For much of the 20th century, transportation engineers believed that wider streets were safer streets. The conventional wisdom was that larger roadways provided greater visibility and more space for vehicles to avoid collisions. This roadway design principle quickly became engrained in transportation departments across the country and the academic institutions that trained their employees. But, this conventional wisdom proved to be a false assumption — one that came with deadly consequences.
When wider streets were put to the test using hard data, it became clear that the opposite of what was assumed was actually true. We now know that wider roadways generally encourage faster and more careless driving that increases danger for everyone. Meanwhile, narrower streets cause drivers to slow down and be more attentive to their surroundings. If you have ever driven down a narrow side street and an interstate highway, you know exactly what I mean.
The ideal width of streets is one of many examples when transportation planners got it wrong when they were guided by assumptions instead of data. That is why I am gravely concerned about Intro 1138, legislation currently before the City Council. The bill would dramatically change all 40,000 intersections across the city by instituting universal “daylighting,” which would prohibit parking a vehicle within 20 feet of a crosswalk.
It is a well-intentioned bill that aims to improve visibility so that drivers and pedestrians can more easily see one another. It is an idea that makes a lot of sense on the surface, but, a years-long, first-of-its-kind study conducted by NYC DOT found that it could result in up to 15,000 additional traffic injuries each year.
How is this possible? Candidly, it is not the conclusion we expected. We evaluated nearly 8,000 intersections across the city and found that intersections with the daylighting required by this bill had more traffic injuries than comparable intersections without it.
While these intersections gained additional visibility that should have made it easier for drivers and pedestrians to see one another, the data suggests that it also changed driver behavior in a way that reduced safety. Our study suggests that by removing the physical barrier caused by parked cars, a wider turn radius made it easier for drivers to more quickly and carelessly turn at intersections.
Our findings are eerily similar to the assumptions about wider streets. Just as transportation planners later came to realize that narrower roadways generally improve safety, not wider ones, our study finds that a tighter turn radius is preferable to a wider one. We even reached out to cities across the country to see if they conducted similar studies so that we could take those findings into account, but we found none.
Like the assumptions about the safety benefits of wider streets, assumptions have been made about universal daylighting that are not backed by rigorous analysis.
Our study did find that “hardened” daylighting — where you replace a parked car with a smaller physical object near the intersection — can have safety benefits. That is because you get the benefit of improved visibility while retaining the tighter turn radius.
We have long used hardened daylighting as one of many tools to make streets safer. We apply it situationally by placing objects like concrete blocks, bike racks, or flower planters near certain intersections. We will continue to use this treatment where it can be most effective. And, we will use other street design techniques where they make the most sense. There is not a one-size-fits-all answer to street safety, and we must do what works and do it in the places where it is most needed.
I have been proud to be an advocate for street safety throughout my career. Whether as DOT commissioner or serving on the City Council, including as its Transportation Committee chair, I have fought hard for safety — even when it has been difficult.
Throughout this time, it has been an honor to stand shoulder-to-shoulder with other transportation safety advocates and families who have lost loved ones to traffic violence. I know many of them care deeply about this bill, but the dedicated career professionals at NYC DOT who carefully and meticulously studied this issue found that universal daylighting would make our streets less safe. That is why I strongly oppose this bill and encourage my former colleagues on the City Council to do the same.
Let’s work together on bold street redesign projects, expanding hardened daylighting where appropriate, and prioritizing the most effective policies that make our streets safer for all.
Rodriguez is New York City’s transportation commissioner.
