Navigation of a very tight course

Turn Guidance can be a trap on course crossovers if you unintentionally take a wrong turn onto another valid section of the course as it will continue to guide you along the new section.

You may find it better to switch off TG and rely on course points only, but be aware that they may not pop up until after you’ve passed the course point due to map errors and processing delays. The work around with courses created in Connect is to manually add Generic Points named TL TR etc, say 50m before a turn where necessary. Also, keep the map screen on for very tight courses

That sort of thing is likely asking too much for such a slow computer. 

These devices are try to figure out if you left the course to pick it up somewhere else. 

They can get confused if the course crosses over itself or goes over the same roads multiple times. Usually, they sort themselves out (the newer units are better at it).

It seems you what you are doing is going to cause the device to be confused very often and not allow it to sort itself out. 

Seems like it’s going to be a perpetual headache.

Yep.  I experience similar in trying to use Navigation in dense mtb trail networks for the reasons already mentioned by PeterK_55 and dpawlyk.  This has always been a problem with previous Edge units and so far the 840 seems similar, if maybe somewhat better.  What I do is create and download a course and just have it displayed on the map rather than have the device Navigate it and simply following the line on the map.  I don't think would work for what you are doing.  Perhaps one approach would be to create several simplified overlying courses to cover an area, one course would cover some of the roads, the other course the remaining roads, and after both have been ridden you would have covered all of the roads. IDK.  Just a thought...

I'm still doing these "tight" courses, and still experiencing strange behaviors.  The cities in Los Angeles and Orange counties (California) have lots of cul-de-sacs.  I carefully plot my course to ride to the end of each of these streets, but while riding, the Edge 1040 often does not send me onto these streets.  I think that when it fails, the street is less than some distance determined by the Edge.  (It might be 150 to 200 meters.)

Reading a thread about long routes, people made a distinction between the route as built with Garmin Connect, or Komoot, or other tools, and the route presented on the Edge 1040 after it loads the course.  I use Turn Guidance.  Some posts have said this may be the choice that causes discrepancies between the course as built and the course as presented on the Edge.  But following the course without Turn Guidance seems just as likely to get me off course, with so many turns and U-turns on my courses.

Can someone further clarify the difference between riding a course with and without Turn Guidance?

With turn guidance (the big white arrows), the device "walks" the loaded track/course and picks the roads/paths the track appears to follow. The turn-guidance is a second route/track.

Note that it doesn't matter what course creator you use. Though, you probably want to use Openstreetmap maps when creating the course (your device has Openstreetmap maps).

The devices have issues following "out and back" sections (where you use the same road/path in opposite directions). The issue seems that loses track (maybe, more so if you stop) and picks the wrong leg of the trip. This is related to the devices being able to pick on a track in the middle.

When creating tracks, the track is typically centered in the road. I suspect there would be fewer issues if the track followed the right side of the road (where you are riding). This would put a gap between the track sections going in opposite directions.

Following the right side of the road might kill a lot of British riders, but I understand what you're saying.

I have also noticed that where I want to U-turn at an intersection as opposed to at the end of a street, the Edge tells me to do a U-turn, then quickly tells me I'm off course, then recovers.  It's irritating, but I'm pretty used to it by now.

I also started using spoken directions recently, and have gotten some interesting output.  The Garmin displays "N Oxford Dr", and says "N Oxford d r".  It knows that "Ave" is avenue, and that "Rd" is road, but it says the letters for "Dr" and "Ln".  I haven't gotten spoken directions for a "Cir"  or a "Blvd" yet.  Certain seemingly easy words like "Hillgate" get mangled (Hillgut is what seems to come out).  And I have lots of Spanish location names in So Cal, which Garmin speaks correctly only part of the time.

colin-campbell said:

Following the right side of the road might kill a lot of British riders, but I understand what you're saying.

Heh. (They just have to run the route in the opposite way.) The key idea is to have a separation.

colin-campbell said:

I have also noticed that where I want to U-turn at an intersection as opposed to at the end of a street, the Edge tells me to do a U-turn, then quickly tells me I'm off course, then recovers.  It's irritating, but I'm pretty used to it by now.

Yeah. The kind of route you are doing doesn't seem very common.

I tend to keep an eye on the map.

dpawlyk said:

I tend to keep an eye on the map

I know it is a popular sport here to criticise Garmin navigation but as a rider that does lots of kms and has used Garmins for 10 years IMO the navigation software on the 1040 is much worse than previous especially with Turn Guidance but also without as about a third of my rides seem to be a very confused hybrid, (see threads about ghost courses and wrong navigation instructions), trying to follow the map is sometime the only thing that works, I now take my 530 with the same course loaded on all my longer rides “in case”. Garmin had better address this quickly as it has  become worse with each release.

looigi said:

Perhaps one approach would be to create several simplified overlying courses to cover an area, one course would cover some of the roads, the other course the remaining roads, and after both have been ridden you would have covered all of the roads. IDK.  Just a thought...

Yeah, I agree - for a 'burbing challenge like this, break it down into smaller routes to avoid too many repeated crossings, double backs, etc.