On the eve of the busiest travel day of the year, AAA is predicting an overall drop in Thanksgiving travel.   The projected 1.2-percent dip in holiday trips would be the first decline since 2001 and 2002, the first post-9/11 Thanksgivings.

In recent weeks gas prices have fallen to less than half of what they were last summer.

But this year is also the first holiday we’ll celebrate in the grips of the financial meltdown, and the first in the wake of this summer’s $4-plus-a-gallon fuel prices.  It’ll be interesting to see who flies, who drives, and who stays close to home over the long weekend ahead.

It’s also a good time to take stock of The Year in Petroleum so far:

The gas-price spike really hit home in July, with about a three to five percent decline in vehicle miles traveled over the previous July.   The American Public Transit Association also reported that midsummer commuter bus and train trips jumped about 5 percent over last year.  (Althought the Los Angeles MTA and its commuter rail counterpart, Metrolink, just announced that ridership is back down by as much as 3 percent since mid-summer). 

The summer also saw two more correlated pieces of healthy news:

As prices rose in early ‘08, the National Safety Council noted a 9 percent drop in vehicle-related deaths (See, OPEC and the oil companies were just looking out for our safety!).

And the EPA reported that ground-level ozone levels (a.k.a. “smog”) fell this summer in all but two major metro areas in the U.S.  Ground-level ozone is a warm-weather pollution threat, caused mainly by tailpipe emissions reacting with heat to create smog.  Fewer tailpipes on the road = less smog.   (This one may also be due in large part to very active wind patterns through the summer, according to CNN Meteorologist Jacqui Jeras).

Here in the Southeast, we’ve seen perhaps some of the wildest price swings in gas:  The refinery shutdowns following Hurricanes Gustav and Ike caused widespread shortages in September, and prices shot up to $4.30 a gallon in my neighborhood.   Yesterday I saw one of the same stations selling the same gasoline for $1.62.  Which begs the question:  Did you change your driving habits this summer when prices went through the roof?   And are you changing back now?

I’ll start:  I’m finding it a little harder to drag myself to the bus stop and am driving more often.   What about you?

–Peter Dykstra, Executive Producer, CNN Science, Tech & Weather

When powering the green car of the future, one man is turning to Fred Flintstone for inspiration. Charles Greenwood is the creator of the HumanCar, an automobile that’s powered by you and me and maybe some of your friends.

The Imangine “Urban” concept design by Stephen Brand for the HumanCar.

Rowing handles produce the electricity the car needs to move it forward. Greenwood says it’s made entirely of recycled plastics and can reach speeds of up to 60 miles per hour as you row away, but he says there’s also a back-up electric motor in case you get tired of rowing.

“It’s just exactly like an engine firing around the four cylinder cycle. In this case, we can see we got one, two, three, four, firing around” Greenwood says as he points to four people rowing the HumanCar.

Greenwood’s son, Chuck, the CEO of the HumanCar design company, says one of the designs, the Imagine_PS Electric-Human Hybrid Car can also be a source of power for your home: “Theoretically, you can operate 100 of these vehicles to create a 100-kilowatt mobile power station.”

The HumanCar costs $15,500 and you can pre-order one for a $99 deposit. They are set to roll out next year on Earth Day.

What do you think? Is a human-powered vehicle a good fuel alternative? Wouldn’t it be easier and cheaper to just ride a bike?

Paulo Nogueira — Producer, CNN Science & Technology

Hard, flat, tough, solid. These are all words that you could use to describe concrete. But green? That’s not usually an adjective many people would apply to cement – unless, of course, they knocked over a can of emerald paint on their driveway… But here’s a rundown of some new environmentally friendly products that are paving the way to greener, well, pavement.

Workers lay Filtercrete (left) and Flexi-Pave (right) instead of regular concrete. Source: CNN/KBI

Filtercrete: Recently used to green Chicago’s alleys (watch story here), Filtercrete is one of a few products that help improve normal pavement by making it porous. It is filled with tiny holes that allow water and air to flow between the surface and the soil. This reduces the runoff to local waterways, while increasing water input to local underground aquifers. Because water is less likely to be trapped in the porous concrete, there is a reduction in cracks caused by water freezing to ice. Filtercrete’s holes also harbor bacteria that break down contaminants like oil and grease, so water is cleaned as it passes into the ground.

Flexi-Pave: KB Industries’ flagship product Flexi-Pave adds one more green aspect to porous pavement. Used for ‘low-speed’ surfaces like sidewalks, trails, and parking lots, Flexi-Pave is made primarily of recycled tires. Considering they are used at a rate of one per person per year, there are a lot of worn-out rubber tires out there that could be diverted from landfills and recycled into pavement.

