Trucks built before 1994 would have to meet 2007 nitrogen oxide emission limits, according to a draft proposal released Aug. 17 by the California Air Resources Board, Transport Topics Online reports. The rule would be phased in annually, eventually covering all trucks in 2013. The Environmental Protection Agency’s 2007 heavy-duty NOx limit is 0.2 grams per brake horsepower-hour. Trucks would be able to use several methods to help meet the standard, including using diesel particulate filters, NOx catalysts and alternative fuels, such as biodiesel, CARB said. Click here to see updates on the hearing.