Sunday, May 22, 2005

Q Dear Tom and Ray:

I have been wondering about the safety of hydrogen fuel cells and the cars that plan to use them. While I'm sure that the volume of the stored fuel would be less than for, say, the space shuttle Challenger, I know that hydrogen is extremely flammable in the presence of oxygen. I am wondering if a traffic accident with one of these vehicles poses the potential for a conflagration? Have any tests been conducted? -- Walt

A TOM: Tests? Well, there's the Hindenburg.

RAY: Actually, the hydrogen in the Hindenburg was contained in a huge cloth bag -- not exactly the height of safety engineering. So that's not really a fair analogy to today's composite hydrogen holding tanks.

TOM: Hydrogen has some advantages over gasoline, too. In the event of a leak, it disappears very quickly -- and straight up, into the atmosphere, since it's lighter than air. It doesn't spill and hang around, and it's not toxic to humans and animals, the way gasoline or diesel fuel is. But given a spark, it certainly can create the world's most exciting Roman candle!

RAY: And yes, there have been real tests of the tanks that hold both liquid and gaseous hydrogen. Engineers obviously believe they are safe enough to be used in vehicles. Do we know, for a fact, that they're right? No.

TOM: Like most new technologies, on-board hydrogen has been tested in all of the situations in which engineers can predict it might fail. But inevitably, they can't predict everything. And there will be surprises once it comes into widespread use.

RAY: So I think, in general, hydrogen fuel cells will be safe, if and when they debut in cars. But I won't be surprised if we discover, with some unfortunate accidents, some ways they can be made safer. And personally, what worries me more than the cars are the refueling stations.

Dear Tom and Ray:

I am 16 years old, and right now I drive a 2002 New Beetle. But ever since I was a little girl, I've wanted a '68 Mustang convertible. My dad has always loved the idea. My mom, on the other hand, does not think they're very safe, because they don't have air bags, and some don't even have seat belts. So I was wondering if you could help me out a bit by saying that you can install seat belts and air bags in an old car like that. -- Alex

RAY: Well, we have to say your mom is right, Alex. While it did have lap belts, by today's standards the '68 Mustang is a terribly unsafe car. It handles horribly, brakes poorly, rides like a buckboard, has almost no structural crash protection and has none of the safety equipment that your 2002 VW has. It also drinks gas the way my brother drinks espresso macchiatos.

TOM: Can you retrofit air bags and shoulder belts into a '68 Mustang convertible? I suppose anything is possible. But it's completely impractical, and would be enormously expensive. Just for fun, we calculated the cost of installing all this safety equipment, and the total came to $23,890, which happens to be the base price of a 2005 Mustang convertible. So, do whatever you think is best, Alex.

Got a question about cars? Write to Click & Clack in care of The Post, or e-mail them by visiting the Car Talk Web site athttp://www.cartalk.com.

2005by Tom and Ray Magliozzi and Doug Berman