For those who haven’t tried it, Google Maps has a button labeled “Traffic”. If you press it, many roads will be color-coded in any of 4 ways corresponding to the speed of the traffic currently on that part of the road. I have found it to be incredibly accurate and precise, and I’d love to know where they get their info. I don’t have a laptop to use in the car, but sometimes I’ll look at the map after arriving at home or work, and I’ll be amazed at how good it is.
If they would be showing traffic only for major roads, I’d figure that they are looking at traffic cameras similar to those I see on the local news. But it is very common to find a long stretch of a minor county road in one color, and a one- or two-block section in a different color. Are there that many traffic cams in my neighborhood?
Example 1: At this moment, the entire length of the NJ Turnpike northbound in Jersey City (labeled as Rt 78) - about 6 miles - is green, except for one yellow section about 200 feet long near Libert State Park.
Example 2: Westfield Avenue in Union County NJ (a.k.a. State Highway 28) is a main road only for the locals. The speed limit is 35 mph. The stretch from Elizabeth to Westfield (about 6-7 miles) is currently yellow in both directions, except for a red 1.1 mile section westbound, and a green 1.8 mile stretch eastbound.
I am amazed by this, and I guess my question is this: Where do they get such detailed and timely data, and are there any other websites which would show me similar stuff?
If the region has a transponder-based toll system such as FasTrak, EZ-Pass or similar, Google’s probably tapped into the traffic data that these systems put out.
Around here, there are dozens of small antenna alsong the freeways that do nothing but pick up the serial numbers of transponders and feed them to a central system that correlates it all and determine how long it took for a given transponder to go from Point A to Point B.
ETA: for NJ traffic, have a look at Redirect Page and for San Francisco area traffic, head over to www.511.org
Thanks, but for the entire northern 1/3 of NJ, it shows only 3.5 roads: 287, 78, 9A, and half of 24. Not even the Parkway! Not even laughingly close to the kind of detail Google gives.
I’ve read about some company (ies?) having access to the de-identified cell tower data. So in effect you’re seeing the speed at which a herd of cellphones are moving down the road.
I don’t have a cite, nor time to search for you now, but try chasing that idea.
With some further digging, I found that Caltrans partnered with someone called Traffic.com. Traffic installs and maintains the sensors for Caltrans and appears to be the leader in the traffic data business.
Interestingly, but perhaps not surprisingly, Traffic is a unit of Navteq - the dominant force in digital mapping and GPS navigation.
According to Traffic’s website, all of this comes to us thanks to some Federal legislation called Intelligent Transportation Infrastructure Program (ITIP).