I generally don't worry about clearance, as it's usually pretty easy to see what is or isn't in the way. It might, however, be useful if I wanted to "pole" a car to a different location.I do use markers, though not for clearance, but simply to indicate where magnetic uncoupling can take place.
I originally used Kadee in-track magnets for staging areas, and the Rix magnetic "wand" for uncoupling pretty-well anywhere else.
When I added the partial upper level to my layout, the areas underneath became a lot less accessible due to limited clearance amongst scenery and structures.
I did an experimental test by planting small rare-earth magnets in drilled holes under the ties, and found them to work well. When I get some free time, I'll add the same feature, where possible, on the area below the upper level, and on both the main portion of the lower level (all quite easily accessed.)I did add one Kadee under-track magnet on a siding on the partial uper level, and it works well, but I'll be using the rare earth magnets pretty well anywhere else that can be easily reached, as the labour is pretty easy...scrape-out the ballast between three ties, then cut and remove that material which holds the ties together. It's then an easy operation to drill two shallow holes, drop the two magnets into place, then slide the ties back to their original spacing, and then install some fresh ballast.
All of the magnets used for uncoupling on my layout have (or will have, once installed) a yellow post indicating the location for uncoupling. These are easy to see both on the lower level and on the upper level, too, and, of course, on the single level, too.The posts are simple lengths of Evergreen .100" styrene rod, inserted into drilled holes. The stripe(s) make the post more visible, and multiple stripes indicate that there are similar uncouplers at the same point on adjacent tracks.
Here's a few in the staging areas, with Kadee in-track magnets...
...this one, at GERN Industries, is the only on-layout magnet that's visible...
...while this one is a Kadee under-track magnet, added in a depression cut into the plywood of the partial upper level...
...the track closest to the structure has the magnet, while the next closest track is the mainline to- and from-staging, on the opposite side of the aisleway. The track in the foreground is an elevated deadend, slated for cinder disposal, when I get around to building the loader. The coaling tower is out-of-view to the left.
This one is the experiment with the rare earth magnets...
...and the off-set of the coupler shows the power of the undertrack rare earth magnets, which are 8mm. in diameter and 3mm. thick.
Wayne
CN paints the sides of the rails bright green for fouling point markers. They are usually about half a car length past the physical fouling point.
If there isn't a mark or it's buried under snow (not that this ever happens in Canada) we still used the old fashioned arm test to tell if something is clear.
Greetings from Alberta
-an Articulate Malcontent
Yes, well on previous layout of LION I scratch built some yard lights to mark the magnets. After all, your little brakeman does need to be able to see watt he is doing...
The Route of the Broadway Lion The Largest Subway Layout in North Dakota.
Here there be cats. LIONS with CAMERAS
Interesting. Maybe I'll do that to indicate where my uncouplers are located. Thanks for the idea!
Simon
If I had known clearance markers would make for an article in MR, I would have done it years ago. Except unlike James McNab, I don't use plastic styrene strips attached to the ties. Like the prototype I have seen in my area, I paint the ties directly. Yellow inside and out and along the edges of the rails, inside and out. Thats before weathering and ballasting. Once that is done, they blend right in.