HOV "Lanes"

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Re: HOV "Lanes"

Postby jwriddle » Mon Jul 29, 2013 1:54 pm

AndyPoms wrote:
jwriddle wrote:
AndyPoms wrote:The lane guidance in other GPS units is done essentially by segment - it doesn't actually know what lane you are in, but information about the number lanes on the segment you are on.

Besides at a 95% confidence level, civilian GPS is only accurate to 7.8 meters (just over 25 feet)(1) - and minimum lane width in the US is 12 feet (2) so 25 feet covers two full lanes on either side.


You're a walking Wiki of stats. :o
I looked it all up & I cited my sources (the little numbers in parentheses).


Now you're just showing off. ;)


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Re: HOV "Lanes"

Postby kentsmith9 » Fri Aug 02, 2013 5:08 am

When I first joined we added the ~10 mile segment of I-680 S (Sunol to Milpitas) with an HOV/HOT lane. I drive it every day and have a Plug-in Prius so I can use it as a solo driver. The lane is not physically separated, but there is a double white line (illegal to cross) and various entrances and exits along the 10 miles.

I have played with the GPS sensitivity. Generally speaking with the way we have it mapped the freeway is wide enough in most areas to give about 2 lanes of separation. If I start my route before I am in the lane, Waze keeps me in the main lane while I cruise down the HOT lane (up here that lane is typically at the limit at all times). If I shut down Waze and restart it while I am in the lane, it usually shows me in the HOT lane and gives me the proper HOT exit points to get off the freeway.

When being routed in the main lane and I am in the HOT lane, Waze updates my ETA live with earlier times in 1 minute increments (does not build up and suddenly change my ETA with a message). I assume this is altering the main lane timing for the non HOT/HOV drivers. Since Waze is able to assess I am in the HOV/HOT lane when I first start navigating, I would think it could ask me if I am in that alternate lane after being there for more than a few miles. I also assume that since Waze tracks actual vehicle paths even though it displays me in the main lane, it hopefully is not adding my faster time to the main lane average speed.

If anyone takes a look at this segment of I-680 S note that I recently found out the way we set it up as a freeway lane is not what was proposed so we still have to update that.
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Re: HOV "Lanes"

Postby russblau » Mon Jul 29, 2013 3:22 pm

I'm sure AndyPoms is right, but even without any stats, all you have to do is look at the GPS layer in the WME and you can see how wildly inaccurate some GPS readings are. If memory serves me right, I believe it takes 20-30 minutes of continuous operations for a GPS unit to reach full accuracy, too, so we are unlikely ever to approach "lane-level" accuracy for users with relatively short commutes.
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Re: HOV "Lanes"

Postby sketch » Fri Aug 02, 2013 5:39 pm

kentsmith9 wrote:When being routed in the main lane and I am in the HOT lane, Waze updates my ETA live with earlier times in 1 minute increments (does not build up and suddenly change my ETA with a message). I assume this is altering the main lane timing for the non HOT/HOV drivers. Since Waze is able to assess I am in the HOV/HOT lane when I first start navigating, I would think it could ask me if I am in that alternate lane after being there for more than a few miles. I also assume that since Waze tracks actual vehicle paths even though it displays me in the main lane, it hopefully is not adding my faster time to the main lane average speed.

This will probably affect the "current traffic" speed, yes, but it shouldn't affect historical data, provided that the GPS traces are accurate enough. That's done with later analysis once your drives are uploaded.
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