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Sensor Networks Could End Parking Rage

Cities hope systems that guide drivers to parking spots will reduce congestion and help downtown businesses.
January 25, 2012

In many urban areas, a third of the cars on the road have already reached their destination and are just circling the block waiting for a parking space. This leads to a cascade of problems, including pollution, traffic congestion, and accidents. Now massive arrays of networked sensors installed in city streets could significantly improve the situation by helping drivers find parking spots quickly.

Virtual valet: This app tells drivers where parking is available in San Francisco. Blue areas have open spots. Red ones don’t.

“We’re trying to make it really easy for people to find a parking space,” says Jay Primus, who manages San Francisco’s new SFPark program, the most advanced smart parking system in the United States. The city has recently installed magnetic sensors into the asphalt beneath 8,200 street parking spaces and is also collecting information on thousands more parking spots in garages, as well as from smart parking meters. All that information is linked to a central management system. Drivers can use a website or smart-phone app to access real-time data about where parking is available and how much it costs.

“Circling drivers are distracted drivers,” Primus says. “They’re much more likely to hit pedestrians, bicyclists, and other cars, and as they search for parking spots, making frequent turns and making frequent stops, they can cause unpredictable delays to the transit system.” He says the city hopes to reduce carbon dioxide emissions and collisions, improve transit reliability, and help businesses attract customers. The project is funded by a $19.8 million grant from the U.S. Department of Transportation.

In Los Angeles, researchers once found that cars circling for just three minutes to find parking in a 15-block neighborhood racked up over 350,000 miles of excess driving every year. Now L.A. is building a smart parking system similar to San Francisco’s. Within the next few months, the city will have sensors at about 7,000 street-side parking spots. “If you count the parking spaces, L.A. doesn’t have a shortage of parking spaces,” says Peer Ghent, a senior management analyst at the Los Angeles Department of Transportation. Instead, the problem is that drivers don’t know where the open spaces are. That’s an issue the smart parking system could fix with its network, which also allows cities to quickly see which cars have exceeded their time limit or are parked in front of fire hydrants and bus stops. In L.A., police officers can use a phone app to identify cars that are in violation, so they don’t have to check every car on the street.

Real-time data about parking-space occupancy allows city managers to set parking prices to encourage drivers to park in less congested areas. Since April, when the system went live in San Francisco, managers have changed the pricing structure three times. On one busy street in the Fisherman’s Wharf district, it costs $3 an hour to park; turn the corner and the price drops to $1.50.

Street sensor: The circular sensor shown here, developed by Streetline, detects the presence of a car and radios that information to a centralized database via a mesh network.

The smart parking apps will allow drivers to do more than find parking. Drivers who are late returning to their spots can use the app to add time to the meter remotely. Streetline, which is providing the technology for the sensor network in L.A., is allowing garage operators to use the app to publicize discounts, and drivers can use the app to reserve a spot in a garage. Eventually local businesses could also use the app to advertise discounts or to validate parking for customers, says Zia Yusuf, CEO of Streetline.

The sensor network in San Francisco was developed by Street Smart Technologies. Workers install each hockey-puck-shaped sensor by drilling a shallow hole in the street and gluing it in place so that it is flush with the surface. In snowy areas, this low-profile design will prevent the sensors from being scraped off the roads by plows. The devices include a magnetometer (which detects the presence of a car), a processor, a battery that lasts about five years, and radios for transmitting data to a central management system via a mesh network.

Although the system is simple on a conceptual level, it’s been challenging to implement. Electromagnetic interference from buried power lines can scramble sensor measurements, so Street Smart has had to install redundant sensors at some parking spots to ensure accuracy, says Kirby Andrews, a managing agent at the company. He says everyday activities in the city will make regular maintenance a necessity: construction workers might pave over sensors, for example, or dumpsters could be pushed into parking spots. “There are a hundred things that go on that are completely unanticipated,” he says.

It’s also a challenge to communicate the new pricing schemes to drivers. Those with smart phones can access the information with the SFPark app, but Primus says some drivers, especially tourists, may never know about the different rates. He is confident, however, that even if only a relatively small number of drivers use the app, that could still make a big difference in terms of parking availability: “We only need a few drivers to change where they park to open up spaces in congested areas.”

The systems are still too new to have produced good data about their impact on traffic congestion. But San Francisco is collecting such information and will report the results as part of the requirements for its federal grant.

“Most city parking is mismanaged or not managed at all, because you can’t manage what you can’t measure,” says Donald Shoup, a professor of urban planning at UCLA whose research has shown how much drivers looking for parking contribute to congestion. “Sensing networks, by revealing what’s happening in parking spots, will change the way cities work.”

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