Suppport Thread for the TND 500, TND 700 or future Rand McNally products.

I will try to explain it again.

When you drive you see a road be it concrete, asphalt, or dirt, you are seeing just the surface of the road you are on.

Maps simply cannot see what you physically are on. They are build into a Database which then are broken down into DCA's or regions. This may span across one state or many. In these DCA's the maps are broken down into segments. These segments are given many variables. These variables define who/what/how big/HazMat/STAA/Non-STAA and many more variables.

The roads are also given a "cost factor". This "cost factor" will determine if road A is better than road B for routing. In my area I have a "cost factor" of a road that is "0" which is an unknown. You will never be routed on a "0" road, but once I pass that segment then the TND does recalculate. It tries to pick several side roads that are a better cost factor than I am on, not the most direct way, but again it has to go by what is has set for in the parameters of the DB.

Any road segment is also broken down into sides of the road. One side may have different variables than the side you are on.

Now you add the Truck settings to the factor. When the router starts its "thinking" process it has to go by a set of instructions. These router instructions are tweaked for the best routing for all parts of the country. You can tweak the router to the East coast, but now routing will be indetermined for the West Coast. The router has to have a happy medium.

So based upon what your settings are and the physical location you are at, the router now determines a legal truck route since you are in truck mode. If you were in car mode the router would route you based upon what the parameters are in the segments.

Before on shortest route you used to be routed up a ramp then back to the freeway if you were in a curve. To a computer this is the shortest route. Does it make sense? Nope. So by adjusting the Cost Factor to make the ramp more "expensive" than the freeway, it now keeps you on the freeway.

Maps are not 100%. Cities, county's, and states change or modify roads or restrictions daily. Getting this info back to the source takes time and the source takes time to make the changes. Maps are not compiled daily. Due to the type of testing RM does before releasing a set of maps takes time.

It does not matter if you see 1 or 100 trucks on a side road. This does not mean it is a legal route for STAA or Non-STAA. Many cities, county's and states do not post signs for all restrictions or truck routes.

Trucks are allowed to go 1 mile off any interstate for pickup/delivery. Anything beyond that you have to go by what is legal or not legal.

Many places you go were build in prior years when Cab Overs and 48' trailers were the norm. Roads do not get upgraded all the time. This costs money, so the city's and county's have allowed STAA vehicles (53'/102") to make local deliveries. You will see signs showing local deliveries only, no thru truck routing. This usually means you are on a Non-STAA route. The TND does not see the sign nor know of it physical presence. You can change your Truck settings to 48'/96" and this will allow the router to now make a more informed decision.

If you don't like the route given, simply take the route you would like. The TND along with any other GPS will adjust the route. But, be aware you may be on a non legal truck route for your settings.

A rule of thumb. If it does not route you by your settings, then change to car mode. If it routes you, then it is a truck setting or restriction that is in play. If it does not route you then it is a map issue. Post it on the support thread and I will research it.

Not are restrictions in place are current. You may have come across a restriction that has been lifted. Based upon your set of maps you may see the restriction, but it may have been corrected in later maps. Not everyone updates the maps yearly. At truck shows I still see T5B's coming in. They are at least 5 years behind on the map set.

So all in all the TND is simply a computer going by a set of instructions and using the truck settings you have determined will try to find a truck legal route based upon the data in the segments of the map set.

Now instead of listing such a broad term "but it's routing is asinine", let's be proactive and actually tell me where you are seeing routing issues. I can work much better with information that give me something to test or look at than a broad general term.

Thanks,
Mark

 

http://www.thetruckersreport.com/tr.../251918-my-rand-mcnally-tnd-720-review-2.html

See post #18, since you posted in three threads.

Thanks,
Mark

 

When they are released. Still in testing.

Thanks,
Mark