Poor Garmin route?

What are the settings you have in your GPSr ?

1. Fastest or Shortest Routing ?????

2. What avoidances are set ??????

The GPS does not have your local knowledge of the area. You know the best, most efficient route because you live there. The GPS does not. I think you will find the GPS will do its best to keep you on the major roads connecting two points. What may seem like a good route to you locally may be made up of some roads that have a secondary road classification. The GPS will route you via a highway before it will send you through residential streets.

I calculated the two routes on my MS Streets & Trips software. Your route was 9.6 miles, 21 minutes estimated driving time. The GPS route was 12.4 miles , 22 minutes estimated driving time. Based on the map information the GPS uses to calculate the route, it probably made the best choice for you. It was slightly longer than your route but the estimated driving time was only 1 minute longer. ...and the GPS kept you better rated highways. Personally, I find that comforting. If I am in a strange city, I don't want the GPS sending me off a major route through what could possible be a bad area.

If you change your GPS settings to avoid highways and select the shortest distance, It just might come up with the same route you prefer.

Yeah, the GPS will try to always keep you on the main roads, or the knows roads. I went offroading into a dessert once and all I got was a straight line to the main road. No local shortcuts or anything.

venture into the Sonoma and Napa counties of Northern California if you expect to have your GPS route you along the freeways. My experience with a Nuvi 660 is just the opposite. It will route you along secondary roads completely ignoring the paralleling freeways. On a recent trip from Fresno to Santa Rosa it sent me from 99 to 120 to 205 to 580 to 680 to 780 to 29 to 37 to 121 and onto 12 leading into the back side of Santa Rosa.

I normally travel to that same area by going from 99 to 120 to 205 to 580 to 101. All freeways.

Incidentally, I have the thing set on "Fastest route".

I programmed my C530 for Fresno to Santa Rosa and it selected all freeways. Are you sure you did not have your avoidances enabled to avoid highways or toll roads?

is U-turns and Unpaved roads.

The unit's programming is biased to major roads, or at least my unit is. I've seen it route me to a major highway, more miles and avoid a shorter & **quicker** route - by it's own calculations.

For example, near my house, I selected a destination - it routed me to a major highway and calculated it would take 21 minutes. Upon leaving my house, I immediately went a different direction and the new calculated route was one minute quicker, but used "lesser" roads.

The GPS will definitely get you where you want to go - optimium routes? No, not usually. Do I use my unit much - yes, all the time. Just because it is not as smart as I am concerning local roads doesn't mean the unit has no value!

When I bought my first unit about 9 years ago, I waited because I wanted downloadable routes and maps.

My second unit - I waited until the battery life was better and the map memory expanded so I had enough maps on the unit to go where I wanted.

My third generation unit - I waited until it had voice instructions and automatic routing.

My fourth unit - which I'm waiting on - needs more intelligent routing. Until then, I'm happy with what have and see no reason to buy another.

I'm a new user and find that often the route selected seems to avoid freeways - is that dependant on range?

i have no avoidances set and fastest selected

c330

if you know where you're going why don't you go the way you want and have it recalculate the route for you?

I was working another forum on this site and the subject of vehicle selection came up. I thought it was the vehicle icon on the map screen but there is another vehicle selection that has to do with route optimization. ( of course, the manual doesn't mention this at all )

On my nuvi 650, there is a vehicle choice under "wrench icon" -> Navigation -> Vehicle. I have tested Bicycle, Truck, Car and Pedestrian to the exact same destination. It is amazing how the route selection changes when I pick different types of vehicles. You might try this option also.

dd

I cant count the number of posts on this site and other sites regarding poor route calculation. From what I've read I believe there is a software issue that needs to be addressed by Garmin. I myself experienced bad routing on a recent trip from Williamsburg, Va to my home in N.C. There was a major interstate that the Nuvi should of taken me home on but instead it routed me on a two lane highway for 60 miles before putting me on the interstate. I was in no hurry so we took the two lane road, man what a mistake! Traffic, draw bridge, and many turns. My avoidances were only unpaved roads, and set for fastest route. The way I currently get around this occuring asgain is by inserting a waypoint or just force it into a recalculating mode by driving the way it should take you.

There is a Garmin Technician that occasionally posts on this site. Maybe he can give us all some guidance with this very real and annoying problem many of us have with the Garmin routing engine.

