Faster Route?

Does the 255W have any Avoidances set? Avoiding highways or tollways could cause this. Using the GPS in Bicycle or Pedestrian Mode rather than Automobile mode could also send you to smaller roads. It doesn't sound have you have Traffic on your 255W but a traffic issue on what may be the normally fastest route may detour you onto smaller roads.

Check your avoidances (Wrench > Settings > Routing > Avoidance Setup) and make sure something in the list is checked that shouldn't be. Example: on Garmin Mobile XT (which uses the same general setup as the 255W), I have set the following avoidances:

Carpool Lanes
Ferries
Traffic
Unpaved Roads

You may have more set than you expect. Without a traffic receiver however, the GPS won't take traffic into account when it comes to calculating a route.

For tips and tricks: http://home.comcast.net/~ghayman3/garmin.gps/pageinfo.htm

I frequently see the nuvi pick both slower and longer routes over what I know I should do. In one case it will tell me to drive out of my way, on a route that has three additional red lights and is longer. When I know that I'm going to go the way that I want I switch to the dashboard mode and watch numbers as it says "recalculating". My chosen route in this case is 4 minutes faster and a mile shorter. Clearly the GPS knows about these roads since it quickly figures out the better numbers, but it always fails to pick that route. I've seen this many times on local routes.

Of course, I've used the GPS on routes where I didn't know all of the local roads. It got me where I wanted to go, and the trip was much more enjoyable with a GPS than trying to work with maps. But I don't kid myself that the nuvi is always taking the fastest or shortest routes. I know that it does not in areas that I know well, so I have to assume that it makes similar poorer choices in areas that are new to me. But it is likely no worse than sopping frequently to check a map or driving with the steering wheel in one hand and a map in the other and occasionally having to backtrack because of a missed turn.

it was be nice if Garmin had a "most use of interstates" feature to pick.

Frovingslosh I agree with you, most of the time my Nuvi will pick a different route than I would on known territory, however I was pondering why it does that? Here is the conclusion I came to.

If I want to go from point A to point B on a route I’m familiar with and I ask 10 different people they will probably give me a bunch of different ways besides the one I would choose so the GPSr is no different.

Back in my younger years (way before GPS) I drove Yellow cab in Philly for about a year, I knew the city pretty well but seldom started to drive before asking the customer if they had a preferable way to the destination, the majority of the time their way meant bigger fare for me since I knew the shortcuts.

IMO the GPSr shines when you don’t know the way to San Jose…

I see these same things. I wonder if we are expecting too much from our GPS receivers. How could they know how long the traffic lights sit on red? Sometimes I see variations in timing at the intersections. A few weeks ago, on my normal route to home, one of the red lights barely let three cars through in my direction. This lasted about two weeks, and just about the time I was annoyed enough to think about contacting the city,they fixed it.

Our GPS units can't possibly adjust for these types of things with today's technology.

On the other hand, most of the time, at least in my own case, it gets the shorter time calc correct, despite what I think is right.

I usually use fastest route when on the road, but I use the shortest route setting when around home. I could understand slightly if the nuvi had a different concept of fastest than I did, particularly since it seems to have no idea that red lights can take time to stop at them. But I see the nuvi make wrong choices even when in shortest route configuration. And, as I said above, the nuvi knows the distances and quickly recalculates and indicates a shorter distance to destination when I turn off the suggested route.

All that I can conclude is that the programming is sloppy, and while it does usually find a route, it often doesn't really find the shortest or fastest route.

I leave mine on Faster Time.
If I choose the Shorter Route, it has tried to take me off an Interstate to cut through back roads and then put me back on the same Interstate again.
This route was chosen because it was 1 mile shorter. But it would have taken me 15 minutes longer because of the stop lights.

I find this happens when the GPS is receiving traffic reports (that may be wrong). It seems to set the route when you start. If it's got a report of a traffic holdup, it routes you around it (if you've got this set in avoidances). Problem is, the traffic reports are often erroneous so it's just a bad route.

