[OSM-talk] How do bridges work?

[Rick Collins]

I spent some fair amount of time yesterday trying to get the highway 
bridges setup correctly (or what I thought was correctly) in my 
area.  Now I see that they are nearly all displayed wrong.

I see bridges displayed three ways.

1) Displayed as I intended with a roadway shown on top of the roadway below.

2) Displayed with the wrong road on top.

3) Displayed with the wrong road on top and the road that *should* be 
on top seems to be broken with rounded ends which may or may not show 
on top of the other roadway.

Yesterday when I was viewing this section, I could actually see lines 
drawn to indicate the ends of the bridges.  Now I see nothing like 
that and even the bridges that look ok can't be distinguished from 
intersections.

I used a "bridge" = "yes" tag on all of the sections that should be 
passing on top.  They were not displaying correctly so yesterday I 
added a "layer" = "+1" tag to each of them.  This looks worse now 
than it did before I changed it.

Am I still doing it wrong?  How do I get bridges to display correctly?

Also, there are a number of roads in the area that are being 
constructed.  I recall that it is not uncommon to put these streets 
on maps and label them as "planned" or "under construction".  Is that 
being done in OSM?

Likewise, is it useful to add ways for roads that I know exist, but 
that I don't have traces for?  Tiger data is being uploaded for the 
US and I see tags such as "Tiger:reviewed", most of which are 
"no".  Is there a similar tag for uploading your own data that has 
not been measured?