What is correct method for portraying a divided highway that merges?

I am very new to all of this. I noticed that while using routable OSM on my Garmin, that the Garmin provided incorrect turn by turn directions because a divided road merged to a non-divided road and it was not depicted properly. Naturally, in the spirit of open source and community, I thought I’d just log in and fix the problem. However, as it turns out, I’m not sure I know how to do it properly. Can someone please provide me some guidance on this issue?

The location is here:

Notice that Jones road is divided on the west side of Highway 249. The map shows it changing over to a single road at the southwestern service road providing a little “jog” that is not really there. Notice also that Jones Road becomes Lake Road at the northeastern service road. This is correct. However, the underpass beneath Highway 249 is divided as well and is still Jones road.

If I had to guess, I’d probably depict 2 ways both called Jones Road extending from each side of the divided portion of Jones and merging into the single way that is Lake Road.

Any direction would be appreciated.


Hi Charles. You’ve picked a tricky spot to begin learning about editing the map, but it’s a fairly typical kind of mess we need to sort out in the TIGER data. I’ve fixed this one junction myself as an example. Here’s what I did:

  • I deleted a lot of nodes which were unnecessary. (When a road is completely straight you only need two nodes at either end to represent that)
  • The Jones road section underneath the main highway was joined onto the highway. I selected the shared node, and press minus (-) to untangle this.
  • I merged that section into one of the two oneway=yes ways, and extended the other alongside it to make the road going underneath the highway into two carriageways
  • I created a Y shaped junction where Lake Road meets the highway to connect things together topologically.
  • Arrange this part of the highway to line up with aerial imagery
  • I split the highway twice to create a short section tagged bridge=yes, layer=1
  • I added oneway=yes to all the roads apart from the two-way Lake Road

Take a look at what I did. Hopefully that makes sense. Now feel free to go find another junction to fix up! You won’t have to look far (e.g. the next one to the north of there!)

Thanks Harry!

On the one hand, this is a bit daunting – because I want to edit things correctly. On the other hand, some of this stuff is so messed up, it seems that anything I do in good faith has got to be an improvement.

Yes, the TIGER-Data needs a lot of cleanup. I went to Kansas City a few weeks ago. After I downloaded the maps for my Garmin I was so disapointed that every route I tried ended underneath a bridge and continued on top (or vice versa). So I tried to clean up highway connections before my departure date… We used a TomTom from the car rental company when we were there. :frowning:
Everytime when I have nothing else to do, I check highways and motorways and remove connections and add bridges and tunnels according to Yahoo where necessary.

Several other users and I have spent a lot of time fixing up Interstate Tiger data. I believe all interstates are fully routable in SC. One of these days, I’ll have to figure out how to load that into my Garmin and check out the turn by turn routing now!

I took the Worldwide routable Garmin map from Lambertus.

Thanks, that is a fantastic application! I’m currently squarely under a red tile, probably caused by the fact that most of the area under that red tile has NHD data recently uploaded. Eventually the data will be reorganized, so I’ll check back on the map periodically to see when I change from a “red state” to a “blue state”. :slight_smile:

The NHD data is definitely a requirement, but I hope that I'm not making the map more unwieldy due uploading the huge volume of water body data.   It definitely complicates playing around with the data on your home machine and creating great applications like the packaged Garmin maps.