I put my Nuvi 660 into simulation mode and asked it to come up with the, "Fastest route" from the corner of Herndon and West in Fresno,California to the middle of Winnemucca, Nevada. It told me the best route was to run up highway 41 into Yosemite national park and then take highway 120 over to highway 395 and north to Carson city and north to I-80 then east to Winnemucca.

That might be a fine route if you are in an F-16, but the most logical and by far the fastest route is Highway 99 to Sacramento then take I-80 east to Winnemucca.

I think the boys over at Garmin need to rethink their navigation engine. I'm going to tour the Southern States this fall and now I'm concerned that my Nuvi won't have my best interests at heart.

I'm having similar issues with my Garmin 265WT. I'm pretty tech-savvy, and have been using various GPS devices for 10+ years. My Garmin prefers to put me on local roads (stop-lights, etc), vs highways and interstates. I travel a lot for work, and I've noticed this problem in several parts of the country, and not an isolated incident. I assume the algorithm calculates the route by multiplying the distance by the posted speed limit. What bothers me is that if it is even close, the device should send you on an interstate. We all know that driving non-stop, is always better than stoplights, stop signs, etc. My Garmin will even do things like send you off an interstate onto local roads for a bit, and then send you right back on the interstate. At first I thought this was due to expected traffic, but the traffic on the local roads has been worse than the clear interstate.

I have it set for "fastest route" and nothing for avoidance's. I wish they had a "maximize interstate" setting. Some one needs to look into the programming, and bias it towards divided highways. I really like all of the other functions of my Garmin, but the poor routing is really frustrating!

I had a great experience nearly two years ago renting a car for a week. The Garmin seemed to efficiently route me to most of my destinations. Although, noting: I would type one destination at a time, not using Routing Optimization of multiple destinations. I bought the Nuvi 1450 a year ago, but just now getting a chance to try out the Route Features with multiple destinations.

1) I read long ago about using Streets & Trips and import into Garmin. Garmin Tech support was no help. I read many forums (entire days work) and figured out that I had to convert the gpx file (for whatever reason is incompatible) from streets & trips using a product called Extra POI Editor, then import into Base Camp to then import into my Garmin Routes. Hardly seems worth it. I'm in sales and trying to map out about 2000 businesses in the Streets & Trips software creating many zones or Routes per each day, which is a lot of work but helps me to not overlap visiting the same businesses by accident.

2) I just tried out 25 destinations last Friday. The Garmin sent me all over the place here and there, overlapping the same roads; very inefficient.

3) Garmin would make me drive way over into parking lots and side roads to satisfy reaching my destination, which was inconveniently inaccurate and annoying.

4) I also would encounter that Garmin could not find a road or the business I'm trying to find, and I would simply like to skip at this point, but still proceed with the next business to visit. Instead, it seems my only option is to cancel my route, then access the Route, and then delete all locations I have already visited and the one Garmin can not find, then tell it to configure new route from current location. Annoying.

5) I now discover in Google Search of Garmin bad routing, way too many forums including this one, complaining about bad Routes from Garmin. Very disappointing!

6) One extra side note that made this first experience worse is that, although this was in my home town, I was unfamiliar with the specific in-roads and it was the very worst and most dangerous part of town. This part of town is probably high national crime rate, here in Waco Texas. I'm not racist, but I know that white guys in a nice tie are not welcome in this part of town and I received some very concerning looks from some individuals on the streets that I was not supposed to be on their turf. Gamin kept putting me in some seemingly very dangerous situations and made no since or need to take these choices of roads.

All this to say, I don't want to give up on my Garmin and Sales Route Concept, but very disappointed so far and not sure it is worth it to proceed.

Garmin routing is poor. I frequently find that it will take me far out of my way and into denser traffic when there are shorter and faster ways, and that it can calculate the shorter and faster route once I turn onto it indicates that it does have all of the necessary data in its database, it just doesn't use it wisely. I have also seen many times the failure that you noted about not taking the shortest and most direct to a destination. Many times it has taken me a mile or more down a divided road and then had me make a U-turn and come back, when it could have just had me make a left at the intersection before my destination and enter by a side street parking lot entrance.

My nuvi doesn't actually do routes but I can accomplish about the same effect by adding "vias". But one still needs to learn not to trust the GPS and to go by instinct first and only use the GPS when you need more information.

