DALLAS — The purchase of an average-priced new vehicle took even more weeks of income in the fourth quarter of 2008.

In response, consumers are adjusting the types of vehicles they are looking for.

More specifically, Comerica Bank's Auto Affordability index found that the purchase took 22.8 weeks of median family income.

This reading is up 0.5 weeks from revised third quarter affordability of 22.3 weeks, but down 1.3 weeks compared with a year ago.

Reflecting a sharp rise in the average interest rate paid on car loans, the total cost of buying an average-priced light vehicle was $27,700, up from $27,160 in the prior quarter.

Also contributing to the erosion in affordability, median family income is estimated to have edged down 0.3 percent in the fourth quarter, its first decline since first quarter 2002, officials pointed out.

"The underlying data shows quite clearly that car buyers are facing stringent financing conditions," said Dana Johnson, chief economist at Comerica Bank. "In the latest quarter, car buyers had to put down bigger down payments, pay higher interest rates and limit the maturity of their loans.

"People in the market for new cars also reacted to the difficult environment by choosing cars with lower sticker prices. The average amount spent per car dropped 2.4 percent in the latest quarter," he added.