Traffic data

The data comes from FM radio station signals that are picked up by the traffic receiver that powers your Nuvi.

Sometimes the traffic is accurate, and sometimes its SOOOO not...

NAVTEQ Traffic-RDS collects, processes, and distributes real-time traffic conditions from a spectrum of traffic information sources across 98 Markets in North America.

Read more:
http://www.navteq.com/rdstraffic/

My Nuvi gets the traffic from Clear Channel. I'm lucky around here in Sacramento, we have a strong Clear Channel.

Some GPSr get their traffic from other sources, not sure what they are though.

I just wonder where the data comes from. Who supplies the reports?

The data is collected by the State and Local goverments. Most of it is automated. If you look closely at the road surfaces, you will see sensors embedded in the road that monitor traffic speed. There are usually 2 loops or 2 rectangular shapes that work like metal detectors. It's the same tecnology that is used to trigger traffic signals.

This data is fed into a nationwide monitoring system. Users such as Navteq, Google and others access it and publish it. Go to Google maps and zoom in on a major metro area, such as DC, LA or NY,NY and turn on the "Traffic". You will see grafic dispays of the traffic speeds. This data is the same data used to supply traffic info to a GPS. The sensors can detect when traffic has stopped and from this data, the computers monitoring this can determine how long a backup is and guesstimate the delay time.

Traffic is monitored by cameras as well (world-wide). Go to trafficland.com and check out what is available. And all the video is not there, by the way. Last time I looked, Pennsylvania wasn't there, but was available from the PA DOT. Guess they couldn't negotiate a fee or PA wanted all the thunder.

It's a very complex system and it is growing larger daily.

Less and less is being collected by inductive loop technology. Loops are expensive to maintain as any problem with the loop requires a road crew to replace the loop if it isn't the sensor module. That means shutting down the traffic lane to cut the road surface, lay the new wires, connect and test, then seal the cut with epoxy and wait for it to dry. Many are going to radar (those little camera like devices on the cross arms) which are more expensive to purchase, but don't have the maintenance costs.

The technology for inductive loops is way better than you think. They stay imbedded in the surface for many, many years with no problems. If one should fail, it only takes about an hour to replace it, as they remove the old one quickly and replace it quickly. No need to cut a new channel in the surface. The loops are pre-fabricated and come with long leads. These are usually replaced at night when traffic is low. Oh yeah, no "Bucket truck" required.

Placing a cross-bar on an interstate to hold a radar unit is extremely expensive, as it has to meet Federal saftey requirements. Also, it has to be extremely "Rock Solid", as it will generate false signals or be inaccurate when the wind is blowing. That means it must be placed between 2 pillars and that adds to the price.

Plus, using radar to just "monitor" traffic speed and density is not a good idea. I can see rear-end colisions, because some Bozo with a cheap Radar Detector slams on the brakes, if the detector is triggered, and then getting creamed by an 18 wheeler behind them. And since it is a "Transmitter" it has to be approved by the FCC and licensed if the power is high enough.

I have a friend that just retired from the city of Newport News Traffic Signal Dept. and he had told me that all the "Airborne" detectors were nothing but trouble and expensive to maintain. The units had to be shipped back to the manufacturer for repair or discarded. They were continually replacing them or re-aligning them. Loops rarely failed,

Less expensive - I don't think so.

Thanks for all the replies. Very informative. Now I know.