I doubt that political correctness will ever let us have GPSs that avoid high crime areas. Again, use common sense. Would you drive into a river just because the GPS told you that a road was there? Sure, tourists in Miami might die when they take the wrong exit off the freeway because their GPS sent them there, but the GPS makers are happier with that then with being labeled racists for marking high crime areas in their data and giving their customers an option to avoid them.

No matter what settings I use I always get poor routes.

Had a problem with my GPS routing me where I didn't want to go.

I've found the same thing with the Santa Rosa area. I would drive to Santa Rosa for work from time to time and my nüvi 760 would always want to route me on the secondary roads. It's more scenic but the freeway was soooo much faster and more efficient --- EXCEPT during high traffic times. Then the freeway was horrible. I too have my unit set for Fastest Route and the only avoidances I have set are Unpaved Roads and Carpool Lanes. I always thought it was really weird that the GPS didn't want to route me on the freeway.

ChadC writes

Good luck with 2000 waypoints. I gave up on routes with my 14xx Garmins. I have a custom POI of all the county court houses of a few states. I tried Mapsource and my 1490 to plan a route to visit all the court houses in Iowa. Both efforts came up with a lot of backtracking and poor routes. My solution was to use a road map of Iowa and common sense. I labled each county location with a number in the order. For example:
1Muscatine 2Scott 3Clinton 4Jackson.
When we do the tour, I will navigate to each one individually. This method has worked for me quite well when taking the scenic roads to Florida each year.

Chad, you are working with what is know to be a very hard problem to solve - called (as you know) the TSP - Traveling Salesman Problem. Many mathematicians spend their career trying to come up with solutions, so it is little wonder that GPS units do not do that great a job.

As spokybob just mentioned, common sense should prevail over the multitude of algorithms that are inherent in the GPS - where such algorithms often become illogical when used in real world situations.

For example

My unit does this to me and I discovered that it is likely a problem with the road being designated as a "divided highway" - you know, one of those where the only authorized left turns are for police cars. If the road were simply a 4 lane highway (which is becomes at the u-turn) all the way, then the problem would go away (and at one time it was truly a "divided" highway).

The point is that the GPS cannot see what we see on the ground. It does it's best with what it has.

Clearly we should not expect a GPS to solve the TSP (certainly we would not want to wait for it to do the brute force attempt at trying every combination and then choose the solution with the shortest distance (or did we want fastest routing?).

We would typically ask you for what "avoidances" you have set because that impacts what the unit does in certain situations. I assume you have the newest map because sometimes problems are corrected by people reporting them to Navteq and the map detail improved.

I guess if I were doing a set of calls this week, I would first clear out my "recently found". Then for each destination, I would enter all of them all as if I were about to navigate to them but when, for each, all the address/intersection/etc was entered I would just back out to the main menu and do the next one. That way I would have all of the destinations available to me later in "Recently Found".

I would then try a route under "Custom Routes" and see what the unit would do. It would at least give me a starting point for me to consider. Because the points were in "recently found" I could fairly quickly move destinations until I was reasonably satisfied.

On a recent trip from Northern KY to Roanoke, VA Garmin wanted to route me through Ohio. The return trip with no changes in settings the Garmin route was a much more Southern route through Lexington. After arriving back to my starting point and putting the original Roanoke destination into Garmin it selected the more Southern route through Lexington. Why two different routes with identical start and end points and no changes in settings? The only difference was the day of the week, and I don't see that making a difference.

Are you saying that the coordinates of the unit when you pressed "Go" at the start of the trip were the same as those of the destination for the return trip?

And, were the coordinates of the original destination the exact spot where you were when you pressed "Go" to start the return trip?

Being a motorcycle touring person, two riders on two bikes with identical GPS, riding together, going to the same Waypoint or POI, can have different turns and routes to that Waypoint.

Why...in part each GPS may be programmed differently with method of avoidances.

If the route was created and downloaded from BaseCamp, the route would depend whether it was a PROFILE route or a CUSTOM route.

So with this you can have five or six ways to get there.

A route planned with BaseCamp and downloaded will come closer to given you your chosen route.

Routes created on the go...by the GPS unit...you are at the mercy of that unit and how it is programmed. (a paper map is the best accessory for a GPS unit)

I personally am a Waypoint/POI person..I will have my unit loaded with EXTRAS and my favorite Waypoints. Click on the waypoint and go...with my unit programmed for my type of riding and avoidances.

