A fleet of 435 new propane-powered school buses will begin transporting students next month in two Nebraska districts. The Omaha World Herald says the buses that will serve the Omaha and Millard school districts will be the largest propane school bus fleet in the country. The two school boards approved a four-year, $25 million-a-year transportation contract with Student Transportation of Nebraska. The Omaha portion will be $19.5 million a year, an annual savings of about $300,000 a year from the previous contract. Millard will pay the remaining $5.5 million.