Don't rely on Garmin RV760 LTM GPS routes.

Southbound you can access the Cape Heceta lighthouse parking lot and turn around,but as you said,if you"re northbound you're outta luck unless you can turn around at Sea Lion Caves before you commit to the tunnel. Have done that run many times with equipment from our 8' P/U to the 40' class a we have now. The last time was in June in the toad going to Heceta light and we had to wait for over 1/2 hour as they were doing work on the north side bridge.

Flapper....the problem I found is since it wanted to send me another way there was no info on the GPS to access why the 101 route was not selected. By driving the route it warned me in red a few miles before the tunnel. Had I been on a route I was unfamiliar with I may have unknowingly gone 200 miles and about a days drive out of my way. That could get old and expensive after awhile.

Tom Test....they need "The Guy" to fix it. It is better than LORAN :)

Rollnhome wrote:

In fact it would not surprise me that the tunnel on 101 near Florence is the issue.

Just did that route about 2 weeks ago - and it is the tunnel. I ignored it's advice and stayed on 101 anyway. If it weren't for rigs about my size coming the other way, I would have been convinced I was going to crash and die. The DEZL 760 gets really, really insistent the closer you get to the "problem". Turns out the unit thinks the tunnel is 11'4". And my 5th is 12'. The tunnel really is signed as 11'4"! But only on the edge on the outside of the shoulder! In the center, it is signed as 14'. So I was only going to die if I was fully on the shoulder....

Looks like Garmin got bad info from whoever provided the listings for their database.....

BTW - there is an option from the navigation screen to call up a listing of any oncoming warning areas on the route (heights, sharp curves, etc.) Don't have it in from of me, so unfortunately can't instruct as to how to call it up. I was actually pretty white knuckled as I approached, knowing there was no way for me to turn around if I had to. If I'd known about the listing, I would have been able to research the warning well before making the "go ahead" decision.

Rollnhome wrote:
There are many things I like about it, but I bought it for it's main function RV Routing. It does not do a good job of route planning. I have used Marine and Highway GPSs and always check the routes. Just saying with all the information and technology this should be a problem of the past. GPS has been around for what? 20+ years. The interstates and most roads have been around much longer. Much like Marco Polo we still need to rely on paper maps and commonsense.

The GPS satellites have been operational (full constellation of 24 birds) for 19 years, final launch of the first set was 1995.

Computerized automotive navigation, goes back to the mid 1980s using other location technologies, like radio direction finding and inertial guidance, but did not roll out to consumers until 1990 when inertial reference systems became stable enough for use in cars and costs could be brought down to a few thousand dollars. These functioned as moving map displays.

First GPS receivers for street use were shown at CES in 1998, but the modern "plan a route and talk me through it" technology did not show up until the GPS system was made available for public use in 2000, and navigation devices could incorporate a relatively inexpensive GPS receiver for location, rather than inertial systems. Actually for the talking part of it, I think more like 2002 with introduction of TomTom, followed quickly by the Nuvi with similar cost and capabilities. My earlier Street Pilot just beeped when it need to give me an instruction, which I had to read before it disappeared.

That is kind of a coincidence, as that is also when turn by turn navigation was finally introduced for pre-GPS automotive navigation systems. That first one (MASS) got locations data from wireless Internet connections, the way phones do now, but it worked only where an infrastructure was set up for it.

But the real problem with these devices, whether they use GPS or something else for location, is in the map databases. The maps have errors, permanently installed maps don't keep up with changing conditions, and we have expectations that don't match routing assumptions. On 101, the map database says the tunnel is too low for your RV, based on official information about clearances and the height information you supplied. You think it should route you that way, because you know you can make it through by keeping toward the center. That kind of information is too iffy for the routing program to deal with, when the official clearance info says the vehicle does not fit.

Paulj thanks for posting the link to tunnel.

Acampingwewillgo wrote:
I'm wondering if the pure truck GPS units do a better job of keeping you off undesirable roads....you know, the roads you wouldn't drive your car on let alone a 45 foot mh?

A pure truck GPS should keep you on "designated" routes to which big commercial truck is restricted by law. This is a much more restrictive routing that possibly used for RVs, if the RV map database is correct. RVs are generally not subject to the "designated highway" legal restriction.

There may be further point restrictions based on size and weight, in some cases. The RV mode should be catching these physical restrictions.

I suspect there is a single point physical restriction in the map database for the route OP prefers to take. The restriction may not be real, or it might have been temporary. But this is more likely the problem than any fundamental flaw in the routing algorithms, and it is something that gets corrected with map updates.

When I first got a routing GPS, it had difficulty getting me from my home to downtown, just ten blocks on a through street that goes to a three-way intersection a block from my house, and the three streets have different names. Garmin couldn't handle it, Streets and Trips couldn't handle it, Mapquest couldn't handle it. They all sourced maps from what was then known as NavTeq. DeLorme Street Atlas knew how to get through that intersection, DeLorme makes their own maps.

NavTeq eventually caught the error, Garmin got the update out first, it was a couple more versions of Streets and Trips before that one was fixed.

Another error I caught on NavTeq maps was in West Lafayette. Going north out of town, the maps had me going up one of the local through roads to turn right on Sagamore Parkway. At point I was to turn, the parkway is elevated, there is no intersection, no ramp, no frontage road. Somebody was coding the intersection points (nodes in GIS terminology) from old maps. The version of S&T I am currently using still has the error.

Not only can you not totally depend on routing programs because of map database errors, you cannot necessarily depend totally on paper maps and atlases. They get out of date as roads are changed, and they simply have errors. Maps used to be drawn from aerial photography, what is seen from the air might be different from the situation on the ground.

Additionally, published maps at one time had intentional errors for the purpose of catching copyright violations. I once tried to take a road that wasn't there in South Carolina to a town that was actually someplace else a couple miles away. I don't remember the map publisher on that one, but I got a map from another publisher that had better information for that location.

You will not find much variation in quality of map databases from brand to brand, as there are not that many companies building routing databases, most brands are buying the same maps. Different brands buy updates at different intervals, and even when you buy two different brands the same day, the vintages of map data could be several years apart.

I've come to like Google Maps because they are doing their own work, rather that buying from someone else, and they are constantly at it, running vehicles on the streets and highways to develop ground truth.

GPS units are an aide and should always be checked and used with caution. Always get a scary laugh when I hear someone got stuck on railroad tracks because the GPS told them to turn.

When you find an error like this, report it to Garmin. I've reported numerous road errors and most of them have always been corrected, usually within 6 months. Most, not all, because I'm still waiting to see the update for the last two reported.

Same goes for error with google maps.

Just remember, the more data you can provide, the easier it is for them to confirm.

Google maps streetview of the Cape Creek tunnel entrance

Last year an oversized load knocked down a Washington bridge span. There was enough clearance in the center of the lane, but a passing truck in the left lane forced the oversized load too close to the fog line, and the load damaged a bridge beam.

I wonder if Mountain Directory West has a warning about this tunnel.

Or http://www.lowclearances.com/?

Well I drove the 101 like I have done many times. The reason for the Salem Eugene route WAS the tunnel near Sea Lion Caves. Though the center is about 18' clearance right where the tunnel arch begins it is 11'6". A couple feet into the arch it is 14'+. To not clear the 11'6" you would need to almost be off the road. Other than that there is room for two rigs to pass in opposite directions in the tunnel. So...did the GPS do it's job? My vote No. Yes it should have gave a clearance warning but not a restriction and rerouting. Like has been said over and over double check your route. Don't trust the GPS as the final answer.