something else to think about. They show those tests as the car is -not- braking. Add in the nose down/ass up of a panic stop.. it can only get worse.
I can only say this about stopping. While I never drove a semi, I did a 10 wheeled box truck (took 2 counties to turn it around) and on a lark on an empty country road while empty, I took it to 50 and locked them up. The Skid marks were a little more than the length of the truck
ProDarwin wrote: I think its interesting most people jump to the argument that a semi should never outbrake a car anyway. I'm betting a lot of deaths are from people hitting semi-trailers that are parked on the shoulder, pull out in front, etc. You know, situations where the semi's braking capacity isn't a factor. Yes, in most situations, its the driver of the car at fault. I look at it like the increase in safety is huge for a very minimal increase in manufacturing cost and/or regulation.
Yes, I'd say at least 99% of these accidents are due to error by the car driver, either not paying attention or driving too fast for conditions. I also agree about many of these hits happen when the car is braking and slowing down, but the driver just didn't react in time.
I guess truck bumper height enforcement varies. The shop I go to will let some stuff slide, but the bumper height wasn't one of them. Lifted trucks aren't as common around here as they used to be, but the ones I see do have dropped rear bumpers and some sort of "addition" to the front. When I had a lifted '78 F150, I remember feeling lucky when the bumpers "just" eeked under the limit after I installed the 6" lift and 36" Super Swampers.
There's no way to design/build a 100% effective rear guard for a trailer, as pointed out in the story of the Italian accident. It's possible to design a car which can protect its occupants in a high speed crash (see NA$CAR, WRC etc) but no one wants to put up with such inconveniences in their daily drivers so we get milquetoast designs and a gazillion airbags to supply the illusion of safety. That means once over ~45 mph it becomes academic as to what someone is driving and what they hit, their survival is a matter of luck at that point.
The unsafe issue is not that semis can out-brake a car. They can't. Ever.
The unsafe issue, especially for hypermilers, is the reduced reaction time.
At 100' following distance, they've got about 1.2 seconds to respond. At 20', it is MUCH less. Since they can't see the road ahead, they will not be responding to foreseen road conditions, they will be responding to the truck's brake lights, or the visual impression of the rapidly approaching rear bumper.
Hope they don't have an additional distraction like a cell phone. 
A car can stop quicker, but not if they don't see what is coming.
Look at it this way... sure you can stop quicker. Can you do it blind folded? In 1.2 seconds? Is it worth trying?
National Safety Council says rear end collisions are the most common type of accident- over 2.5 million per year. 5000 fatalities annually. I have no idea how many involve trucks, but the one thing I do know is that they were ALL following too closely, and thought they could stop in time.
irish44j wrote:novaderrik wrote:That's exactly why. My office overlooks the loading docks and the truckers are constantly bumping it while backing.Ian F wrote: Some states (PA) have laws regulating the minimum bumper height for lifted trucks. In PA, it's 30" to pass inspection. I've seen first hand what can happen when a car goes under a trailer at speed. It was about 8 years ago on Rt 1 in New Brunswick NJ. A truck was parked on the shoulder and a 4-dr Cadillac had buried itself up to the rear window under the trailer. I saw the accident before a majority of help had arrived to block the view (during the lengthy recovery process, they put up tarps to block the scene from passing traffic) - it was obvious the driver was killed on impact. Unfortunately, no one will ever know why he was driving so fast down the shoulder and why he didn't see the truck. Since trailers don't have things like center brake lights to catch attention of the average appliance user, a semi-attentive driver might not notice a braking or stopped truck until it's too late for them to stop in time. While improving the trailer guards won't prevent every submarine incident (like the one I mentioned), it could help survivability during those "oh crap!" situations where a split second is the difference between stopping in time and contact.i drive a 120 mile stretch of I94 on a pretty regular basis, and i've always kind of wondered why they don't mandate a center brake/taillight in the rear of the trailer... some of those guys put a zillion lights on their rigs, but they never put a couple of them down low in the middle of the back of the trailer right at eye level for those of us that are driving passenger cars on their roads for some reason. sometimes there is reflective tape there, but reflective tape only works at night and doesn't light up when the driver hits the brakes. maybe the lights would just get broken out on loading docks??
in my head, i'm wondering why the lights couldn't be recessed in so that they aren't the thing that hits first, and why making the lenses out of polycarbonate and maybe putting them behind a steel mesh grill wouldn't protect them? hell, they are making bright LED light strips these days that you can hit with a hammer and they still work...