Because it’s made of rubber, Filterpave can expand with any freezing water that happens to be caught in the product’s pores, further reducing the chance of cracking. Also, the product can be outfitted with subsurface heated water pipes to help melt snow lying on the pavement’s surface. “[It] causes any snow to immediately turn to water and pass through the product,” says Chief Operating Officer Trey Wylie, “[Clients] have eliminated snow removal costs and no longer have to apply chemicals throughout the winter.”

Air-Purifying Concrete: It’s still in the research stage, but scientists at the University of Twente in the Netherlands are developing a form of concrete that could help clear nitrogen oxides from the air. Nitrogen oxides are those chemicals that cause problems like smog and acid rain, but this new concrete will contain a chemical – titanium dioxide – that converts nitrogen oxides into harmless nitrate salts.

The salts are rinsed off the surface and into drainage systems when it rains, and the concrete should continue to perform over time. “[Titanium dioxide] is a catalyst, so it is enabling the reaction, but not participating, not consumed, so it never wears out,” says researcher Jos Brouwers. He adds that the air-purifying concrete could potentially be combined with porous concrete products like those mentioned above or even used in decorative facades of buildings. Results on how effectively the concrete performs in field tests are expected in 2009.

So what do you think of these products? Where can green pavement go from here?

Julia Griffin, CNN Science & Technology

Having grown up in a major southern city in Brazil in the late 70s and 80s, I can vividly remember going to any fuel station and the attendant asking my father if he wanted gasoline or “alcool” — ethanol made from sugarcane.

A worker cuts sugarcane at harvest. Source: Getty Images

When I moved to the U.S. in 1989, I realized that American drivers didn’t have the same choice as we did in Brazil, but gasoline here was so cheap and abundant that there was no need for an alternative.

Well, you don’t need me to tell you that times have changed. While politicians try to spread the blame and try to feed us ideas that will get them elected or re-elected, gas prices continue to go up.

Most Republicans in Congress want to drill in Alaska’s ANWR (Arctic National Wildlife Refuge) as a solution. It sounds sexy enough to say let’s drill on our own turf and flip the middle one toward the Middle East, but the reality is that it would take years for any of us to see a drop of that oil in our tanks and there isn’t enough there to suppress our addiction to it.

Speaker of the House Nancy Pelosi says the immediate solution is to open up our oil reserves, which we’ve already paid for as taxpayers, and make it available right now instead of drilling in ANWR. That sounds like a great idea, in theory. But if oil is our heroin, Pelosi is basically saying let’s make more of it available to all addicts so that their withdrawal is mitigated. How about when the reserve is gone? What are we going to do then?

I’m not suggesting we follow in the footsteps of Brazil and mass produce our own ethanol. We’re trying it with corn, which is driving the prices of food and basically everything way, way up. What works in Brazil may not work elsewhere. Besides, Brazil has its share of problems with ethanol — the Amazon rainforest continues to be cut down to grow more sugarcane. This year, 24 ethanol producers were fined in the millions for planting sugarcane illegally and operating without licenses, among other things.

We must look toward other solutions, be it hydrogen, electricity, solar power or even water. Whatever the answer, our children and grandchildren will either suffer or benefit from the decisions we make today.

What do you think is the answer to our oil addiction? Do Republicans and Democrats have a solution or are they sidestepping the real issues? And how are you coping with the high gas prices?

Paulo Nogueira — Producer, CNN Science & Technology

T. Boone Pickens talks energy on CNN in May

Pickens has an astounding track record at anticipating U.S. energy demand — including a prescient warning a few years back that oil was going to be mighty costly about now. Like the old E.F. Hutton ads, when he talks, investors listen. And if he says wind is in, investors will line up.

I’d love to hear your thoughts on his plan.
To start off, here’s my own two cents (bear in mind that I could be out buying one-third of an ounce of gasoline with those two cents):

1. Pickens is neither an altruist nor a treehugger trapped in the body of an oilman. He sees money in this, and has been perfectly transparent about that.
2. It’s a plan — at least a partial one — which is pretty much more than we’ve got now.
3. It may be a plan from a shrewd, battle-tested business tycoon, but it’s probably not as easy as it seems. Wind energy gives out when the wind stops blowing, and there’s no existing technology to store it in large quantity. Wind-dependent power plants would need a robust backup system. We’d also need a much better electric transmission infrastructure than we have right now, in order to move the wind power from the Great Plains, where it’s available, to the population centers, where it’s needed.
4. Wind as a main power source would have an uneven impact in replacing natural gas. About half of California’s electricity comes from natural gas. In Ohio, it’s about 2%.

Your turn — blog away: Is T. Boone Pickens a genius, or is he just spittin’ in the wind?

Peter Dykstra Executive Producer CNN Science, Tech & Weather

Yeah, another bad headline — doesn’t sound possible, you say?  You may be right.  But I just saved $350 outright because gas prices are so high.

