By 2011, the number of U.S. autos with iPod adapters is expected to reach 28 million from 500,000 this year, according to the Telematics Research Group. Worldwide, iPod support is expected in 73 million vehicles in six years from 900,000 this year.
"The rapid ramp up of available solutions from automotive OEMs (original equipment manufacturers) is a stark contrast to the normal five-year product development cycle in the automotive industry," Phil Magney, founder and principal analyst for TRG, said in a statement.
Currently, 39 models from major U.S. auto brands are sold with either iPod adapters or an auxiliary-input jack for plugging in some other digital audio device.
Aux input jacks are expected to ship with 60 million cars in the U.S. by 2011 from 3 million this year. Worldwide, the numbers are 150 million and 6 million, respectively.
The number of cars with support for the wireless Bluetooth audio standard, or A2DP, is expected to increase from zero today to 8.5 million in the U.S. and 25 million worldwide in six years.