It's mind over GPS, if I get to a turn that doesn't look good...don't turn...If u-turns are checked as avoidance, then I will get there... It all an adventure!

Also, I like BaseCamp for planning...all the data is before you..if you have it set to your organization of Folders and List. Thanks to his forum, my resource folder has 22,000 plus waypoints in numerous list. In a couple of classes I have taught with fellow motorcyclist...I use that many waypoint to show the power of BaseCamp and how to migrate the data to planning folders and list.

In regard to 2000 customers, I would suggest a folder for each city or state and then a list for each region or city or type of business account.... Then I would create a route for each day with only the contacts for that day.

Hope this helps...

My theory, based on complete lack of evidence, is that the problem goes back to the source of the map data. I believe Garmin buys maps from third parties who assemble them from GIS data purchased from local jurisdictions. The local government has no interest in improving Garmin’s routing, so they don’t care if some data elements are missing.

My deduction for Baltimore is that travel times through city intersections are assumed to take zero time. It’s as if the lights are always green and there is no traffic. Given that starting point, it does compute faster to go through the city than the longer distance on the interstate that circles the city. Of course, some of those city intersections have traffic light cycle times approaching 5 minutes which really slows you down. In addition, the Beltway seems to average closer to 70 than the posted 55, so on a good day you can gain time on the interstate.

No facts of course, but this theory does seem to agree with observations.

I agree with you. I believe that traffic lights and stop signs do not cause any delays. It assumes that you either have all green lights or you drive right through reds and stop signs. I've watched many people blow through Reds and Stops. I have to assume that some of them must be the Garmin Routing Software people and they assume that everyone drives like them.

I don't think they use the posted speeds, for roads. Specific types of roads have a set speeds, such as 65 MPH for Interstates, 60 MPH for Major Highways, 50 MPH for Other Highways and 30 MPH for streets. These are only guesses.

It's impossible to account for where traffic lights and stop signs are located, and even harder to assume duration.

It might be better if you could Customize your speeds in the GPS, to get a better approximation, that might closer match your own driving and to allow for lights and stop signs, where they might exist.

There certainly could be some issues with the map data that causes some of the failures we have seen (particularly those U turns when the destination could be entered from a side street instead), but there is plenty of evidence that the data can be good and Garmin will still make bad choices. In a case that I see frequently around my home, the GPS is set to "shortest route" but the nuvi will always route me a longer route that includes more traffic lights, more mileage, and more traffic. But it knows that the shorter roads are there, the right turn that I take to avoid the poor route shows on the map, and as soon as I make the turn the nuvi says "recalculating" and then the dashboard shows both the remaining distance and remaining time drop. Can't really blame the data there, it is simply a failure to consider the option.

If you check the estimated arrival time immediately before and after the recalculation, which way does it change? Frequently, the estimated arrival time after the turn is later (or the same). That would indicate that the GPS made the correct decision based on its map data.

I have also noticed that when driving in a town with red lights, the estimated travel time seems to be dramatically short. The estimated arrival time holds pretty constant when driving and slips away minute by minute when stopped at a light. More good evidence that the map data is not accounting for any red light delays.

If you picked a different destination, would the Nuvi route you through that right turn? Most likely it would, but there does exist the possibility that the turn is not routable with their map data. I have never noticed that on my Nuvi, but I do know that Google Maps will refuse to route me onto a road that I frequently use.

I am not saying that the Nuvi always chooses the “better” route. Efficient routing is a hard problem, so I do believe that on occasion the better choices get missed. But on mine, the indirect evidence seems to indicate that the under lying data is more often suspect.

I tried to make that clear, but let me try again. When I am traveling locally I set my GPS to shortest, not fastest, so time really should not matter. None the less, when the GPS does it's recalculation it shows that my route choice is BOTH shorter and faster. And it is even faster, since the GPS assumes that you'll never spend any time stopped at a traffic light and there are more of them on its chosen route (three versus one, plus when I rejoin the nuvi route I get to make a right turn on red where the nuvi route often stops me (going straight) at that red light too). I could forgive the nuvi for its bad traffic light choices, but the GPS is set to shorter route and it just ignores the shorter route. That's a failure.

I could sort of understand IF the right turn that I made wasn't recognized as faster immediately but only after I made some better decision later. Then one could argue that the nuvi checked the route, found it longer and didn't look deeper. But this turn is an obvious turn that any route comparison software should check, other than just "wanting" to keep me on busier, more traveled roads (more traffic) I can't see any reason why the nuvi should take its choice.

