[mgerbasio]

Living in overcrowded Northern NJ, traffic is a big factor deciding how I'll get into Manhattan or just about anywhere around here.

Google Maps now uses the data it collects via cell phones with GPS running gm to build up to date traffic data. For example, you can now see cross streets in Manhattan. RIM recently purchased DASH for similar technology.

Now I can see all the roads that go where I need to be are clogged and I'm less frustrated sitting in my car wondering if I should have taken a different route

[ifonline]

Unfortunately, it isn't reliable at all. For example, both Google Maps on my phone and Google Maps online show that traffic is at a standstill just outside my office window. However, there is absolutely no traffic backed up as far as the eye can see.

I wouldn't plan my trips based on this, that's for sure.

[Dubdub]

Depends upon how often it is updated.

And the old adage applies - GIGO "Garbage In, Garbage Out".

[mgerbasio]

I just posted a question on Google Groups Maps Support asking how often the information is updated and how many samples are needed before traffic shows up.

I'll update my experience in the NYC Metro area after a few days of use. Like to here what others have to say.

[teddeli]

I have found the Garmin Automobile GPS traffic as well as AM traffic radio reports to be unreliable as well.

[mgerbasio]

I had Garmin XM traffic on a SP2730, it only covers the major roads. i'm not going to see cross streets in NYC or some of the smaller highways. Also, that service has a monthly fee and I need a GPS to use it.

I used Google Maps on a trip to Philadelphia yesterday and found that the traffic locations were accurate, better than anything else I've seen. I did have some problems.

At least once the GPS location was completely wrong and I had to do a reset to get it working properly. A few times the traffic wouldn't load but the maps and gps seemed to be working; I'd get a data connection error in GM. Reset didn't clear it but it just started working again in 15 minutes or so.

As for traffic, I'd disagree with what should be red vs yellow and it would be nice to have the traffic alert triangles with the speed shown and a clear indication when traffic is backed up in car/truck or local/express lanes. But the location and distance of a slowdown was pretty good.

[Dubdub]

XM Traffic is also somewhat delayed in my experience. The best that I have found are the local radio stations that report traffic every so often, like Boston's WBZ 1030 AM with traffic on the 3's. Another very good source, at least here in new England (and maybe other places) is dialing 511 on your cell and picking the route(s) you want.

[takeshi]

If you have something like this in your area (reads transponders in cars to measure traffic flow) it's likely to be more reliable as well:
Houston TranStar Real-Time Traffic Map

[clevebb]

How would google know whether I am at a stand still in traffic or sitting on a bench on the side of the road?

[jmwking]

Originally Posted by clevebb

How would google know whether I am at a stand still in traffic or sitting on a bench on the side of the road?

The other folks going by in their cars, of course. They just need some critical volume of folks before reporting.

-jk

[clevebb]

i think the hundreds of people in an office building may be enough critical volume for it to thing there is a stand still at 11am when no one is driving. Of course it depends on which city though

[jmwking]

Originally Posted by takeshi

If you have something like this in your area (reads transponders in cars to measure traffic flow) it's likely to be more reliable as well:
Houston TranStar Real-Time Traffic Map

[rant]Great idea, but it's another red/green map! Doesn't work so well for the several million of us in the US who are color-blind!

Google maps makes the red/green difference dramatic, but I can't tell their yellow from their green. [/rant]

-jk

[jmwking]

Originally Posted by clevebb

i think the hundreds of people in an office building may be enough critical volume for it to thing there is a stand still at 11am when no one is driving. Of course it depends on which city though

If a few users are going by at 35 mph, they can probably figure out that traffic is flowing. The Google knows all!

-jk

[ifonline]

But by that logic, if three of four lanes are blocked and at a standstill, and only one lane is traveling, how would Google be able to distinguish this situation from an office building full of people next to a two lane road?

[mgerbasio]

I'm not nearly as smart as the google internet god but I would think they track each google user over a period of time to determine if they are really "on the road". Also, if you're in a building you probably don't have a GPS signal unless you have a really good GPS receiver and are very close to a window; that takes a large portion of the people off scan.
Traffic, like blocked lanes, has a "signature" they'd expect to see. I know there is an entire field of engineering devoted to traffic so there are patterns and statistics that they're looking for to determine flow and probably a minimum number of reported users which is why all roads don't have traffic reported.
I think it must get more difficult say on 57th Street in Manhattan where the street traffic runs East and West and is very slow during the day. Determining foot traffic vs street traffic when both are moving at pretty much the same speed seems challenging. There I would think they look for start/stop as opposed to walking speed to see who is actually in traffic. I wonder if they actually track you over a long period of time to see if you're walking vs driving. Then if you get into a cab or bus, how does that look on the map as buses have frequent stops. It would certainly be in interesting white paper.

[ifonline]

Good points, and I'd be interested in seeing just how they calculate walking versus slow traffic versus people in an office building, etc. Could be fascinating.

[mgerbasio]

In NYC today and the traffic was wrong, at least on midtown streets virtually every time. It showed as "red" when the traffic was pretty light on 57th Street, 7th Ave, 8th Ave. So I guess it needs more work.