Other studies like this have been done here
http://www.greencarcongress.com/2006/11/study_improveme.html
and companies like WalMart have been using these for years
http://www.greencarcongress.com/2005/12/walmart_seeks_t.html
and you know that if WalMart is doing it, it's for the bottom line (and not for environmental reasons).

So why isn't everyone getting getting a truck skirt? Especially those independent truckers that went on a silly strike a few weeks ago to protest diesel prices.

Here's a company that sells them
http://www.freightwing.com/index.html

I wonder how much these things cost?

it seems to me that the biggest component of drag is the square tail. has anyone looked at the various components of drag (nose, wetted area, tail etc)?

It seems that maybee a decade ago in Europe there was interest in installing inflatable spoilers on the end of trailers. It wouldn't help the first truck on fuel use but it would reduce the fuel consumption on the trucks following close. There must have been a GPS-device regulating the rear trucks engine speed for safety reasons. The main reason at the time was to be able to cram more trucks in the lane.

sjc, you said:

"So why isn't everyone getting getting a truck skirt? Especially those independent truckers that went on a silly strike a few weeks ago to protest diesel prices."

Waitaminute. I don't think anyone has thought about fuel efficiency with a truck much less a heavy duty or an 18 wheeler. I get the feeling that truck companies should be considering testing their trucks in a wind tunnel to improve fuel efficiency.

One can also place partition pieces out in front of the nose of a truck and create a more streamlined shape.

Gerald,

You attributed Karkus' quote to me. I saw a video of a pickup truck that hit the side of a jack knifed trailer and sheared the top of the pickup cab right off. It is a safety issue as well as a fuel savings and by extension, national security issue to get more mileage out of truck travel.

I would guess the reason that independent truckers have not done something like this is cost. They are paying for their rigs and fuel, they do not want to pay for this. Maybe the government and tax payers could help. It is good to save fuel for lots of reasons and when you combine safety, it is in the public interest to do so.

The fuel saving idea is not really new.
Side skirts help, but so will underskirts, as will either boat-tails or some other rear square-reducing method to improve airflow.

However, often trailers are owned by the transport company, while the truck is owned by the independent trucker.

It would be nice to see side-skirt and under-skirt kits made available for all standard sized trailers, with perhaps a tax incentive or grant program to have them installed, and perhaps extra charges at tolls for trucks without them.

I am seeing and expect to see more good ideas being used by the large in house over road truck operators such as Wal-Mart. They probably control both the truck and the trailer.

I would be interested in seeing a trade off between this type of add on and the reduction in speed in 5 mph increments. My guess is you could get some very quick results close to these just by changing driving habits.

Frontal configurations have the most effect on aerodynamic drag as compared to rear aerodynamics. Frontal streamlining & rear boattails make the truck-trailer combination longer which are already at the maximum legal length. One method from 1960's station wagons would be an aluminum fixed curved spoiler at the top rear of the trailer(& spoilers along the verticle rear edge if possible) which would skim boundary layer air & force it to fill the vacuum behind the trailer. These devices would often be subject to damage.

Making the sideskirt bottom strong enough to carry extra cargo would make placing cargo down between the wheels difficult & would require extra power equipment other than folklifts. Special strapping so forklifts could lower cargo between the wheels would really reduce a cargo area already pretty small.

I beliefe most truck drivers are just contractors or employed staff here in europe. The percentage of truckers
owning the rig is probably less than double-digit.

Even at european diesel prices (currently at around 7,70 USD/gal) most trucks are speeding (typically, the speed limiter is set by default to the legal speed limit + 10 kph; however, a lot of trucks are going even faster, and this not only downhill...).

Obviously, the gain from being on time at all cost is larger than the cost of fuel - still. It seems to happen
a lot that if a driver is caught speeding with and has to hand over his driving licence, he is immediatily fired and replaced by another driver... Staff cost is
probably low too, as these companies employ mostly eastern europe citizens (low wages there).

Not really a job I'd like to have.

Anyway, obviously fuel at nearly 8 USD/gal is still way
too cheap to really think about transportation and
logistics in a grander scheme (ie. using rail instead of
road for distances > 200km; currently, long distance truck traffic is growing rapidely with typical routes around 1500 km.

Unfortunately, the oil price is not fundamentally high,
but the USD is weak; I'd think with USD and EUR were
still around parity, and Oil being that high then,
this would really make people reconsider (that'd be around 12 USD/gal for diesel).

Any bets when this mark will be exceeed?

One idea I thought of and have heard about are cruise control range sensors. They estimate that many rear end collisions and pile ups on the highways could be eliminated if the range distance between the car in front and the car in back could be computer monitored.

Not only would it prevent accidents, but a highway train of sorts would reduce drag and fuel consumption. People in Southern California routinely travel at 70+ mph with 3-4 car length gaps between them and the car in front. You might think you were on a race track.

This is not a good driving habit, because reaction time is 1/2 second at best and you are in the guy's trunk in a blink. You hear about these accidents everyday and I am amazed that there are not more of them.

With the range sensor computer, you could run at that speed and distance with a safety margin at the same time. Now on the freeways, if you allow 7-8 car lengths, somebody will just change lanes into that space. If we can save fuel and save lives at the same time, that might be a winning combination.