<div><span class="gmail_quote">On 9/20/07, <b class="gmail_sendername">Alex Mauer</b> <<a href="mailto:firstname.lastname@example.org">email@example.com</a>> wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
I don't consider subways to be "in a tunnel"</blockquote><div><br>Well, tell that to the tunnelling engineers!<br> </div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
I consider them to be<br>simply below (most) everything else. Besides that, the roads as you say<br>are on bridges; the subways aren't in tunnels.<br></blockquote></div><br>Alex, I'm not sure whether you've much knowledge of the London Underground network, so please forgive me if you knew any of this. However, it is necessary background for understanding the tagging system.
<br><br>The London Underground is a large electric standard-guage railway network that covers most of Greater London. There are on this network several different sections of track<br><br>*mainly in the outer suburbs, there are sections are at ground level, and look pretty much like any other commuter rail system
<br>*in a few places, there are sections which are elevated on embankments, well above ground level (ie layer 1), and here the Underground goes on bridges over various roads (bridge=1 for short sections)<br>*in a few places, there are sections in cuttings (ie layer -1), which nontheless can see the sky for large parts. A few roads will cross these on bridges. Here, we can have the road bridges be layer=0, bridge=yes
<br>*in a few places, there are sections in tunnels of various depths. these sections cannot see the sky, roads that happen to cross the path of the deep level tubes certainly aren't considered bridges. this could be represented as tunnel=yes, layer=-1
<br><br>The tube network is all interlinked and most lines use a combination of these different types of rail setting. We tag all of it railway=subway, whether or not it is actually underground or not, because it is all the same system.
<br><br>What you are suggesting would lose the subtlety of the distinctions, especially between subway in an uncovered cutting - which will be visible from roads - and subway in an actual tunnel. Now do you understand?<br>