HMR said:
You can never use the 2610 (nor any other Garmin) to automatically route on the roads you prefer to drive. Forget it once & for all! It can only route fastest or shortest road to the goal. The settings of various road type preferences seldom work for several reasons...
HMR:
I'm not so sure your rather definitive and exclusive statement is correct. I think a better way to express it would be as follows:
Both the GPSR and the MapSource application give the user a fair amount of control over what roads are chosen when a route is automatically generated. By default, the GPSR and MapSource are set up to route the vehicle either the shortest or fastest way (as chosen by the user), subject to the following variables that the user can also impose:
1) Area avoidances
2) Street avoidances
3) Vehicle type related criteria (truck, car, bicycle issues)
4) Specific road attribute avoidances (e.g. toll roads, unpaved roads, highways)
5) Preferences for or against three rather broad descriptions of road types, those being major, medium, and minor.
I don't know what the algorithms used for route calculation are, and I don't know what trade-offs get made when a route is calculated. One thing I do know is that every one of the 5 factors listed above is will be negotiable if no other routing possibility exists. For example, if you say you want to travel from London to Paris, but not on toll roads and not on highways - hey, you are going to get a route that includes both toll roads and highways, simply because there is no way to get across the English Channel free, and there is no way to get in and out of the ferry / tunnel system without travelling on a highway.
Please appreciate that the software engineers didn't want either the GPSR or the MapSource application returning a message to the user that said "Sorry, I can't do it" when they asked either the GPSR or MapSource to calculate a route - you can imagine that there would be hell to pay if users started seeing that kind of message as a result of strict and unyielding adherence to user criteria for route generation. So, when you look at it in that context, everything is a 'preference', nothing is 'absolute'.
On the other hand - if the task you set for the generation of the route is fairly straightforward, either the GPSR or the MapSource application will generally do a pretty good job of complying with your wishes, provided that your wishes are not contradictory in nature. As you can appreciate, with the literally unlimited number of possible computational challenges that need to be addressed as the route calculation engine works its way through the cartographic database, the rationale behind the results you are eventually presented with is not always immediately obvious to the user. This can cause an inexperienced user (or, perhaps, an experienced user who is prone to making sweeping, blanket pronouncements) to say "Hey, the routing engine doesn't work as advertised".
I rode over 30,000 km some years ago testing and helping to fine-tune the Advanced Routing Preferences feature. This is the feature that allows you to give priority (or penalty) to the use of the three broad categories of roads when an autoroute is calculated - point 5 in the list above. I think it needs to be pointed out here that Garmin included that feature
specifically as a result of requests from motorcycle riders.
What I found when I was testing that feature was as follows:
1) It works best if you are always outside of large cities. An absolutely ideal environment for using those three preferences would be a trip from (for example) just south of Lyon, France to just north of Avignon, France. If you set that kind of route up on your GPSR, and asked it to avoid major and minor roads but give above-normal priority to medium roads, you would enjoy a most pleasant trip down the
departmental roads of France, passing through numerous small villages along the way.
2) It really doesn't have much affect on the generation of a route that goes through a large city - for example, a route from Hempstead, England south to Croydon, England. In such a case, the routing engine has to give so much attention to other factors in the dense urban environment that it really has very little attention to pay to trying to construct a 'scenic' route. Heck, it has a full time job just trying to get you through that huge urban agglomeration in the most efficient manner.
3) The major-medium-minor preferences work best when used on a series of fairly short calculations (e.g. 100 mile trips), rather than on a single huge route calculation (e.g. a 1,000 mile trip). This is because the longer your route is, the greater your likelihood of having to go through a large city.
4) One area that this preference capability really, really shines in is the ability to keep you on the kinds of roads you want to ride on when you are simply 'poking along' in a general direction (e.g heading to the south of France for a week, in no particular hurry) and you are constantly deviating off route to the left or right to explore interesting things you see along the way. Under these conditions - dynamic route recalculation in non-urban areas - it really shines. Heck, you don't have to spend all winter planning your route out in great detail, and loading 50 little route segments into your GPSR and then slavishly adhering to them - you just head in the general direction you want to go in, figure your own way through obstacles such as larger cities or 'bottlenecks' such as ferry crossings, and then enjoy dynamic autorouting that keeps you on the type of roads you prefer 90% of the time.
Like anything else in life that is not 'pure black and white', you need to learn by experimentation in real life (meaning, using the GPSR, not MapSource) how to best use this feature. If you spend a few days fooling around with it, adjusting the criteria up or down and learning what effect that has on the roads that are selected for your consideration - then, you'll soon become aware of what this feature can and cannot do for you, and you will then be able to use it to your best advantage. I use routing preferences all the time when I am doing long distance travel for pleasure (not simply for transit), and I am quite happy with how well it works. It's not perfect, but it does make a significant difference to the types of roads that are proposed to you for your route.
Don't forget that if you don't like the road ahead of you that the GPSR has proposed, you just look at the map on your tankbag, head down a different road that is more to your liking, and then see what the GPSR will suggest to you next, once it realizes you didn't like its first proposal.
Michael
As always, don't forget the following advice:
...anyway, if it is on, and an unpaved road comprises part of the shortest route, the GPSR will calculate an alternative route that uses hard surface roads only, and this will probably be a longer route.
