SF’s Freeway-Like Streets Increase the Risk From Distracted Drivers

Image: Zendrive
Image: Zendrive

Distracted driving in SF is no accident. A new map of cell phone use by drivers in SF reveals where drivers are most likely to use a mobile device, increasing the risk of crashes and injuries, and the pattern is unmistakable.

There’s one thing that streets with high rates of distracted driving have in common: They’re designed like freeways.

According to the map created by Zendrive, which “measures driving safety using only the sensors on a driver’s phone,” the streets with the most mobile device use by drivers were overwhelmingly designed as routes to freeways, leading to on-ramps and off-ramps, especially along the Central Freeway that divides the South of Market and Mission districts.

Sections of Duboce, Folsom, Eighth, 10th, and the interchange at Brannan and Division Streets all ranked in the top 10 of distracted driving streets.

Also high up the list were Fell and Oak Streets and 19th Avenue, which act as surface highways. Fell and Oak whisk west side drivers to and from the Central Freeway, and have synchronized traffic signals so drivers don’t have to worry about stopping often.

It stands to reason that wide, multi-lane streets designed to lull drivers into “cruise-control” mode fail to keep their attention. As Tom Vanderbilt wrote in his book Traffic: Why We Drive the Way We Do, “The relative ease of most driving lures us into thinking we can get away with doing other things.

In a dense urban setting like SF, distracted driving is often deadly for people walking and biking, as Zendrive wrote in a blog post:

Within the course of our work, we’ve tracked 1100 drivers over 37,500 miles across San Francisco, and measured cell phone use while driving, among many other safety metrics such as speeding or rapid acceleration. Any of these behaviors can be the cause of a collision with a bike, but distracted driving due to phone use while driving constitutes a special hazard to cyclists.

Zendrive created a map that overlays its phone use data with bike traffic and 10 recent years of collision data. SF’s busiest bicycling streets, like Market and the Wiggle, don’t see high levels of distracted driving for the most part. That’s no surprise, either — Market has plenty of street life to grab the attention of the few drivers who use it.

But Zendrive’s map did show some spots where drivers frequently use phones and cross major bike routes, such as Valencia and Duboce Streets. A driver barreling down Duboce destroyed a bike corral in 2012.

In 2012, a driver on Duboce Street plowed into a bike corral on the corner of Valencia Street, a hot spot for phone use among drivers. Photo: Erika Kali, Uptown Almanac

At many Fell Street intersections along the Panhandle, people on bikes are at heightened risk from distracted drivers. At Fell and Masonic Avenue, the SFMTA had to install a second left-turn signal arm before drivers stopped crashing quite so frequently into people walking and biking in the Panhandle crossing. Drivers who were caught by the red-light camera complained that they didn’t see the original traffic signal.

“This study underscores the need for a comprehensive, safety-first approach on our city streets,” said Tyler Frisbee, policy director of the SF Bicycle Coalition. “San Francisco can reduce traffic deaths and serious injuries to zero, which is what the city has committed to with a concrete approach known as Vision Zero. Encouraging everyone to pay attention is a crucial part of improving our streets, and hopefully this study will re-emphasize the need to prioritize safety when designing our roadways.”

Zendrive didn’t overlay its distracted driving map with pedestrian injuries, but it has much in common with the city’s WalkFirst map, which marked the streets with the highest rates of pedestrian crashes. Both maps highlight many of the same speeding-plagued streets in SoMa and near freeway ramps.

  • 94110

    Nowhere does it mention Zendrive’s methodology for distinguishing drivers from passengers.

  • twinpeaks_sf

    The study “FAQ” is here: https://www.zendrive.com/references/sf-bike-safety-2015/

    Not entirely clear the exact methodology they used. How do you know a driver is using the phone and not a passenger? Also, some (not all – see Van Ness) of these results closely follow traffic volumes. More driving means more phone use.

  • keenplanner

    Passengers? How many people actually carry passengers?

  • I’m waiting on an inquiry with Zendrive for any info on distinction between passengers. As for traffic volumes, there do seem to be known corridors with heavy car traffic that aren’t highlighted with a commensurate level of phone use. The data does seem to have some meaningful distinction from traffic patterns.

