BENTONVILLE, Ark. --- In late 2005, Wal-Mart CEO Lee Scott announced a set of ambitious goals to become a more environmentally responsible company. According to a new AP report, the company's fleet of about 7,200 semi trucks is already about 15 percent more fuel efficient compared to two years ago. By late next year, that figure is expected to rise another 10 percent. The annual savings in carbon dioxide will be equal to taking 67,744 cars off the road. "We're real proud of where we've gotten to already," Tim Yatsko, senior vice president of transportation for Wal-Mart Stores, told the AP. Fuel efficiency certainly has its financial rewards. For each mile the company can add to its average mpg, Wal-Mart saves $35 million to $50 million a year, Yatsko told the AP. Today, the fleet averages about 7 mpg compared with a 2005 base of about 6 mpg. Great Dane Trailers is now developing a more aerodynamic trailer for Wal-Mart that the company hopes will further improve its fleet's fuel efficiency.