Inside Inrix--How traffic data is collected, what it means to your commute

Traffic information for drivers on the go has come a long way since the days when it was limited to Bob in Chopper Nine, flying around the metropolitan area and reporting on whatever bridge or highway was beneath him.

Bob is still up there, at least in some media markets, but now he's only part of the picture. Today, traffic info comes from a variety of sources, sometimes even including the cars stuck in traffic themselves. The alerts you see on the GPS system in your car are likely coming from some combination of these sources, gathered up and redistributed by one of a very few companies that act as aggregators, compiling, cross-referencing, and verifying the information before shipping it back out. (Read our GPS buying advice and ratings.)

Kirkland, Washington-based Inrix is one such aggregator, and it lays claim to being the largest provider of traffic data in the world, even if it is a name unknown to most commuters. Inrix monitors real-time traffic flow on some 260,000 miles of roads in the United States, and it provides that information to a number of automakers, portable GPS device makers, and telecommunications companies, including AT&T, BMW, Ford, Garmin, Mercedes-Benz, TomTom, Navigon, and Sprint. Inrix employs about 60 people, most of whom are involved in the dark science of creating algorithms and analytics to make sense of all the data they gather.

Jim Bak manages public relations for Inrix, and part of his job is translating the science of collecting traffic information into ordinary English. He recently took some time with us to explain the main sources of traffic information in use today, and the role of each in getting the total picture. He then gave us a peek into what's coming soon.

Traffic Alerts: The oldest form of traffic-gathering information in use today, alerts are where Bob the chopper guy comes in. In addition to observations from aircraft, alerts can also include information from police, traffic cameras, emergency scanners, and reports from agencies that operate bridges, tunnels, and highways. Alerts are best for capturing events that might cause backups, like collisions and breakdowns. Media companies Clear Channel and Westwood One are two of the largest aggregators of this type of data, providing it to radio and television stations, and others, including Inrix.

Historical Data: State and federal Department of Transportation agencies maintain databases of historical traffic information for most major cities. Data typically comes from sensors embedded in roads. This helps identify how crowded I-90 in Chicago could be expected to be at, say, 3:00 p.m. on a Tuesday. While historical information is helpful, and some navigation systems from TomTom and others include it in their route planning, it can't factor in things like weather, crashes, road construction, or heavy traffic caused by sporting events. As Bak points out, no two Tuesdays are alike. But again, historical data is just one piece of the pie.

Real-Time Information: Roadway sensors and cameras can also provide current flow information for major roadways, but are usually limited to major cities. Sensors are effective for determining drive time information, however they're expensive and require frequent maintenance. Because of this, they're found only on major highways, and in certain major metropolitan areas.

Crowd sourcing: A newer and more granular source of real-time flow information comes from GPS navigation devices and mobile phones carried in vehicles, which can anonymously provide location and speed information. As portable GPS navigators have become more common and almost everybody now carries a cell phone, data from these devices has become increasingly available and reliable. More importantly, this info has made reporting on traffic conditions on secondary roads more feasible and cost effective.

But cell phones don't identify their location as accurately as GPS devices do, particularly if they're some distance away from the nearest tower. A GPS navigator pinpoints its location within a few feet. But according to Bak, a mobile phone might be off by 20 feet or more--enough to conceivably peg it on an adjacent roadway.

Inrix currently gathers data from some two million of these mobile telephone and GPS "drones" around the United States, the great majority of which are in fleet and commercial vehicles. Bak says the most reliable and consistent data comes from these vehicles, which regularly travel the same routes, rather than private individuals randomly passing through.

Bak sees crowd sourcing as the most valuable piece of the pie going forward, and the one most likely to provide up-to-date information with the least lag time. He says the next wave in crowd sourcing will take it to another level, but will rely on users being more proactive in reporting incidents and delays as they travel. He said devices and apps coming soon will offer users the option of sending an update instantaneously with the push of a button or their spoken voice if they see a collision or other slowdown. While he admits not everyone with the capability to report conditions would choose to do so, he anticipates a participation level of around 30 percent of drivers providing instantaneous reporting of road conditions—hopefully without being distracted.

The smorgasbord of sources Inrix uses to gather information currently includes some 400 different suppliers in addition to crowd sourcing. Most of their clients use some combination of the various sources available, and that is where the information comes from when you get an alert on your nav system. At least that's the way it works for now. Things are changing all the time.

Also read: "Understanding GPS navigation traffic services."