  • twinpeaks_sf

    No question – the results are very intriguing!

  • SFnative74

    To say that these types of roads encourage cell-phone use sounds like a theory. Maybe cell-phone use is higher on those streets because there are many more drivers on a four lane arterial than a two lane neighborhood street.

  • HuckieCA

    I rather question some of the methodology used in creating this, because it sounds like big data fishiness to me, at least on first glance. (By which I mean, when you have a hammer, every problem looks like a nail, i.e., I have only have data on these two factors, so clearly they must be correlated.) Rather, I look at their maps and think, if there are high-risk areas on Division/Duboce St. for bicyclists, are those risks really due to distracted driving? Or is it more likely that they are due to a combination of high traffic, high merging/lane changing, and narrow roads with no biking infrastructure?

    Furthermore, if you check out the Zendrive blog post on how they created this map (http://blog.zendrive.com/post/115025966432/the-top-10-riskiest-biking-hotspots-in-san), you’ll notice that the map for cell phone use and the map for biking risk due to cell phone use, are more or less a 1:1 correlation. However, when comparing the biking risk due distraction and the frequency of bike accidents maps, they are not highly correlated. The red dots for biking risk due to cell phone distraction do not overlap with the red dots for top 10 accident spots. This tells me that distraction might not be the key cause of biking crashes, and in fact, distraction is only coded as a factor in about 16 percent of crashes (according to NHTSA), so that leave the field of crash causes quite open.

  • datbeezy

    Seconded. They give no background on what constituted “distracted” – when I drive I frequently have my phone on GPS mode in a little holster – am I a “distracted driver” compared to someone who was a GPS router or has it built into their vehicle?

  • HuckieCA

    The article doesn’t say if it’s texting vs. just hands-free phone use, which makes a very large difference since texting has about a 2300% increase in risk while hands-free phone use has maybe a 30% increase in risk. Also, if you note where the locations for high phone use are, they are near freeway entrances or exits, and this makes some sense. Generally, when I’m entering the city, I’m making a call or sending a voice2text message to let people know where I am or coordinate what I’m doing. Same goes for when I’m leaving somewhere. However, what we really need to know is who the people are that they are monitoring? Clearly they must be fleet drivers of some sort, and perhaps their job has some reason for them to be communicating as they enter or leave the city? We don’t know, and probably won’t know, because this is a blog post and not a peer-reviewed scientific paper.

  • Jimbo

    its because people are using these streets to get to work on the freeway, and using their phones to do work while they are stuck in traffic. taking away the freeway like structure of these roads won’t fix the problem. the problem is traffic and the time it takes to get to the freeways. we need fast streets for cars to get to the freeway faster. if the cars can move faster, then less cell phone use.

  • Sure. Where do you live? We’ll put the traffic sewer right there.

  • I think you mean hypothesis.

  • 66 City

    The problem is that we’ve spent 50+ years engineering roads on the premise that it’s OK for people to spend hours a day driving great distances to live their lives. We’re now realizing that this doesn’t scale and isn’t affordable by society. Letting lots of people drive into a city plainly diminishes the life lived in the city.

  • Duane

    You park you bike in the street and it gets hit by a car….boo hoo….what do you expect…..who was the A-hole who suggested putting bike parking on the streets. STUPID IDEA. There are so many places to lock bikes….in the old days bike parking was NEVER an issue. We just locked our bike to a parking meter or street sign….nobody complained. I have a novel idea…..solve the problems that exist rather than make problems to solve.

  • Sorry about the delay here, my fault, but here are the responses from ZenDrive:

    “1) The data is from driver specific apps, so we have a high confidence that the results are based on driver phone use, rather than passenger phone use.

    2) Yes, the amount of distracted driving was normalized to the overall amount of driving recorded at each intersection, and our results only included intersections with a large enough sample of driving to have confidence in the rate of distraction, and to focus on intersections with higher overall risk – meaning high volumes of both cars and cyclists.”

  • twinpeaks_sf

    Interesting – thanks for following up.

    Sounds like a lot of Uber and Lyft drivers were included in the sample…

  • In the old days there were many fewer people biking.

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