Big Data for Safer Streets

Is Cell Phone Data the Key to Making Cities Safer?

Image: SFMTA
Image: SFMTA

After the completion of the 14 Mission Rapid project, with its “red carpet” transit lanes, many motorists and business owners along the route claimed that traffic got more congested and dangerous. But a new analysis, released yesterday, shows a 36 percent reduction in speeding, a 30 percent reduction in fast accelerations, and a 21 percent reduction in hard braking on Mission. The study was done by Zendrive, a company that analyzes traffic using accelerometers and gyro-meters on drivers’ cell phones.

And late last week, the San Francisco Bay Area Planning and Urban Research Association (SPUR) held a panel discussion about using just such data to get the facts straight and to improve traffic engineering, enforcement and safety.

Previously, traffic engineers and policy makers had to do extensive surveys and look at crash data over years to figure out whether an intersection or street treatment was working. Now, however, they can easily collect data on issues such as hard accelerations and fast braking, enabling traffic engineers to quickly identify problem areas and tweak designs before people are hurt. This is one of the keys to achieving “Vision Zero,” San Francisco’s policy commitment to eliminate traffic-related fatalities by 2024, said Leah Shahum with the Vision Zero Network and one of the panelists.

For example, local residents had objected that the transit lanes on Mission would push traffic onto parallel streets such as Van Ness, causing more delays and crashes. But the data shows a different story: after turns on Market and Mission were eliminated and the transit-only lanes were created, nothing changed on Van Ness. “It will cause traffic on parallel streets” is a common charge against road diets and traffic calming. But David Ragland with the UC Berkeley Safe Transportation Research and Education Center, another of the panelists, said the data shows that’s just not the case. “It’s counter intuitive… but hugely powerful for policy makers, who can go back to constituents with this information.”

Jeff Tumlin, interim head of Oakland’s new Department of Transportation agreed, and said he saw similar results with the bike-protected lane on Telegraph. “Telegraph used to be four traffic lanes, but we narrowed it to one lane in each direction, and did protected bike lanes,” he explained, and the data showed “we were correct. As expected, there were more cyclists, but it also improved conditions for pedestrians, too, without delaying traffic…. We doubled the number of peds, and eliminated the number of crosswalk crashes, and increased retails sales.”

That said, Tumlin explained that getting that data required “expensive and tedious hand counts–but it was critical for telling the story so we can do more projects like that.” Moving forward, information from Zendrive and other sources of cell phone data will allow cities to analyze street conditions much more quickly.

In addition to monitoring streets and intersections and improving designs, phone data can also be used to track individual drivers who are unsafe.

“We use data and information so we can monitor [things like] phone usage and sudden deceleration. We want to make sure kids in our cars are being driven around in as safe a manner as possible,” said Joanna McFarland , head of HopSkipDrive, a Los Angeles-based ride-hail service for kids. “We don’t want situations where you were doing things that might be reckless to get someone there on time,” she said. Geometric information from cell phones helps them identify drivers who exhibit risky behaviors. This is also something that Uber has experimented with–using cell phone data to see if drivers are speeding and making erratic maneuvers.

It’s interesting to note that the same technology that McFarland’s company is using to screen drivers of children may have even greater potential. Privacy issues aside for the moment, there’s no technological reason why police forces can’t identify speeding or erratic maneuvers and go after reckless drivers in real time, based on this same cell phone information. Some day, it may even be possible to send a citation or suspend a license based on geometric data.

Meanwhile, Shahum said she’s become a “data nerd” and is focused on using data to push for safer designs, especially now that pedestrian deaths are on the rise. “People are saying enough is enough and we need to change our policies and road designs–so much of this starts with the data,” she said. The panelists agreed that while smart phones are distracting drivers and causing more collisions, they can also be the key to reversing this trend.

“This will all help cities understand their transportation networks better and allocate resources. It helps substantiate requests from across the country,” said Mollie Pelon, another panelist and a technology expert with the National Association of City Transportation Officials.

Zendrive, meanwhile, has an interactive map of hard braking, acceleration, speeding, and cell-phone use on and around Mission from before and after the transit lanes were added. In total, the map reflects data from over 100,000 trips, 7,500 drivers, and 1.1 million miles driven from January to October 2016 along the 14 Mission Rapid project corridor

What do you think about the privacy implications of monitoring people’s driving behavior in real time? Should this be used to tag individual drivers or just as a street-design tool? Post your take below.

As SPUR's talk last week, a panel discussed how to use data to make our streets safer. Photo: Streetsblog/Rudick
At SPUR’s talk last week, a panel discussed how to use data to make our streets safer. Photo: Streetsblog/Rudick

For more events like these, visit SPUR’s events page.

  • JustJake

    “Privacy issues aside for the moment, there’s no technological reason why police forces can’t identify speeding or erratic maneuvers and go after reckless drivers in real time, based on this same cell phone information. ”

    “Should this be used to tag individual drivers or just as a street-design tool? ”

    Neither. Cell phone data does not belong to anyone beside the user. Are you expecting people to ‘opt-in’ to real time tracking & surveillance? Might as well promote everyone getting a government mandated microchip, at birth. The lengths to which urbanists will go in order to improve streets & traffic…

  • thielges

    You may be interested to know that if you carry a cellphone, you movements are already tracked by the cell provider. And if you have any aps running, those ap providers may be receiving location tracking info. For example google maps will track your movements and send anonymous summaries back to the google servers.

  • bobfuss

    Only if your phone is switched on. When I don’t want anyone to know where I am, I switch it off.

    It follows that any study based on its data is somewhat selective and limited.

  • JustJake

    I’m aware of all this. I rarely have location services on, and generally avoid apps.

    User data sitting in an AT&T hard drive somewhere is fairly different than the notion of real-time law enforcement use. Under current law, a warrant is required for law enforcement to access user data.

  • Sfgeoninja

    Many newer model cars also have built-in navigation systems that transmit this information to companies like ZenDrive as part of the user agreement. So if you’re really not into anyone ever knowing your precise location, walking or biking are your best bets.

  • JustJake

    Being in the construction industry, typically I transport several hundred pounds of tools to locations that change every few days. Walk/bike is unrealistic for myself, as well as for many others. Staying away from ‘smart’ cars is easy enough however.

    PS: User agreements such as you describe are never a required part of a purchase, and hardware can be disabled.

  • Sfgeoninja

    Fair enough. No one is forcing you to turn the hardware on. If you wish to opt out that is your prerogative. Since most people don’t think twice about it, however, these companies will still be able to gather enough anonymized data to make decisions. The list of features you’ll need to disable to maintain complete privacy is getting longer by the minute. You’ll want to also disable bluetooth (location-based advertising) and any RFID-based chip technology found in Clipper Cards as well as in most new credit/debit cards.

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