The regulation is pretty simple. It's just a matter of determining if the area is active (hot) and who is in control.
I found this while looking for information on Restricted airspace.
http://www.faa.gov/pilots/safety/notams_tfr/media/tfrweb.pdf
I flew by R-6901A and could not remember the procedures for going through it. I think it is get permission first. But still not sure.
Dan
§ 73.13 Restrictions.
No person may operate an aircraft within a restricted area between the designated altitudes and during the time of designation, unless he has the advance permission of
(a) The using agency described in §73.15; or
(b) The controlling agency described in §73.17.
The R-6901A notation states it is in operation on these dates and times:
May 1st through September 30th, 0800-2200 Local; and,
October 1st through April 30th, Friday 0800 to Sunday 2200 Local.
Other times are indicated by NOTAM 24 hours in advance.
It's area is from the surface to 20,000 MSL.
The controlling agency is Minneapolis Center on 128.6 VHF and 363.0 UHF.
R-6901B, to the south is hot only by NOTAM 24 hours in advance.
Simply put, you cannot enter without permission of the controlling agency (Center) during the hot hours. Those hours are published on the chart with others indicated by NOTAM.
I would never count on a NOTAM becoming issued and making it into the system nor on time. If you're under VFR flight following, ask Center early on for permission to transition, even if it is outside the published hours the area is "hot." If you're under IFR, you're likely going to get taken around it even if the area were cold. That doesn't mean you can't ask if its cold and request transition. The controller may or may not authorize entry.
If you were from the northeast and landing at Sparta, they may take you around to the south or may send you straight through the restricted areas. It's six of one and half dozen of the other depending on what you and the controller work out. But, you have to ask for what is more beneficial to your flight and its safety.
If you're simply flying past the area without flight following and not asking center, it's better to just remain clear. If you don't have GPS, make use of VOR radials and/or airways to remain clear.
The next more critical is Prohibited Areas. Those get you free military fighter escort and maybe some free coffee upon arrival during the several hours of questioning to follow. Never enter a prohibited area. I understand Camp David (P-40) still sees a few hundred incursions a year. That's a lot of coffee the government may be paying for!
I'm not gonna get into ADIZ and DCA. It's enough to make me remain in the South for life. TFRs are a no-brainer. Those will get you the above and possibly national attention on the nightly news. Wanna be famous?
Luckily, it's easily visible from the air, as there are fields around it and then the R-space is a bunch of trees. Every so often, they just go in there and bomb the **** out of those trees! 