Shortest Time Routing?

 

On a recent trip from GA to Dunedin Fl the Garmin Nuvi 3590 routed me of I75 short of Tampa. On the ride home it took me through Tampa. Even accounting for traffic delays it seems to me that the routing was incorrect.

Any thoughts?

There

There is no setting for Shortest Time. There is a setting for Faster Time and one for Shorter Distance.

In either setting it's possible that you'd get 2 different routes coming and going to a specific location. The Nuvi takes into account many things when calculating a route so depending on things like what advoidances you have set, how may left turns are involved in your route (take longer than right turns), etc. the GPS will often find a different route between points A and B than it will between B and A. Sometimes that different route doesn't seem like the right one to us. laugh out loud

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Nuvi 350, 760, 1695LM, 3790LMT, 2460LMT, 3597LMTHD, DriveLuxe 50LMTHD, DriveSmart 61, Garmin Drive 52, Garmin Backup Camera 40 and TomTom XXL540s.

What's often been said

The GPS is a poor replacement for common sense. If the route looks to be inefficient, it truly may be.... I usually zoom out, and see if there is another better (looking) way. More tan half the time, I'm right (but not always...)

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Striving to make the NYC Metro area project the best.

I always support the theory

I always support the theory (without any evidence) that the GPS map data begins with the local government jurisdiction and their interests have nothing do to with your Nuvi routing. So when their data (which supports their needs) produces a poor route choice, you should not be surprised.

The point is that if you care about the route, you always need to look ahead enough to know it is reasonable and force corrections if it is not.

If you wish to be really cynical, you can envision the stereotypical government employee and then be pleased about how well the Nuvi routes.

What makes it faster?

t923347 wrote:

There is no setting for Shortest Time. There is a setting for Faster Time and one for Shorter Distance.
...

In the Faster Time setting, does it (1) consider the road type (freeways versus surgace roads) or (2) does it try to use roads with the highest speed limits or (3) does it also consider the traffic information?

I wish

...there was an avoidance for traffic lights or surface streets.... Too many times, the nuvi takes me off the interstate to route me through a highly populated area when a trip further down the interstate would have taken me less time. I'll gladly drive an extra 25 miles to avoid a dozen lights....

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Striving to make the NYC Metro area project the best.

Very Interesting...

Something I never thought of.

Nuvi1300WTGPS

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I'm not really lost.... just temporarily misplaced!

question to garmin

jale wrote:

In the Faster Time setting, does it (1) consider the road type (freeways versus surgace roads) or (2) does it try to use roads with the highest speed limits or (3) does it also consider the traffic information?

I don't think anybody here will be able to tell how Garmin algorithm works. You may try to ask Garmin directly, but probably still will not get an answer. This kind of data is treated as secret, as you can easily buy mapping data but problem is with effective and efficient routing algorithm.

Zoom Baby Zoom

I agree zoom out and see the big picture. I have been routed off the highway then back on 1/4 mile later. I just stayed on and made the drivers choice decision.

John,

GAJohn wrote:

Shortest Time Routing?

My nuvi 1450 has three modes:

Faster time
Less fuel
Shorter distance

I think you've got to be cautious using the Shorter distance mode - - it can be a serious time waster.

I'll never forget a story a friend told me when he got his first GPS years ago. He and a friend were traveling from Miami to Boston and it seemed logical to him to set the device to "shorter distance" and they were off! It took them 1.5 days of travel to reach the Georgia border using that mode sad

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(2) Nuvi 1450LMT + 3597LMTHD + 2557LMT + DS61LMT-S Boston MA

not speed limits

I believe that the map database contains an estimated average rate of advance for each segment of road, not necessarily represented directly as miles per hour but perhaps as a tiered category. If it relied on speed limit data, it would have no estimate for the great majority of road segments, for which it lacks speed limit data.

Also I believe you will observe if you place your unit in simulation mode, that the speed it shows you going on any given segment of road is rather usually not exactly the speed limit.

As others have suggested on this thread, the "ER" endings which distinguish faster from shorter suggest that the difference is an adjustment of the bias with which various considerations are balanced, and not an absolute. My guess is that if you could do the detailed calculations you would find it would not send you on a 100 mile longer routing just to save one second in estimated time of arrival.