This is just one example, there have been many times when I know an area that I take a different route that is much better than what the nuvi wants to give me. Of course, I've used the GPS in areas that I'm not familiar with to route me to a completely new location or to route me on more interesting back roads rather than to take the same Interstate route that I've taken many times before. It has gotten me where I want to go. But since I know that it makes bad choices when I know the roads, I have to assume that it may not be making the best choices for me when I don't have good knowledge of the area.

One of the classic routing algorithms is call A* ( A star). The Wikipedia page is http://en.wikipedia.org/wiki/A*_search_algorithm and there is a useful short write-up at http://www-cs-students.stanford.edu/~amitp/Articles/AStar2.h... . I have no idea if Garman actually uses A* but it is likely they use something like it.

Check the two motion graphics on Wikipedia. The first shows an exhaustive search that produces an optimum answer. The second gets the answer faster but it is less than optimum. The second article talks about breaking the problem into regions when the problem is highly complex (like a real map). In this case, even if all the regions are optimally connected, there can still be better routes. Both of these cases show techniques for dramatically reducing solution time in order to get an answer that is “good enough”. I have to believe that Garmin thinks the same way. After all, a reasonable answer they can compute in 30 seconds is much more useful than taking hours to compute the true optimal answer.

The good news is for a lot of routes the quick “good enough” answer is the optimal route. But when there are multiple routes involving multiple intersections and differing road types, it is easy to believe that the algorithms for handling regions does not always pick the best choice.

Ah - a classy answer.

I believe too many people think that their $200 unit has the computing power of a super computer. I am happy that it gets me where I want to go.

I was on rt US29 between Fargo and the St Dakota line. My GPS kept telling me that there was a "better" way to go. There is no other way to go on that route. There are no other roads that cross that road but little farm roads. If you say OK, it recalculates and gives the same road.
I think they just like to annoy people!

I belive that too. I never had trouble with my GPS routing me where I didn't want to go.

I have been complaining here for over a year about Garmin messing up the routing algorithims.

Every time a new map comes out something different is screwed up with routing.

I drive 36.5 miles one way, to work. All but 2 miles are on I-64 and I-664. I leave just after 5 AM everyday. I go through 3 traffic lights at the end of the route.

When I first got my 660, it routed me the quickest way to work wherever I selected "GO" at (location wise). And it did extremely well for any other location I selected. We go to Atlantic City every now and then and from Williamsburg it correctly routed me through Norfolk and up the Eastern Shore to Rt 113 in MD and then to the ferry at Lewes, MD. That is the quickest way, although the ferry is not cheap. It is also a much easier ride as there is no "White Knuckle" driving such as on the other route up I-64 W and I-95 N. Also on the Eastern Shore route, there are plenty of places for a "Pit Stop" - lots of Valeros, Royal Farms, Wawas, etc. Incidentally, I recommend Sting-Ray's Restaurant near Capeville VA on Rt 13 (It's about 5.5 miles north of the toll booth on the Eastern Shore - Great Seafood!).

The first time I noticed that something was amiss, was on a trip to the Preakness in Baltimore 3 yrs ago. I was near King's Dominion Amusement Park (Ashland, VA) and all of a sudden my 660 started telling me to get off of 95 to avoid an accident. I had just updated maps and apparently it changed my settings to automatically "Avoid" traffic delays. The strange part was where the delay was at - 70 miles ahead near the I-495 beltway. Turned that off right away and re-routed. BTW, by the time I got there, there were no delays.

A couple of map updates later, it started sending me around the block to get to my house. It doesn't do that now, but instead it now trys to send me to work down Jefferson Ave at the 255 MM on I-64. This route is the "Shortest", not the "Quickest" as its 45 mph and lots and lots of lights. If I wait until 3-4 miles before Jefferson to select GO, the 660 will send me the correct way. Sometimes if I select GO near the end of my street it will route properly.

So, you are not alone when wondering why did my Garmin make that @*&#% stupid route.

I hope they fix it soon and then leave the algorithims alone.

Before anyone asks - Yes, I check my setting after EVERY map update.

I can confirm that the routing algorithims does change depending on the map set your using. That being said, I basically only use my unit when on holidays so if it does give me a pi..poor route I won't know as I'm not familiar with the area I'm in.

