Just as commuters are catching up to the idea of satellite radio for their cars, former graduate students at Carnegie Mellon University have developed a next-generation radio concept that allows users to tune into music from iPods and other digital music players in nearby cars.

		Roadcasting A description of the project and a prototype version are available at www.roadcasting.org. The students made their codes for the prototype public, so others can revise the system, if they choose.

The idea, which the students developed for an unidentified "major automaker" last year, is called Roadcasting. Using it, you could tune your radio to music playlists coming from other cars within a 30-mile radius. Or you could transmit your own list of songs for people in other nearby cars to listen to.

Perhaps best of all, the Roadcasting software would learn what songs or musical genres you like. Using those preferences, it would sift through all the broadcasts available at any one time and choose the ones you should like best. Every time you turned on the Roadcasting apparatus, it would find an ad hoc radio station -- or create a mix of songs -- with your tastes in mind.

That kind of matching -- called "filtering" -- is what makes the idea special, and ties it to an important trend in how people are experiencing technology and culture.

Like the recommendation filters for Netflix or Amazon.com, which suggest products to you based on your past orders, the Roadcasting software would propose songs. With so many technological options for enjoying music, books and so on, such filters are increasingly becoming the way people pick through cultural content.

Additionally, concepts like Roadcasting are a logical next step for music playlists, which users already share all over the Web, including at Apple's popular iTunes site. The system, then, is something that unites people, contrary to the traditional image of technology being a cold or heartless thing.

"The Roadcasting system brings together people with common interests -- both musical and otherwise -- as the system also learns what radio personalities, commentators and podcasts drivers like," said one of its developers, Jim Garretson.

"As a result of this, communities can form around particular radio stations. The audience members are highly likely to enjoy the community they've found, since they have much in common with other community members."

Garretson and four other graduate students at Carnegie Mellon's Human-Computer Interaction Institute were commissioned to develop the system last year for the research and development arm of an automaker, with the hopes of introducing it to cars by 2010. (They are sworn to secrecy on which company, but HCII has a history of working with General Motors.)

The students, who since have graduated, finished the project last summer, but it has been getting attention lately in technology publications like Wired and MIT's Technology Review.

The attention seems tied to the buzz about podcasts -- largely amateur radio shows downloaded on digital music players -- along with interest in the developing wireless technology for cars and handheld devices. For the system to work, Roadcasting hardware and software would have to be loaded into vehicles. Also, users would have to opt into the network -- people would not be able to snoop through your music playlists unless you actively transmitted them on the network.

Even then, other users would not know which car you were in: The playlists, which are basically ad hoc radio stations, would only be identified by the name its amateur disc jockey gave it.

The technology is largely theoretical but would probably work like this: Besides having traditional radios or CD players, cars would also have a Roadcasting feature. When it is turned on, it would search for all the digital playlists being played nearby, probably over some kind of mobile Wi-Fi network, the same kind of technology that allows you to flip open your laptop and check e-mail at a coffee shop or airline terminal.

The Roadcasting screen would show song and DJ names, and music genres, then judge which offerings match your musical tastes. As you selected songs, the software would keep refining and learning about your tendencies, and would use them to find other songs that match them. Other listeners could listen to the same playlist and vote on songs at the same time, influencing what the ad hoc networks played.

Students at the Human-Computer Interaction Institute have done similar projects for a slew of companies, including General Motors, Texas Instruments, Sun Microsystems and Intel. The firms ultimately use about a third of the design concepts, after refining them, said Carnegie Mellon professor Robert Kraut, a faculty adviser on the Roadcasting project.

Some of the refinement on Roadcasting could be on legal or licensing issues for sharing the music among vehicles. The concept would not allow for downloads of music files, where most of the legal wrangling over peer-to-peer computer networks is now.

A spokesman for GM's advanced technology branch, Scott Fosgard, could not confirm it commissioned the Roadcasting work but said the company has long "worked closely" with Carnegie Mellon on "telematics," or tech-related products for the car.

The traditional radio industry of AM and FM stations is, of course, aware of the threats from emerging technologies like Roadcasting, said Sean Ross of Edison Media Research in New Jersey.

It has lately been pushing HD, or digital, radio technology, which can give listeners local information like weather and traffic tips, along with great sound. Later versions of HD consoles will allow users to purchase songs while riding in their cars.

Garretson, 24, now an interface designer and programmer living outside Boston, said the Roadcasting team is still working on the concept, and probably will try to make it work on handheld devices -- perhaps combination cell phone/mp3 players -- so it can be used in or out of the car.

"We're being told by a lot of people that this is the future of music. ... We want to get this thing into the hands of as many people as possible," he said.