Question:
No,,,it doesn't, most likely. And all that fiberglass that makes up that new home-away-from-home that you are so proud of is about as strong as,,,well, fiberglass. It ain't built to protect yur noggin' if you turn 'Ole Betsy on its side, or worse.
You wanna find out what happens to Billy Big Rigger when he screws up and has a wreck because of following too close, too fast down the BigHill, runnin' tired, etc, etc, etc., then go here and look at some photos from this site.
Quit following too close. Quit following too close. Quit following too close.
http://www.truckcrash.com/truck01.htm
I want a cage like the Big Boys in Nascar
Politicians Prefer Unarmed Peasants.

Answer:
in most cases trucks don't need roll bars/cages. The frame is strong enough and in newer trucks the windshield is an integral part of the support system, which is why it is important to repair any cracks or dings in windshield. I have seen trucks on the roof with only a crunched sleeper. But good message.
STAY BACK!
If at first you don't suceed, get a bigger hammer

Answer:
You're following Too Close for Comfort.
BE SAFE & HAPPY TRUCKING
SMYLE!

Answer:
Ed, if you REALLY want a roll bar in a truck then you are stuck with the VN line of Volvos.
Having tested this myself, I speak from experience. The Swedish gov. requirements for roll over construction are TWICE what the US regs are. Same with all collision impact requirements.
But then the Swedes have always required the most stringent safety requirements.
Found this out AFTER I pole vaulted my 98 VN-610 onto its roof by getting a spread axle flatbed sideways in a 7'ditch. The back of the flatbed dug into the soft soil and actually acted as a pole and flipped the tracor about 40' in the air. To land directly on the top of the cab. I walked away.
In my Classic, any paccar product or other make I would have been compressed into my seat or lower.
They may be ugly to some, but the Volvo VNs ARE the safest trucks on the road.

Answer:
Thanks Polevaulter, (whoops, I mean Skiffman!) Sounds like that was a heck of a ride; glad you walked away. I once drove a 610, tho my first company had half the fleet repo'd by Volvo and got laid-off. ha.
I'm going with a company next week that has condo Volvo's; 710's ? i think. Anyway, I KNOW Volvo's are safest, from what I've learned. Got a really nice ride too. Heck of a lot better than International Eagle. yuck!
If I was O/O, I'd probably make some sort of 700lb. or so roll bar outta oilfield pipe right behind the driver seat, going up a foot or so above me noggin' Who cares about weight!!!??
That truckcrash.com site has lots of cool insights that folks just starting out will probably enjoy learning/reading. The 'editorial' links have some good articles. The guy is really into [SAFETY/], which is the real reason I posted his link in the first place. I've learned a lot from TruckNet, too, and all the great posts from all you drivers out there. I'm just tryin' to 'give back' a little bit. Hope it helps.
Common sense and anticipatin' 'what ifs' along the way, are the best way of keeping out of trouble w/4-wheelers. If you THINK they might be about to do something StOoPid, they PROBABLY are, and as 'Professionals', we're supposed to help 'em out and not run over 'em, is my outlook on it. Better to slow down and lose a few seconds than to waste a half-day or more in a wreck. Might just save yourself or them a trip to the Big Eternity.

Answer:
This happened at 57 mph in the middle of a 5 mile straightaway, clear day, no traffic in either direction. I checked for on coming traffic, looked for something I wanted to grab, looked back to the road, reached for it while looking ahead. Then glanced over to see if my hand was close.
When I looked back I had drifted to the fog line. when I corrected the trailers back axle dropped into the freshly turned shoulder. After trying to get it back on for about a mile, the level shoulder turned into athe 7' slope. It too was very soft( the area was recently cut back to keep from icing. the back axle sunk in more pulling the front in too. By now I'm slowed to roughly 25 and was going to come to a complete stop to use boards to "ramp" the back axle onto the road.
Never got the chance as the whole trailer caved the bank( 49,000lbs of glass with 39K on back axles. Spread with a scale) and went into vault mode
Thats why they are called accidents.
Sure glad I wasnt doing 70mph!!!!

Answer:
wouldn't say no to a VNL770. Black or Torreador Red. The new 780's are a bit funky lookin but I'll bet that thing just slips through the air.
It's like "cleaning up" an airplane. The more aerodynamic it is and the less drag it produces the better your fuel burn will be.