Does anyone know if fitting a bull bar or Roo bar to the front of a van improve it's frontal impact resistance or would it just make things worse?
It would depend on what your van is running into. If your van with a bullbar hit a cat or rabbit then it would probably help protect your van. If your van had a head on with a prime mover where both vehicles were doing 100 km/h then a bullbar wouldn't make much difference as you'd be dead either way.
I'm talking about adding protection in medium speed head-ons where the driver is very vulnerable.
There's a theory that the bar folds back comes through the sheet metal and chops you at the knees. A bit like the steel caps in safety shoes cutting your toes off. Probably both myths. Progressive crumple is what slows down the peak deceleration. Bullbars being mounted down below probably bend fairly easily until the chassis rails take up the strain. So probably not much.
What bullbars do do is make it much worse for pedestrians. A flat deformable panel is much better to collide with than a cheese grater..
I haven't seen many pedestrians carrying bull bars. I guess normally they don't travel fast enough to need them, not to mention being really heavy.
I have a bull bar on my van and it sucks.. It's anti-social, ugly, heavy, I feel like Mr Plow.
My van has a little bull bar on the front but it does not look very strong. From what I have read, after market bars usually are more likely to cause injury. However if you are driving a van that protects your feet with a thin sheet of metal then it probably doesn't make much difference. Your legs and feet will be crushed either way in a moderate front on collision. Your best bet if you are having a collision could be to pull up your legs if you get a chance.
I got rear ended by a Kenworth truck in march and rammed into a ute,I can thank my lucky stars that one it was a VW and two that I had a Bull bar.The van was written off and all I got was some scratches on my feet from the pedals.
I fitted a kn huge bullbar on my old hiace commuter when I was travelling into melbourne regularly.
Once I got the bar, everybody gave me room ,very few cars cutting off the slow old bus.
the only scratches it ever got were from pushing the occasional little firewood tree.
If I bought another van I wouldnt hesitate to put one on
One of the reasons I avoided a Toyota van, was because of the forward control position. The ride is horrible, and only made worse by having a big steel bull-bar adding stress to the shocks.
Adding a steel bull-bar should always include a suspension upgrade, or you adversely affect ride, handling, and braking, as well as shagging the existing suspension in no time.
I had a Hilux with one, that had turned the leaf springs upside down.
The Merc and VW vans are a much better ride, with the car-like position and some crumple space between you and an impact. The trade-off , of course is the loss of Japanese reliability in exchange for Euro-dodginess.
Maybe the Hyundai's really are the best option.
. I'd only recommend a bullbar if you do a lot of country driving and even then limiting driving around dawn and dusk times to reduce fauna strikes
. For city or suburban driving there really is no need to be equipping a van or any vehicle with that kind of protection.
Looks like bullbars are a bad idea. Maybe forward control vans too...
Might have to settle for euro style dodgy reliability...
There are all sorts of collisions. In a T bone collision the wheel and axle on an old style van probably acts as a better side intrusion bar than the one in the door of a ford laser. And your head might be above the top rung of that bullbar on the ubiquitous Hilux.
Any car with curtain airbags should be better still. Curtain airbags are a great invention, make sure your next car has them.
There are a few Japanese vans that have the motor up the front. The Hiace previous to the current model has a motor at the front. The Mitsubishi Delica and the Express with the same body has the motor up the front. The Nissan Elgrand has an engine infront of the driver instead of under the feet.
I had a Kombi with a bullbar (did lots of driving in the country), but apart frrom fending off roos, it's main function was to hang towels and wetties on to dry. Very usefull.
If you drive a van (and I did for about 15 years) you should be thinking about driving slow enough to (hopefully) avoid having to use the bullbar - chill out, cruise, and enjoy the scenery. Actually, do this whatever you drive!
I have a 2000 model Ford Ecovan (Mazda 2200??) that had a windscreen wiper motor problem which meant I had to remove the dash to fix it.
Ever since then I drive a lot more cautiously in it !! 
The only thing between your knees and whatever you hit up front is a flimsy front panel, a heap of wiring harness, a dash that is a mix of light steel and plastic crap - all mounted on a 50ish mm steel tube which attaches to the door pillar section with a couple of bolts each side.
The only thing a bull-bar would do in a front on is help push the whole front end and steering column into you knees and lower body..... ZERO crash rating I would think.
Next van for me is most likely an Iload. 
I put one on my hiace.
Rationale being that without one it's like having a coke can stick taped to each patella for protection.
I figured the most likely crash where I lived the time (wanky suburb called Brighton in Melbourne) was getting hit by a mum in a big 4wd at low speed while she was on her phone, sipping latte and talking to her kid in the back.
Bull bars would be enough to protect my knees in that situation so I got them
If you have a van and want a bull/roo bar do it, I did but mines a 4x4 van, spreads the load across the front. I've tested mine, a rear ender into a 4x4 trayback my fault and everyone had happy feet 
If a real 4x4 or truck etc tries to come through your door at speed you're in trouble if they have a bull bar or not, hell even a Commodore will ruin your day. 9 times out of 10 in a side impact what will get you is your own B pillar, as some one said side air bags are gold.
