Making Quieter Highways

An anonymous reader writes "Researchers at Purdue are investigating ways to make life for those who live near major highways more quiet. They have found that most of the noise is literally where the rubber hits the road, not engine noise or even passing winds. The team has come up with a new form of pavement that is in testing in Arizona and will soon be installed in California. The pavement is simply asphalt with some mixed in rubber."

I hope to god they succeed

[PeteyG]

I lived next to Interstate number 5 last year, and it was like a constant dull roar coming in through the windows. After living for years in the quiet peace of Alaska, it was quite a shock.

If all the noise is from the rubber hitting the road. We need magnetic cars!

They've only just figured this out?

[gazbo]

On the A31 near where I used to live there is a stretch that is done in a noticeably darker (and smoother) tarmac. I think it was done specifically for noise reduction, and when driving over it you can really tell - it's a tremendous difference. Like you know if you're in a room with a washing machine and it finishes, and suddenly you're aware of how quiet everything is? Same sort of effect.

Now I'm not saying it's the same stuff, but is it really a new finding that it is the tire/road contact that's noisy when this was done at least 6 years ago?

Where do you think we are?

[BoomerSooner]

Europe?

Seriously though I agree completely with your statement. However, common sense has long since left our government.

Still recyclable?

[Xunker]

One thing the article doesn't touch on is reusability. One thing that the paving industry likes to pride itself on is that asphalt is almost totally recyclable. However, to my understanding, dense rubbers (such as car tires) aren't reuasable in that way, they can't be melted down and reused with reliability. Would the addition of the rubber have a problem with the recasting of the asphalt? With the amount of repaving that happens every year, what sort of effect will this have on the waste output of a repaving operation?

Re:Coefficient of friction

[n1ywb]

Not necessarily. One thing that we overlooked was the difference between static and dynamic friction. Static friction tends to be much greater than dynamic friction. When two bodies are stationary against each other, you've got static friction, EG a tire rolling down the road. Dynamic friction is when two bodies slide against each other, EG a tire skidding on the road. So since the friction between the tire and the road is usually static, it shouldn't really effect efficiency much since at the contact patch the tire is actually stationary relative to the road. However we know that the tire flexes and rubs against the road a little bit so more friction could possibly reduce efficiency slightly. Although cars tend to get worse efficiency on dirt roads, so I dunno. Of course with stickier roads, you could conceivably get away with a smaller contact patch by using harder tires, which would really improve efficiency. Harder tires == better mileage, due to lower rolling resistance. So I guess the real question is, how much of the energy lost in a tire is due to the edges of the contact patch rubbing the road, vs. the heat lost by the tire flexing as the patch rotates around it. I'm going to guess that since tires can last 50,000 miles, the effect of the contact patch friction is really negligable, and the flexing of the rubber as it rolls is the greatest source of loss. Hence a stickier road would not decrease efficiency, but you could use harder tires on it and increase your efficiency, although you would lower your friction coefficient somewhat, but it would probably be worth the trade off.

Re:liars and thieves

[passthecrackpipe]

If you would have looked at the content of my post, you would have seen that it concerns a mixture of asphalt as well as concrete. ZOAB technology is now about 15 years old in backwards Europe, so we have gone ahead and recently invented a 2 layer mixture, where the top layer has a higher density then the bottom layer. this greatly reduces sound pollution, and has a much lower requirement for maintenance. It is also more environmentally friendly. To top it off, pun intended, there is a topcoat of a mixture of different polymers that act as a filter, letting water through, but at the same time keeping freezing temperatures out, doing away with the "black ice" phenomena - you know, a thin sheet of ice that is invisible, until you see the big pile-up ahead of you? It also reduces sound pollution more, but is more expensive.

I checked with a mate of mine that actually works on this stuff, and latest I heard, some USians are coming to see how it is done. We stopped playing with rubber about 25 years ago. Soon, you will learn that GSM makes for better cell networks, PAL is the better display standard, Open source is the way to go for software development and deployment (Europe leads the way in terms of OSS deployment, in terms of percentage as well as hard numbers.) and various other "Mysterious Happenings From The Future"

Blind anti-americanism, just because I think the US is silly for not adopting existing, tried and tested technologies - from their allies, of all things - rather then re-inventing the wheel? A troll, I say. Anyway, next time you need a "coalition partner" to give your oil-grabbing excercise a veneer of legitimacy, it will probably be an EU country you will be turning to. Eurotrash Indeed....

Not the problem, or the solution

[flikx]

The real problem is the fact that idiots continue to build and buy homes next to busy highways; airports too. If you don't like the noise, don't live there!

Fairly obvious if you ride bike

[sporty]

I don't mean a motorcycle either. Try riding a mountain bike at some decent speed. Eventually, at the right speed, it hums quite nicely.