I quit using traffic avoidance here in my home town. My "feel" for traffic is more accurate than the reports.

GPS is still evolving and while it is a giant leap now, I am sure it will get better each year. They have already added the speed limit feature which is another variable. When that type of data is incorporated more into the computer analysis, I think the accuracy of route selection will improve.

By the way, I think the speed limit reporting is one of the best new features to come about in a few years.

It would be nice if Garmin would add a scenic route.Some of the newer GPS out (Garmin Nulink 1695) and coming out spring 2011 the TomTom 2505 M are internet enabled which allow you to get almost instant updates and better routes.

From time to time I will compare the fastest time to the shortest distance. For example, my bother-in-law lives approximately 90 miles from me. When I compare fastest to shortest, the fastest time is usually 1-2 minutes faster, however, it is also 12 miles longer. (The fastest time uses interstate highways as opposed to using secondary roads for the shortest time.) Therefore, I will always use the shortest distance when I use the GPS in traveling to his house. Sometimes it pays to compare the times vs. the miles to be driven.

I always pass-by this "mistake" and my unit recalculates the proper route . I do agree that maybe the route avoidances aren't set up properly !
I am amazed at how accurate the ETA time really is !

I do have avoidances enabled. I have set the following:
U-Turns
Traffic
Unpaved Roads

The route that I am noticing is the most as not being the fastest route is going through town to my home. The GPS wants me to go on smaller roads (slower speeds) which are actually longer time. I know this because I have traveled this route for many years!

Should I include other avoidances or unselect any or is this just something that is a limitation of the GPS?

I am still trying to get this figured out. Thanks!

I would try unclicking "traffic". The nuvi may be picking secondary roads thinking they will have less traffic. Maybe.

I agree with the other comments that the nuvi's best use is when you do not know where you are going. It gives you a way to get there (in the vast majority of cases) but not necessarily the best way. The times ignore the number of stoplights and I suspect the routes it picks do too. If I were to pick one thing for more attention it would be having the nuvi not ignoring stop lights.

The other thing I would note is if you just ignore the nuvi's directions it will "recalculate" sometimes understanding where you are going and get on-board. Sometimes it just seems to get hopelessly confused, however.

Jim

Sixeye, you hit a bullseye!!!!!!!

As amazing as a GPS is, it really can't know the traffic patterns for each and every road, and section of road, to make the determination as to what will really be the fastest, etc.

the GPS does not have local knowledge. What it knows, is the speed limit on the various roads and the distances. It does not understand road conditions, traffic issues, number of stop signs and lights. So, at times, it will select a sub-optimium route that a local would know not to select.

I have been using GPS for 6 or 7 years now. i believe the programming also involves limiting the number of turns to minimize confusion so shortest or fastest might be differant form your known better route to keep it simple.

The reason that I question this is that the GPS does know some things, and they should be enough to make a better choice, at least when "shortest distance" is selected. Yet I can watch my nivi dashboard when I choose to turn off the nuvi's suggested route and onto my selected route, hear it say "recalculating" and then see it display a significantly shorter distance to destination (and a better ETA). I don't know of any way that you can excuse this, the nuvi knows that the route I take is shorter, and it knows the turn I took is there, so only sloppy programming can explain the longer route it keeps trying to direct me to. This is more vague when "fastest route" is the selected option, but since the behavior is pretty much the same, I'm inclined to not make excuses for my nuvi and simply attribute the same degree of poor coding that I see exhibited with the shortest distance option.

Thinking about the example that I use above, that could well be the case, as the longer route that also hits more traffic lights does indeed involve one or two less road changes. But I really can't excuse it for that and trying to "keep it simple", certainly not on the shortest distance setting. I don't need or want the GPS to treat me like an idiot who can't deal with an extra turn and take me a mile out of my way, after all I'm using a GPS that can give me voice directions at every turn. This isn't the last millennium's printed "trip tick" technology.