How Does Google Detect Traffic Congestion?

Following the introduction of Google Maps and Google Earth in 2005, Google soon became interested in providing real-time traffic information to its customers. However, with 3.9 million miles of public roads etched into the U.S. landscape, keeping tabs on all of the country’s traffic activity 24 hours a day proved to be a pretty tall order -- even for one of the most omnipresent companies in the digital age. Still, Google has managed to pull it off ... with a little outside help.

Sensor Assistance

1. In searching for a method to gather up-to-the-minute traffic conditions, Google discovered it wasn’t the only entity with an interest in the matter. Governmental transportation departments at local, state and federal levels -- hoping to gather planning statistics, improve accident response times and increase traffic flow -- had begun the widespread installation of solar-powered traffic sensors on major roadways throughout the country. Contracting with these transportation agencies to share the data generated by the sensors proved to be a mutually rewarding endeavor for both parties; Google was able to expand its traffic services while the transportation agencies were able to defray part of the sensors’ costs. Google executives then inked a multimillion dollar deal with Inrix, a traffic-related software company that independently gathers commuter data using sensors in 22 countries.

How Traffic Sensors Work

1. There are several different types of traffic sensors available, but three above-ground types have become more common in recent years: radar, active infrared and laser radar. The technology employed by radar traffic sensors has been around since World War II, when it helped the military track enemy vessels in the air and at sea. Mimicking that method, radar traffic sensors deploy a measureable area of microwave energy that is reflected back to the device when a vehicle passes through it. Active infrared and laser radar sensors operate in a similar manner, using low power infrared energy and infrared beams to form detection areas. In all three types of devices, the time it takes for the energy to bounce back to the sensor is compared to data collected in an unobstructed field to determine the size and speed of the vehicle passing through it. Using a wireless data network the information is immediately transmitted back to a server where it’s formatted and forwarded to subscribers via the Internet. Today’s technology allows each of these devices to monitor several lanes of traffic at a time.

Sweating the Small Stuff

1. While partnering with various transportation agencies provided Google with up-to-the-minute information about congestion on highways and major roads, it did little in the way of monitoring traffic on smaller rural and neighborhood streets. To accomplish this, Google turned toward the very people it was gathering the information for: its customers. GPS-enabled cell phones running the Google Maps application continually pass along each user’s location and speed to Google in real time. Using a technique known as “crowdsourcing,” Google combines the information provided by thousands of active cell phones to determine how swiftly traffic is moving through a given location. Although this feature can be disabled on cell phones, Google has attempted to discourage users from doing so by making sure all the information it gathers is anonymous.

Stacking the Pros Against the Cons

1. The technology utilized by Google to provide current traffic conditions isn’t without flaws. Radar sensors can’t help motorists avoid stalled vehicles because they can’t detect objects that aren’t in motion. Active infrared and laser radar sensors have been known to malfunction in dense fog or blowing snow. And the accuracy of crowdsourcing can be diminished when there aren’t enough cell phones providing data for a given area.