Clearly, nothing constructive has happened since an old article of mine on the same subject ("A National High-Speed Rail System: The Task for Engineers," IEEE Technology and Society, Winter 1993). I mention the same corridor proposals you do, but there is nothing new other than the New Haven-Boston electrification, which should have been done decades ago.

You cite the "dedicated" tracks required for really high speeds. Why is this a problem when, in your more upbeat treatment of maglev, completely new and incompatible rights of way would be needed? The real problem is that in the wholesale abandonments that have cut the U.S. network by over a third, many alternative routes were cut or torn up that could have served as freight routes, while others were upgraded for high speed.

The "gauge-change" train you mention isn't new either; the method of independent wheel traction has been used for years on the French-Spanish border.

"Hotfoot for the Iron Horse"? It isn't even cold comfort.

Is that correct? The last I heard, three other nations were using the old British system: Burma and two others on which I am hazy; perhaps Liberia was one.

The reason I bring this up is not because I am against metrication (I think it is appalling that U.S. engineers are afraid of the challenge of the changeover, and would rather continue with errors and loss of exports), but because I wonder if perhaps you are too passive in your publication of letters to the editor. I know it is a tricky endeavor, but if you don't correct falsehoods in those letters, you know that most readers are going to leave them believing misinformation.

Temperature charts are now available going back 150,000 years and they show that it has been going up and down all the time. The phenomenon is clear: Global warming and cooling happen. The question is the mechanism: Is it trapping by CO₂? You can get a measure of this by running the numbers.

The only thermal trapping molecules present in sufficient quantity in the atmosphere are CO₂ and water. In now-standard sources, such as Hottel and Egbert in Trans. ASME, 1941, and rechecked in the 60 years since then, these gases are shown to have substantially similar emissivities. Their influence, therefore, depends on their concentrations.

For CO₂, the standard tables give this as 0.00032 mole fraction in dry air. For water, at an average of 50 percent relative humidity at 60°F, the standard psychrometric chart gives about 0.0055 lb. water/lb. dry air, or 0.00885 mole of water/mole (dry) air. This is close to 30 times the CO₂ concentration. The CO₂, therefore, is just "noise" in the water variations.

In view of the potential for wrecking the economic and social system by needless changes to fuel use to reduce CO₂ emissions, wouldn't it be worth a little time spent in rerunning the numbers to see if it is really necessary?

First, the Earth is a ball in space with no way to eliminate heat except via radiation. While there could be partial temperature rise mitigation through increased evaporation of water and melting of ice cover, the very fact that the Earth is becoming more industrialized and populous means increased heat is released to the environment. One only has to look at the increase in worldwide power generation and other use of fuels, both fossil and nuclear, to realize that we are pumping ever-increasing amounts of heat into the water and air.

While we are busy doing this, destruction of vast quantities of forest is consequently destroying the very agents that would at least mitigate the alleged greenhouse effect of increased carbon dioxide concentration. In order to rid itself of the increased heat, the Earth has to get warmer.

Our own EPA tends to aggravate the situation by continuing to specify emissions restrictions for power generation in terms of parts per million of exhaust gas. This can discourage attempts to increase efficiency. Power plant emissions should be based on weight per kilowatt-hour or megawatt-hour. One would think they would have learned from their earlier disastrous regulation of automobile emissions as ppm rather than weight of emissions per mile.

Just as automobile makers decreased volumetric-based emissions by engaging in designs that employed techniques that drastically reduced engine efficiency, present power plant operators can decrease some pollutants by fuel/air ratio adjustments that are detrimental to efficiency. This results in decreases to volumetric pollutants, while increasing the wasted heat and, frequently, the actual weight of pollutants per kilowatt-hour.

The article states that in head-on accidents the passenger vehicle crosses into the truck's path eight times more often. However, the article fails to note what the expected rate should be. In the National Highway Traffic Safety Administration's statistics for 1997, trucks accounted for 7.4 percent of 2,560,372 million vehicle miles traveled. If you assume that vehicles and trucks have the same crossover rate and normalize for the vehicle miles traveled, you would expect that passenger vehicles would be 12 times more likely to cross over into a truck's path, because they account for 12 times the traffic.

The conclusion it appears Daniel Blower is trying to support with his statistics is that trucks and truckers shouldn't bear the responsibility for improving highway safety because it isn't their fault.

I suggest a systems engineering approach to the problem of highway safety by taking action where it is most effective. While many of these changes would involve automobiles and the roadways, many of the most effective ones would lie with reducing the speed of trucks, increasing traffic separation by restricting lanes available to trucks, and mandatory truck system improvements.

If you look up the University of Michigan's Transportation Research Institute on the Internet, you will find that Blower is associated with the affiliates program for the Center for National Truck Statistics. The affiliates program's sponsors are Freightliner Corp., Volvo-GM Heavy Truck Corp., Navistar, Insurance Institute for Highway Safety, Owner-Operator Independent Drivers Association, and American Trucking Associations Inc.

As I read, I wondered, "What were the contributions of Skalak, Lissner, and Fung? How do mechanical engineering and cellular biology meet as in the early development of cryobiology?" A few anecdotes would have added instructive detail, and also would inspire the imagination of the reader.

To make room for such illustrative details, many broad generalizations could have been eliminated, as well as the chronology of institutional funding without saying what each institution's contributions have been.

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