Market research firm Harris Interactive’s AutoTechcast on Wednesday reported that almost two-thirds (65 percent) of adult automobile owners who also have iPods or other MP3 players use the device in their vehicles.

Other findings:

• Among all adult automobile owners, ownership of iPod/MP3 players is about one in 10 (12%).
• Over half (52%) of those who use an iPod/MP3 player in their vehicle, and 14% of all adult car owners, indicate that they are “extremely or very likely” to purchase an audio interface for their next vehicle.
• FM transmitters and cassette adapters are the least preferred.
• The respondents said they prefer connecting through an auxiliary jack located on the stereo head unit (39%) or through either Bluetooth (23%) or Firewire/USB connections (19%).
• Among all adult automobile owners, ownership of MP3/iPod players is about one in 10 (12%) and use in their vehicles varies considerably by age.
• MP3/iPod ownership is substantially higher (31%) among 18 to 24 years olds, and not surprisingly, ownership rates decrease consistently among older
  respondents, as low as five percent among those aged 55 and over.

According to Bryan Krulikowski, Senior Director of the Harris Interactive Automotive & Transportation (ATR) Research Practice:

"Vehicle owners 25 to 44 years of age are most likely to use their MP3 or iPod player in their vehicle. This means that vehicle manufacturers need to pay specific attention to the types of vehicles these buyers are interested in and equip the audio systems accordingly.

While new technologies and features typically trickle-down from luxury vehicles to mass-market vehicles, MP3 integration may become a 'trickle-up' feature given its young user base."

The study was conducted among 12,857 U.S. adults ages 18 and over who own or lease a vehicle, according to Harris Interactive.