Finally, the routing calculation is far too complex to allow calculation reliably to find the single route which is truly "best" by the current weighting, especially with a rather modest processor available for the task. So what you get is a pretty good guess.

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personal GPS user since 1992

If I

archae86 wrote:

I believe that the map database contains an estimated average rate of advance for each segment of road, not necessarily represented directly as miles per hour but perhaps as a tiered category. If it relied on speed limit data, it would have no estimate for the great majority of road segments, for which it lacks speed limit data.

If I understand what your saying correctly I would have to disagree. The actual speed limit of a road must be in the map data somewhere. To me this is evident by the fact that the speed limit displayed on the map screen will most often change within feet of the actual change as shown on the highway sign you just past.

Now if your saying that the speed limit data isn't used to calculate a route but only the road category then that is probably true.

--
Nuvi 350, 760, 1695LM, 3790LMT, 2460LMT, 3597LMTHD, DriveLuxe 50LMTHD, DriveSmart 61, Garmin Drive 52, Garmin Backup Camera 40 and TomTom XXL540s.

This is so true.

t923347 wrote:

There is no setting for Shortest Time. There is a setting for Faster Time and one for Shorter Distance.

In either setting it's possible that you'd get 2 different routes coming and going to a specific location. The Nuvi takes into account many things when calculating a route so depending on things like what advoidances you have set, how may left turns are involved in your route (take longer than right turns), etc. the GPS will often find a different route between points A and B than it will between B and A. Sometimes that different route doesn't seem like the right one to us. laugh out loud

Last week we took a trip to San Diego from IE. The GPS gave us different routes on the way back home.

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Nuvi 2450LM

routing

I'm a bit disappointed with Garmin's routing also. When I visit my parents it will send me on a route that is 30 minutes longer than the route I take. This is after trying all three settings. It also prefers back roads over 4 lane highways.

no device

jfulton wrote:

I'm a bit disappointed with Garmin's routing also.

No device will make the same choices a human would do every time. Going back through the archives of discussions here on POI-Factory routing is probably the most discussed topic outside of traffic cameras. The most effective solution remains use 2 things consistently. One is quite common, the other seems to be becoming more scarce as we seek technology.

It's been stated many times to review your route before starting. The best way to review your route is by using something that allows you to see the entire route with sufficient detail and that can only be found on the ubiquitous road map. The other item growing more scarce with each iteration of technological wizardry is common sense. Failure to use either isn't the device's fault, it falls squarely on the shoulders of the operator.

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Illiterate? Write for free help.

I AGREE WITH

Box Car on this. Just use a little common sense. Don't depend solely on the GPS. Remember it is just small computer. Preveiw your route before you leave on a trip or anywhere you plan to go.

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3790LMT; 2595LMT; 3590LMT, 60LMTHD

Is Mapquest any better?

jfulton wrote:

I'm a bit disappointed with Garmin's routing also. When I visit my parents it will send me on a route that is 30 minutes longer than the route I take. This is after trying all three settings. It also prefers back roads over 4 lane highways.

One of the thinks I do to check out a route I have planned with a GPS is to see what Mapquest would suggest. The reason I do this is because Mapquest will often give alternatives. There might be a reason that I would like to go through X rather than Y on the way.

Would love to know if your preferred route one of the Mapquest options?

Routing not the Greatest

I have occasionally found that the route provided returning from a destination is different than the one provided going. Doesn't bother me though. After using the GPS for 15 years I've gotten used to ignoring it when convenient.

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Tuckahoe Mike - Nuvi 3490LMT, Nuvi 260W, iPhone X, Mazda MX-5 Nav

we disagree

The girl living inside my GPS obviously has not driven around Kentucky and Tennessee as much as I have and we frequently disagree on the best route.
At least it gives me some one to talk to

Funny

k8doc wrote:

The girl living inside my GPS obviously has not driven around Kentucky and Tennessee as much as I have and we frequently disagree on the best route.
At least it gives me some one to talk to

ha ha

who?

k8doc wrote:

The girl living inside my GPS obviously has not driven around Kentucky and Tennessee as much as I have and we frequently disagree on the best route.
At least it gives me some one to talk to

Oh, you mean the B***h in the box. But she can be quite the hoot as she tries to pronounce street names.

