showed, for drivers and pedestrians. The tradeoff is cost and political friction.
A sharrow costs a few hundred dollars per block; a curb-protected lane can cost orders of magnitude more and usually requires removing parking or a travel lane, which generates opposition. But the comparison cuts the other way when you count outcomes: cheap infrastructure that doesn’t reduce deaths is not actually cheap. Cities like Seattle and San Francisco, which invested in genuine separation, saw fatality declines of 60 and roughly 49 percent respectively over the study period — returns that no paint-only program has matched. For advocates and local officials, the practical takeaway is to push for network completeness as well as quality. A protected lane that ends abruptly at a dangerous intersection transfers risk rather than eliminating it. The cities with the best results built connected networks, not isolated showcase corridors.
The Problem with Viral Statistics — Where Did “11 Percent” Come From?
Here is the warning this article exists to deliver: the “11 percent” figure in the circulating headline could not be traced to any published study. It may be a distortion, a misremembered fragment of a larger finding, or a number generated somewhere in the chain of aggregation that produces social media road-safety content. Whatever its origin, no primary source matching the claim appears in current research databases or news coverage. Responsible publications — and responsible readers — should not repeat a statistic that cannot be sourced. This matters beyond pedantry.
Road-safety policy fights are won and lost on credibility. When advocates cite numbers that opponents can debunk, the entire evidence base gets tarred, including the rigorous findings. The irony in this case is acute: the verifiable research (44 percent fewer deaths, 50 percent fewer serious injuries) is far stronger than the unverifiable claim. Anyone arguing for protected bike lanes is better served citing the Journal of Transport & Health study directly, with its 13 years of data and 12-city sample, than passing along an orphaned percentage. The broader lesson: before sharing any traffic-safety statistic, find the study, check the publication, and confirm the number appears in it. If you can’t, don’t.
Who Benefits Most From Segregated Networks
While the safety gains accrue to everyone, the distribution is not uniform. Cyclists and pedestrians — the road users WHO data identifies as more than a quarter of global traffic deaths — see the most direct protection, because they are the ones physical separation shields from multi-ton vehicles.
Children, older adults, and inexperienced riders benefit disproportionately, since these groups are the most deterred by mixed-traffic riding. New York’s 9th Avenue redesign illustrates the breadth of the effect: the 58 percent injury reduction covered every category of street user, which is why protected lanes are increasingly framed as pedestrian and driver safety projects, not just cycling projects.
The Future of Street Design
The direction of travel in transportation engineering is clear. The 2019 findings have filtered into design guidance, and a growing number of US cities now default to protected designs for new bike facilities rather than paint.
The WHO’s 2025 call for safer walking and cycling infrastructure adds international institutional weight, and the EU’s slow 3 percent annual decline in road deaths is pushing European regulators toward more aggressive street-level interventions. Expect the debate over the next decade to shift from whether protected networks work — the evidence question is largely settled — to how fast cities can build them and how to fund connected networks rather than fragments.
Conclusion
The viral claim that segregated cycling networks cut all traffic deaths by 11 percent could not be verified, but the truth behind it is better documented and more dramatic. The strongest available research — a 13-year, 12-city study published in the Journal of Transport & Health — found that cities with protected bike lane networks had 44 percent fewer road deaths and 50 percent fewer serious injuries for all road users, drivers included. The mechanism is traffic calming: physically separated lanes reshape streets in ways that slow cars and prevent crashes across the board. City-level results, from Portland’s 75 percent fatality decline to New York’s 58 percent injury drop on a single redesigned avenue, reinforce the pattern.
For readers, the next steps are twofold. First, when you encounter road-safety statistics, trace them to a primary source before repeating them — the credible numbers are strong enough that nobody needs invented ones. Second, if you want safer streets in your own city, the evidence says to advocate for physically protected, connected bike networks rather than paint. The data shows they protect everyone, whether or not they ever ride a bike.
Frequently Asked Questions
Did a study really find an 11 percent reduction in all traffic deaths from segregated bike lanes?
No such study could be located. The figure appears to be unsourced. The closest verified research, published in the Journal of Transport & Health in 2019, found a 44 percent reduction in road deaths in cities with protected bike lanes.
Do protected bike lanes make driving safer too?
Yes. The 2019 study measured fatalities for all road users, including drivers and passengers, and found the safety benefit extended to everyone. New York’s 9th Avenue protected lane cut injuries to all street users by 58 percent.
Why do bike lanes reduce crashes for drivers?
Researchers found the infrastructure acts as a traffic-calming mechanism. Protected lanes narrow car space and visually signal a shared street, prompting drivers to slow down — and lower speeds mean fewer and less severe crashes.
Are painted bike lanes as effective as protected ones?
No. The large safety gains in the research come from physical separation — curbs, planters, or parking-protected designs. Paint alone provides little measurable protection.
Which cities have seen the biggest improvements?
Over the study period, Portland, Oregon, saw road fatalities fall about 75 percent, Seattle 60 percent, San Francisco roughly 49 percent, Denver 40 percent, and Chicago 38 percent as they built out bike infrastructure.
How big is the global problem for cyclists and pedestrians?
According to the World Health Organization (May 2025), more than a quarter of all road traffic deaths worldwide are pedestrians and cyclists, prompting WHO calls for safer walking and cycling infrastructure.
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