Getty Images

A decade ago, we opted to move pretty far away from the center city:  27 miles from the driveway to CNN Center in Atlanta.  The decision was largely due to the prospects for our three school-age kids:  A shaky, in-town school district versus a well-regarded one farther away.  And since the State of Georgia always finishes in the Top 50 among State Educational Quality, we went for it.

The kids have had a good shake in their schools, so no regrets.  But the costs for Daddy driving to work have included up to two-hour commutes, plus more recently, brutal gasoline costs, even with a 32MPG car.

A few years ago, in a nod more to traffic burdens than to energy or environmental concerns, Georgia rolled out commuter buses to far-flung places like Conyers, GA.  Five per day, from the commuter lot next to the Rockdale County Jail into downtown Atlanta.  So yes, I go to the County Jail at least twice a week.

Being in the 24-hour news business, I feel obligated to give you the Bad News First:  The last bus in is at 8am; the last bus back is at 6:15pm.   This does not always fit the bipolar nature of covering 24-hour news.  Bottom Line:  I can’t always rely on the bus — not for late nights, or weekend work.  The Good News?  My employers have had the foresight to let me keep my parking privileges for when I have to drive, plus a part-time pass for the bus.

With minor inconvenience, I can take two bus trips a week to work, with little or no compromise to my workload,  saving 2 gallons of charitable donation to the oil companies per day, plus environmental benefits, per round trip.  But I called my insurer (GEICO), and they also told me that the reduced mileage on my car would save me about $350 a year on insurance costs.   Whoa!! Just think how much extra gasoline I can afford now!!!  I won’t have to take the damn bus!!! (Just kidding).

Actually, the bus isn’t bad.  It’s still only about half full each day, which is amazing to me.  I can listen to my IPod on the way in (it has a lot of songs on it, and you wouldn’t like most of them….), and I arrive at work bearing no anger to all the Barbarians and Fools who would tailgate me or cut me off on Interstate 20 on the way in (full disclosure:  It’s never my fault as a driver; to quote Dustin Hoffman, I’m an excellent driver.) .  Oh, and on the way in,  I read stuff, too.  One more note:  They’re considering Commuter Rail from many towns like Conyers, but ’round here, the feelings still run strongly about General Sherman tearing up the railroad tracks 144 years ago, so it may take a while longer for the State Legislature to warm up to the idea.

So I’d like to thank the Oil Companies, OPEC, the shrinking dollar, the increased international demand, the speculators, the guys who blow up the pipelines in Nigeria every week, and everyone else who’s been blamed for high oil prices for making my ride to work more relaxed and a tad cheaper, at least twice a week. 

Peter Dykstra    Executive Producer   CNN Science, Tech & Weather

It may sound backwards, but that is how two Duke professors suggest we gauge fuel economy.

MPG to GPM Conversion Chart

Richard Larrick and Jack Soll of Duke University’s Fuqua School of Business say the phrase ‘miles per gallon‘ misleads consumers.

The premise of their study, published recently in the journal Science, is that you save more gas by switching from a 10 to a 15 MPG car than by trading in your 25 MPG ride for, say, a 50 MPG Prius.

If you’re scratching your head, consider the following equation:

Driving a 10 MPG SUV for 100 miles requires 10 gallons of gas, while one that gets 15 MPG will burn 6.7 gallons of gas on the same trip. So the jump from 10 to 15 MPG is a savings of 3.3 gallons of gas.

On the other hand, the 25 and 50 MPG cars burn 4 and 2 gallons, respectively, on a 100-mile drive. That is a savings of only 2 gallons compared with the SUV driver’s 3.3 gallons. You see?

So when it comes to saving money, Larrick and Soll say it’s less about buying the most fuel-efficient car, and more about removing the most inefficient vehicles from the road. They recommend fuel efficiency be displayed as ‘gallons per 100 miles’ (GPM) instead of the traditional MPG.

That way, instead of aiming for a car with the highest MPG, consumers would be striving for the lowest GPM rating.

The point is to help consumers easily understand the amount of gasoline they will save when they trade in a car.

It’s simple math. To calculate gallons per 100 miles, simply divide 100 miles by the vehicle’s MPG rating. However, this calculation is not one consumers seem to do when considering a new car.

For example, Larrick and Soll asked participants in their study to decide whether replacing 15 MPG vehicles with 19 MPG ones was better or worse than exchanging 34 MPG vehicles for those with 44 MPG ratings.

Groups given the vehicles fuel efficiencies in MPG chose the wrong answer of 34 to 44 MPG 75% of the time. On the other hand, people given fuel efficiency choices in GPM made the wrong decision only 36% of the time.

So yes, it’s still true that driving vehicles with the highest fuel efficiency possible is still best for the environment, but as gas prices rise will consumers be making their trade decisions for Mother Nature or their wallets? If it’s the latter, they may need GPM instead of MPG to make the best choice.

Test your MPG understanding at: http://www.fuqua.duke.edu/news/mpg/mpg.html

– Julia Griffin, CNN Science & Technology