With North American auto sales expected to reach 15-year lows by the end of the year and further declines expected as customers hold on to their cars amid a weakening economy, record fuel prices and rising car prices, some states in the U.S. and Canada are investigating plans to boost sales by giving incentives to customers to trade in their older vehicles.

Older, less efficient more heavily polluting cars are being encouraged off the roads in California, Texas and all across Canada, though each has differing levels of incentives to offer drivers of the aging vehicles.

In Texas, for example, drivable cars more than 10 years old can earn their owners $3,500 toward the purchase of a new car - provided the owner's income does not exceed a certain level. California does away with the income restrictions, but only offers $1,500 in incentives to cars that fail emissions test, reports The Detroit News. Finally, Canada will begin offering on January 1 $300 in cash or a discount on a bicycle or mass transit pass to those who trade in an older car. The Canadian program seeks to get 50,000 such cars off the roads over the next three years.

The incentives will not only clean up emissions but could also boost sales of new cars, though it's unlikely the $300 Canadian offering is enough to push reluctant or cash-strapped buyers over the hump. The Californian and Texan programs are more likely to induce new sales, though the programs are capped at $50 million and $45 million per year, respectively. That limits California's number of participants to 33,333 and Texas' to 12,857 at maximum benefit levels.

That may be enough to help cut emissions, but a combined boost of even 50,000 cars sold between the two states will not be enough to significantly alter the bottom lines at any of the major carmakers.