DART transit fleet represents leadership in clean fuels

In addition to introducing the Southwest’s first zero-emission transit fleet of electric light rail trains, DART has aggressively pursued a clean fuels program highlighted by new transit engine technology, liquefied natural gas and the creation of the ultra-low sulfur diesel market for Texas.

Thanks to the aggressive replacement of 710 buses since 1996, the NOx (oxides of nitrogen) emissions have been reduced by 701 tons per year. In addition, emissions have been further reduced by 258 tons per year as a through-the-exhaust gas recirculation (EGR) engine retrofit project. DART bus fleet emissions prior to 1996 were approximately 1,344 tons per year. The retrofit program was made possible by a grant from the State of Texas.

The combination of more new buses and the engine retrofit on hundreds of other buses in the fleet –allow them to benefit from the use of ultra-low-sulfur diesel. The net effect of these two initiatives will reduce current bus fleet NOx emission levels to only 385 tons per year. That’s good news in North Texas – an area with serious air quality problems.

The retrofitted buses, running on the ultra-low-sulfur fuel, will have emissions equal to or less than natural gas. This is an important transition phase for DART’s total clean fuels program. A major goal of the program is to begin operating zero-emissions buses by the end of the decade.

When DART began using ultra-low sulfur emissions fuel earlier this decade, it had to be purchased from refiners on the east or west coasts. Now, having created a market for the fuel, DART is able to purchase this fuel from two plants in Texas. Other transit properties in the state are also adopting this clean fuel. DART introduced liquefied natural gas fueled buses in 1998 as an initial phase of its clean fuels program. DART’s use of the fuel has received national attention and has provided valuable information the agency is applying as it moves toward its goal of operating a zero-emissions bus fleet.