Beginning June 1, 2006, all diesel fuel produced and sold for vehicular use in the 110 counties impacted by TxLED must meet a 15 ppm maximum sulfur limit, in addition to meeting all TxLED requirements. Vehicular use is defined by the TxLED requirements as on-highway vehicles, non-road vehicles (e.g. a farm tractor), and non-vehicular equipment (e.g. agriculture and construction equipment). Locomotive and marine vehicles are not included in the definition of vehicular use.