Editing a city map (how to thin streets)

I'm creating a community map for our town and I received a very large TIFF file and I've done some editing on it. The streets are rather bold and I want to know how I can thin them using photoshop.


Here is a link to the image. Don't worry about the street names; I'm going to edit those out and add my own. I just need to know after I take the street names out, how can I make the lines thinner.

http://www.silkscreenbiz.com/communitymap2.gif

BTW, I have PS 5
THANKS SO MUCH
Ryan

After you edit out the street names, copy and paste the map into a new alpha channel. Then hit Ctrl>I to invert the colors, Ctrl-click on the alpha channel, go back to the normal document, go to Select>Modify>Contract, and input the value you want to contract the lines by. Then create a new layer and fill the selection with black. That should do it.

Depending on the tif file you can possibly use >filter>other>maximum to thin the lines globally throughout the image in one swoop.

but if the minimum setting for that filter (1) is too drastic I would do what Mad said.

Thanks MAD68790, I tried what you said and it worked great.

THANKS FOR YOUR HELP

Once I'm done with the project I'll post it.


Once again thanks,
Ryan