In article , Phoenix
Pilot wrote:

I have always been under the impression that when you see those lines
you don't cross until your given permission too (cleared onto the
runway, etc.) However I'm currently working on my CFII right now, and
my flight instructor the other day told me that those areas are not
always active and you don't always have to hold short of them.

Your CFI is right. It's the controller's job to protect the critical
area if the weather is low enough (under 800 & 2) to warrant it. If
you need to remain clear of the critical area, the tower will instruct
you to do so. Absent any instruction to remain clear of the critical
area, you're expected to go all the way to the hold short line.

A quick search yielded, among other things, this document:

http://www.rduafss.faa.gov/navaids/ils.htm

Section K has the details on the critical area.

--
Garner R. Miller
ATP/CFII/MEI
Manchester, CT =USA=