some of the independent owner/operators that have their own trailers have at least 100 lights mounted on each side of the trailer (one from each truck stop they stop at???) to make sure that every satellite in orbit can see them thru a thunderstorm, but they can't be bothered to put a few lights on the back of the trailer that are wired into the taillights that are already there to let people behind them know that they are hitting their brakes??
but i'm just a high school dropout, so my thoughts don't mean anything...
novaderrik wrote: in my head, i'm wondering why the lights couldn't be recessed in so that they aren't the thing that hits first, and why making the lenses out of polycarbonate and maybe putting them behind a steel mesh grill wouldn't protect them? hell, they are making bright LED light strips these days that you can hit with a hammer and they still work... some of the independent owner/operators that have their own trailers have at least 100 lights mounted on each side of the trailer (one from each truck stop they stop at???) to make sure that every satellite in orbit can see them thru a thunderstorm, but they can't be bothered to put a few lights on the back of the trailer that are wired into the taillights that are already there to let people behind them know that they are hitting their brakes?? but i'm just a high school dropout, so my thoughts don't mean anything...
You need to hang around a loading dock for a bit. Not only do they back those trailers into dark holes, but they do not stop until they hit something. As such, the docks have lots of heavy rubber cushions to spread out the blow. Some of them can and will impact lenses.
Personally, when I gave up driving commercial, I was considering how to add more tail/stop lights. It could have been done, but would have required reworking the entire rear end of my truck to accomodate them
edit Interesting article on stopping a truck
Look in the hotlink thread there are pics of 2 different Vettes that have rear ended a semi. In one the driver & passenger were obviously dead.
In the other the driver was pinned.
Driving behind or hitting it while it is stopped it doesn't matter, if something can be done to minimize the damage to the cars then it should be done.
I love the rear center light. It doesn't have to be located in the bumper, it can be mounted underneath the bumper and out of reach of the loading docks.
My big take home from this is that the comparison of the two trailers showed how to do gussets right, and why a little sliver at an angle that is nearly parallel to the tube is a useless waste of time.
The tiny wedge gusset on the bottom trailer was near vertical. It "supported" more of the vertical tube (i.e. extended further down the length) but did nothing to help. In the top video, the gusset extends down to a lesser degree, but forward a HUGE distance. They knew that impact would come from the rear, so they extended it even further forward than normal (i.e. past what would cause a 45 degree gusset)....it worked, and the vertical tube was unable to fully buckle.
The main reason you shouldn't tailgate a semi is blowouts or kicking up debris. A semi tire going at highway speed.
That's actually the reason why i try not to sit BESIDE the wheels of a semi. Ive had some go off while my car was more or less next to them and it's terrifying. Perhaps almost as dangerous because of the reaction it may cause, as from actual tire shrapnel.
I think its interesting most people jump to the argument that a semi should never outbrake a car anyway. I'm betting a lot of deaths are from people hitting semi-trailers that are parked on the shoulder, pull out in front, etc. You know, situations where the semi's braking capacity isn't a factor.
I agree with you. I think the stopping power of semis is a total non-issue here. but....
The unsafe issue is not that semis can out-brake a car. They can't. Ever. The unsafe issue, especially for hypermilers, is the reduced reaction time.
THAT is the real issue.
But i think most people are talking about what they dont know about as far as drafting. I've done some experimentation with my Insight on drafting, which has a very intuitive instant-mpg gauge which makes it obvious when drafting is working and when it isn't. What ive found is that in order to get the majority of the benefit from drafting, you actually only need to the front half of your car into the area where the trailer's 'wake' reconverges. Basically, there is a V of air behind the trailer. You just have to get the front of your car just inside the point of the V. You dont have to have the whole car inside the V.
I've found this spot is actually a pretty safe distance behind a semi at highway speeds. I think most people can figure out where this spot is because it's the spot behind a semi where your car is buffeted side-to-side. I think this too-close following distance that people associate with drafting is due to people just taking other people's advice on the internet and not thinking critically and doing their own testing. You dont HAVE to be an unsafe distance from a trailer to get an mpg benefit.
From my observations more drivers than not fail to keep a safe following distance even behind a box or semi truck where you are more or less blind to the road ahead. Too much preventable E36 M3 happens. BTW, speed limits are the law not a suggestion. All too often it seems like a free for all out there on the roads. E36 M3 like this is why I hate driving anymore.
I could rant on. 
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