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Illiterate? Write for free help.

routing

Box Car wrote:

No device will make the same choices a human would do every time. Going back through the archives of discussions here on POI-Factory routing is probably the most discussed topic outside of traffic cameras. The most effective solution remains use 2 things consistently. One is quite common, the other seems to be becoming more scarce as we seek technology.

It's been stated many times to review your route before starting. The best way to review your route is by using something that allows you to see the entire route with sufficient detail and that can only be found on the ubiquitous road map. The other item growing more scarce with each iteration of technological wizardry is common sense. Failure to use either isn't the device's fault, it falls squarely on the shoulders of the operator.

Let me expand this with a great real life example. A few years ago my bride and I went from the DC area to San Antonio to visit with friends. We used Mapsource to plan the route and put in enough shaping points to follow the Interstates rather than the more direct route that would have taken some secondary roads. Everything went according to plan until we approached Dallas coming in from the East. The route I transferred from Mapsource had us on 635 around Dallas but that's not what "Gertrude" decided was best. She wanted to go straight into downtown and then south on I-35 not bothering with I-635. Because I knew I was to take I-635 I knew to ignore the B in the Box and swung across 4 lanes to hit the exit. My only error was in not insuring I-635 would be used by using a shaping (via) point to force the route. But, because I had planned the entire route and knew which roads I was to take, I didn't get trapped in mid-day Dallas traffic.

You always need to remember, when you plan a route, even using Garmin's tools such as Mapsource or Basecamp, the Nuvi ALWAYS replans the route based on the points you feed into it. It's never the same route as shown on the computer unless you have added enough shaping or via points. The Nuvi always routes from point to point each and every time you tell it to plan a trip.

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Illiterate? Write for free help.

THAT HAPPENS

To me every time I am going east on I 30. I want to take I 635, but no, GPS wants me to go through Dallas. Lucky I know that I635 will take me to I35 to Austin.

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3790LMT; 2595LMT; 3590LMT, 60LMTHD

of course it has (some) speed limits

t923347 wrote:

If I understand what your saying correctly I would have to disagree. The actual speed limit of a road must be in the map data somewhere

Agreed that for many segments of many roads the database has a speed limit value--which I see on my display as you do on yours. But what about all the other segments of roads for which no speed limit is displayed? Do you suppose it is in the database but that Garmin chooses to hide it from direct display?

I never said it had no speed limits--just that I thought it not to use them for the rate of advance assumed for route calculation and ETA, etc.

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personal GPS user since 1992

shortest

uber360 wrote:
GAJohn wrote:

Shortest Time Routing?

My nuvi 1450 has three modes:

Faster time
Less fuel
Shorter distance

I think you've got to be cautious using the Shorter distance mode - - it can be a serious time waster.

I'll never forget a story a friend told me when he got his first GPS years ago. He and a friend were traveling from Miami to Boston and it seemed logical to him to set the device to "shorter distance" and they were off! It took them 1.5 days of travel to reach the Georgia border using that mode sad

I was in Missouri one time and picked shortest route and I think the GPS had me on every gravel road in the state even though I had it set to avoid gravel roads.

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Anytime you have a 50-50 chance of getting something right, there's a 90% probability you'll get it wrong.

Set up route on Google first?

I'd heard about this. Tried set up route I wanted on GG then imported in to GPS but didn't work?

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Nuvi 2450LM

Google.

Google Maps do not support direct route transfer to a Garmin. Mapquest does.

It can be accomplished with Google, but requires a third party plugin or app to convert the Google route into a Garmin compatible GPX file.

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Alan - Android Auto, DriveLuxe 51LMT-S, DriveLuxe 50LMTHD, Nuvi 3597LMTHD, Oregon 550T, Nuvi 855, Nuvi 755T, Lowrance Endura Sierra, Bosch Nyon