One of the reasons the Garmin doesn’t give me too much grief is that I preplan all significant trips using Google Maps. If I want a specific route, I will either set an intermediate waypoint and/or remember which way to turn at the critical intersections. The Nuvi does a good job of filling in the minor details.

One of the weird side effects is what favorites I store in the Nuvi. I don’t store very many, but about half are intermediate waypoints so that I can force the routing I want. Most of them are not to overcome the Nuvi’s problems. I just prefer the non-optimum route because I want better scenery and less stress on a long drive.

When I drove from Phoenix to Los Angeles, I had looked at Google Map to estimate the driving time and distance and printed the directions map. On travel day, I entered the (same) destination location and drove off. Closer to LA, to my surprise, the Garmin routed my off the I10 onto the CA60 but I followed it by interest (I had not peeked at the whole Garmin route before hand). Eventually I ended up back on the I10 close to my destination.

I arrived at about the predicted time, but looking back at the Google Map it was really suggesting to stay on the I10 all the way - probably a simpler solution with less freeway changes on the way.

As they say, yrmv (you routing may vary)

Then again that is not why most of us buy a Nuvi, or an Oregon for that matter

Heading to a Walmart today which was on the same road I was traveling on, it wanted me to go around the block (gotta be around a mile out of the way) instead of stay on the same road directly to the store (whaaaaaaaaaaat?!?). If that's not bad enough, heading back home and I wanted to get on the (PA) turnpike, it insisted that I go through the nearby mall parking lot instead of directly straight down the road to the turnpike on ramp.

I have a strong preference to avoid the PA Turnpike. Maybe the GPS was trying to give you some good advice.

Figured if it routed me around the block I'd reconsider stopping.

(and it DID ask me to rate it...1 star)

For me, I found turning off Traffic Trends gave much more direct and logical routing. It's one of those ideas that seems good in theory, but doesn't work well in application.

I live in the South (Alabama) and find that my Nuvi is usually very accurate in its' selection of a route. Every now and then, I get a bum steer (usually when a road that was previously active has been closed off or something similar). The routes it selects are not always the fastest but they always get me where I'm going.

my 1490 wanted to send me off I95 and onto local roads in Maine last summer, REPEATEDLY, I stayed on 95 as I know Maine and I knew the hotel was about .5 miles off 95...this happens over and over, local and out of town...one reason I switched to TT.

Garmin routing simply sucks.

That's not really correct. The programming or decision-making doesn't change. It's not updated with a map update. What changes is the data that the routing programming looks at. We can't see it on our screens but the road types carry many classifications and when those classifications change, the decisions based on that data will change.

I had one instance of this following a map update where a new connecting road was added to a T intersection to turn it into a full 4-way intersection. My Nuvi showed the road continuing beyond the previous T intersection but had me turn right, go 1 block, make a U-turn and then turn right again. Looking at the map on the computer and zooming in all the way showed the answer. The new road had not been fully 'connected' on the map so the map showed a break in the road that the Nuvi properly routed me around via the U-turn. Nothing wrong with the Nuvi's decision-making here. It doesn't have eyes and can only react to the map data, which in this case was incorrect. Reported to Navteq, the map data was fixed in the next update and the Nuvi now routes me straight through that same intersection.

As for the Salesman issue, I believe we are expecting far too much processing power from a tiny hand held device. I have used MapSource extensively to develop custom routes that defy what any level of computer would be able do on it's own. Such as a scenic road trip. Take the fastest (interstate) to get to point A, then switch to the back roads to wind around the lake and hills, turn into an unpaved forest road to get to a lookout and then back to interstates to quickly get to the next area of interest. And I want to go around the lake the long way because that view is prettier. How is the GPS expected to understand "pretty"? LOL

This is where using the full computer software comes into play. The desktop has FAR more processing power than the handheld and has many more settings for things to avoid and when it finishes the route calculations, I can view the entire route on a big screen that has many times the resolution of the handheld. Choices that do not fit what I want to do then become visible and can be manually corrected.

I then download the waypoints and route to the Nuvi and it follows my truly custom route. There are a few more technicalities to deal with, but this method has served me on road trips very well.

My point here is that although it would be nice if the handheld could do this sort of thing itself, it is not realistic to expect it to do so as fast or as accurately as the computer. Use your computer to develop and visually evaluate a generated route and then add your own intelligence to tweak what the computer comes up with.