one point being, if most of your driving is spent at 80 mph (i've heard this is the case for most commuters in the Atlanta area. very little congestion, but very long commute times at high speeds), then there is no economic or ghg-based reason to choose a prius over any other similarly aerodynamic car.

if your driving is primarily at low speeds, a prius will greatly improve your fuel economy over vehicles in the same size range.

the other point being, decreasing your speed from 80mph to 50 mph will, on average increase fuel economy by 20-70% (more for SUVs and trucks, I would imagine), unless you drive an overpowered and aerodynamic car like the mercedes c180k. this is why the US had a nationwide 55 mph speed limit that was put in place in the '70s. and why some countries (japan, new zealand) still have such universal limits.

i don't personally want a return of the 55 mph limit, but i understand how it would be helpful. it could possibly be a more effective way to reduce our imports of foreign oil than all of the corn ethanol legislation so far and it would certainly do more for our oil importation than drilling in the ANWR would. it'd also be terribly unpopular and further encourage people to buy SUVs and trucks.

As I recall, most drivers ignored the 55 mph speed limit.

Most of the in and out expressways at Atlanta are marked at 65. If you are smart, you will keep up with the traffic flow at 80 mph. If you don't, you will constantly get cut off and sooner or later, someone will hit you.

Under these conditions, it's impossibe for the Police to do anything. They don't even try. In fact, if they are dumb enough to get on the expressway for anything other than an accident response, they cause trouble.

I had a friend who commuted back and forth to downtown Atlanta for five years. After they let him out of the mental hospital he found another job out of town.

Here we go again. Comparing diesel and gasoline. For the xth time: diesel IS NOT gasoline, gasoline IS NOT diesel.

One litre of diesel contains more energy, costs more oil to produce and produces more CO2. So when you have a gasoline and diesel car with the same mileage, the gasoline car is about 12% more efficient (from a technical perspective) or 12% less polluting (from a greenhouse perspective). From the economical perspective things are different, but this site is called GREEN car congress :-).

Second detail that should be taken into account is the transmission. Were this cars with manual or automatic transmissions? I could not make this up from the article, but since this was a European magazine, I suspect all cars were manuals (except for the Prius of course). An automatic gearbox adds about 10% to fuel consumption.

Never trust facts until you've got them all.

Typo: average speed was 110-130 km/h

on a 300 mile round trip last weekend, all freeway, my prius averaged exactly 49.1 mpg with the cruise control set at 70. how on earth were these people able to get mid 30's !?!?!?

it would be interesting to do a full economic analysis of the cost of speed. For example, by driving faster, you spend less time on the road and more time doing something else you may consider more valuable. For example, if your time is worth $60 per hour either in terms of billable or personal value, then if you can shave off three minutes on your transit time, you have paid for a gallon of gas.

Comparing costs of all types of transport (public etc.) using public transportation is quite expensive. Coming from suburban Boston, you typically lose about three hours per day between getting to train station, train, subway, walking. since transit time has zero productivity, those hours are expensive on a personal and professional level. using a $60 per hour rate, in this scenario, public transportation costs you $180 per day versus $100 plus or minus you will lose with car transport. the model gets even worse on evening and weekend times when the schedule is reduced.

on the value of time, economists have done a good job figuring out how much time is worth to people and typically the premium is about two to three times what they make for a wage. A high wage earner is more likely live in the distant suburbs then a poor person. therefore the value of avoiding public transport, driving fast, and avoiding urban centers is increased.

Liter for Liter comparison of diesel to gasoline is not fair and misleading. Diesel vehicles are actually 40% more effecient with fuel economy. So the diesel vehicle will not consume the same amount of fuel for the same given distance. It actually takes more energy to make gasoline than diesel. Diesel fuel and kerosene heating oil is made with byproducts of gasoline production. Where all diesel vehicles receive there bad press is from the fact that diesel vehicles are only as good as the fuel put into them. The diesel fuel of the 70s and 80s had 6000ppm sulfur content, hence the high CO2 and NOx. Even in the early 90s that was only lowered to 600ppm in most places. This alone was enough to lower most CO2 emissions to lower than that of equivalent gasoline engines. NOx emissions still are slightly higher than gasoline emissions. This can be verified by comparing any emission reports between equivalent vehicles (www.fueleconomy.gov).

Smart cars that communicate with each other could allow drafting and save fuel.

Eric S. Johansson, we don't care what your time is worth. Just drive a more efficient car!

Oh, if "Automotive Testing Papenburg (ATP) 12.5 km high-speed circuit in Germany" has long sweeping turns, then I can believe their numbers for their course. The numbers might even be good for comparisongs between cars (over the equal course), but:

the numbers drawn on a curving track are not going to be directly applicable to our highway driving experience.

FWIW, it looks like Papenburg is a long oval:

http://www.atp-papenburg.com/D/I_01.html

The circular looking ends look like they could scrub tires on all cars and cost MPG.

"Under these conditions, it's impossibe for the Police to do anything. They don't even try. In fact, if they are dumb enough to get on the expressway for anything other than an accident response, they cause trouble."

OK hon, pack up the truck we're moving to 'hot'lanta!

Ya its a totaly useless test. Anyone who knows how to get fuel savings going fast knows its BEST when the road is completely straight and level or at least has extremely wide turns.

Thats because you have to get into overdrive and stay there AND you need the right overdrive gear. Most cars now adays have overdrive gears made for passing not for cruising.