I just noticed last week that Google now has traffic information for a handful of arterial streets. Here is what Columbus’ central area looks like as I write this at approximately 9:20 PM EDT on Thursday, September 10, 2009.
Here’s some more information from Google’s Blog:
Google Maps will now show you live traffic conditions on arterial roads in selected cities. Just zoom-in on the city you’re interested in, and click the “Traffic” button in the upper-right corner of the map. As you zoom in closer to an area of interest, we’ll color the arterial roads, in addition to the highways, to show current traffic conditions. Just as with the highways, the colors correspond to the speed of traffic (relative to the speed limit of the road): green is free sailing, yellow is medium congestion, red is heavy congestion, and red/black is stop-and-go traffic.
This is pretty cool, but I’m not 100% sure it’s all that accurate. Does Cleveland Avenue really have that much traffic congestion at 9:20 PM on a weeknight? I doubt it. I think the problem lies in Google’s calculation. They say they are showing traffic speeds relative to the speed limit of the road. However, over a corridor like High Street or Cleveland Avenue, you are bound to hit a few lights, so your average speed will always be less than the speed limit of the road. This will make the traffic show up yellow or red, even though it’s moving just as well as you would expect it to.
What I would suggest instead is that Google reference what traffic engineers call the free flow speed of the road instead of the speed limit. Free flow speed is what happens when there’s almost nobody else out on the road. It’s the best you can do when congestino isn’t a factor. I think it would be fairly easy for Google to aggregate the data for the best travel times on a corridor – probably late at night/early morning – over the course of a week or a month, and then reference that as the average speed.
If you’re interested in learning more about how Google is getting this information, and how you can help, check out this site:
If you use Google Maps for mobile with GPS enabled on your phone, that’s exactly what you can do. When you choose to enable Google Maps with My Location, your phone sends anonymous bits of data back to Google describing how fast you’re moving. When we combine your speed with the speed of other phones on the road, across thousands of phones moving around a city at any given time, we can get a pretty good picture of live traffic conditions. We continuously combine this data and send it back to you for free in the Google Maps traffic layers. It takes almost zero effort on your part — just turn on Google Maps for mobile before starting your car — and the more people that participate, the better the resulting traffic reports get for everybody.