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Program-Wide Determinations on Bus Testing Requirements

The contents of this page do not have the force and effect of law and are not meant to bind the public in any way. This page is intended only to provide clarity to the public regarding existing requirements under the law or agency policies. Recipients and subrecipients should refer to FTA’s statutes and regulations for applicable bus testing requirements.

This page provides determinations that apply to the entire bus industry, or to multiple manufacturers, operators, etc. Older determinations that may be partly or fully obsolete are retained for reference on the Older Program-Wide Determinations on Bus Testing Requirements page.

2020 Ford 3.5L EcoBoost gasoline engine 

Ford introduced a new 3.5L EcoBoost V6 gasoline engine that replaced the 3.7L V6 gasoline engine in Ford Transit chassis. Since this is a new engine design, FTA expects it to produce significantly different data in the Maintainability, Performance, Fuel Economy, Noise, and Emissions tests compared to the previous engine.

Therefore, at least one bus model equipped with a 3.5L EcoBoost Ford engine must complete partial testing for Maintainability, Performance, Fuel Economy, Noise, and Emissions. A partial testing report with this data on a similar bus-powered by the 3.5L EcoBoost engine from any manufacturer will satisfy the partial testing requirements for a bus model equipped with the new engine. At this time, Bus Testing Report LTI-BT-R2020-02-P satisfies this requirement for the 3.5L EcoBoost engine, although as future buses are tested with this engine, the Partial Testing Report most representative of the baseline bus model should be used. (Posted June 1, 2021)

2020 Ford 7.3L gasoline engine

Ford introduced a new 7.3L V8 gasoline engine that replaced both the 6.8L V10 and 6.2L V8 gasoline engines in Ford E-Series and F-Series chassis. Since this is a new engine design, FTA expects it to produce significantly different data in the Maintainability, Performance, Fuel Economy, Noise, and Emissions tests compared to the previous engines.

Therefore, at least one bus model equipped with a 7.3L Ford engine must complete partial testing for Maintainability, Performance, Fuel Economy, Noise, and Emissions. A partial testing report with this data on a similar bus-powered by the 7.3L engine from any manufacturer will satisfy the partial testing requirements for a bus model equipped with the new engine. At this time, Bus Testing Report LTI-BT-R1914-P satisfies this requirement for the 7.3L engine, although as future buses are tested with this engine, the Partial Testing Report most representative of the baseline bus model should be used. (Posted June 1, 2021)

Buses submitted for testing without wheelchair lifts

Adding a wheelchair lift and associated additional doorway represent a worse-case with respect to structural integrity as well as installation and integration with the structure, electrical system and safety interlocks.  Effective June 1, 2021, a bus model that completed Structural Durability testing with a wheelchair lift and additional door may be offered without the lift and door, but a bus tested without a lift and door may not be offered with a lift and door without additional partial testing including Structural Durability and Reliability. (Posted June 1, 2021)

Buses manufactured on a gasoline-fueled third-party chassis and then converted to a liquified petroleum gas (LPG/propane) fuel system by a fourth-party converter, upfitter, and/or dealer prior to final acceptance of the vehicle(s) by an FTA recipient

A change in a previously-tested bus model’s fuel system from gasoline to propane is a major change and triggers Partial Testing requirements; tests in which FTA might reasonably expect to obtain different data (compared to the previously-tested baseline gasoline-fueled version of the bus) would need to be repeated. Accordingly, each newly-offered fourth-party conversion to a propane fueling system (consisting of a particular design, specific major components [whether produced in-house or by outside suppliers], installation techniques, and calibration) must have completed testing at the Bus Testing Center that includes at least the Maintainability, Safety, Performance, Fuel Economy, dynamic Noise (i.e., noise tests involving engine operation), and (if the conversion was contracted for testing on or after January 1, 2010) Emissions tests, since these are the tests in which FTA would expect to obtain significantly different data due to the conversion. Once a particular fourth-party propane conversion of a particular chassis has completed the testing specified above, it may be substituted for the corresponding gasoline chassis in bus models that have satisfied FTA Bus Testing requirements on that corresponding gasoline chassis. In this context, “corresponding chassis” means the same make and model chassis powered by the same make and model engine. Versions with fewer propane tanks could also be substituted, but versions with more tanks or changes to propane tank locations would require an individual determination of testing requirements. In order for a proposed propane-conversion bus model to meet the requirements of the Bus Testing Regulation, the Partial Bus Testing Report resulting from the test of the corresponding converted propane chassis must be provided to the recipient along with the full Bus Testing Report for the baseline gasoline-powered version of that bus model. (Posted June 1, 2021)

2018 Cummins “Near-Zero” and “Optional Low-NOx” natural gas engines

The FTA has evaluated the changes made by Cummins to its natural gas bus engines for model year 2018.  Cummins has indicated that the ISLG and ISX12G are being replaced in 2018 with updated versions that include a “Near-Zero” emissions package.  The Near-Zero emissions packages include changes to the engine electronic control unit, closed crankcase ventilation, and a larger and upgraded three-way catalytic converter. These changes reduced the EPA-certified oxides of nitrogen (NOx) emissions of these engines from 0.2 g/bhp-hr to 0.02 g/bhp-hr. The resulting Near-Zero engines are designated L9N and ISX12N, respectively.  Similar changes have been made to the ISB6.7G, reducing its EPA-certified NOx emissions from 0.2 g/bhp-hr to 0.1 g/bhp-hr. This version is designated B6.7N and is certified to the California Air Resources Board Optional Low NOx standard of 0.1 g/bhp-hr.

The CO2 emissions of these engines are projected to be approximately nine percent lower, corresponding to a similar improvement in fuel economy. The power and torque ratings are unchanged, and the weight differences of the engines and aftertreatment systems between the G and the Near-Zero/Optional Low-NOx versions of each engine are insignificant. In addition, no major changes are required in the mounting or interconnections of the engines to the vehicle. 

Based on this information, FTA has determined that bus models that have previously satisfied Bus Testing requirements when equipped with the ISB6.7G, ISLG, or ISX12G will not require additional testing when offered with the corresponding Near-Zero/Optional Low-NOx engine. 

The changes Cummins has made to these engines are limited to the 2018 emissions package, which is comprised of improved versions of mature technologies. While FTA would expect testing of buses equipped with the Near-Zero versions of these engines to result in approximately nine percent improvement in fuel economy data and approximately 90 percent improvement in NOx emissions data (50 percent for the B6.7N), these changes are in a favorable direction and they have been validated through engine dynamometer certification testing by the U.S. Environmental Protection Agency (EPA) and California Air Resources Board (CARB).  The FTA would not anticipate changes in other data measured during FTA Bus Testing of bus models equipped with these engines. (Posted February 6, 2018)

Buses manufactured on a gasoline-fueled third-party chassis and then converted to a compressed natural gas (CNG) fuel system by a fourth-party converter, upfitter, and/or dealer prior to final acceptance of the vehicle(s) by an FTA recipient

A change in a previously-tested bus model’s fuel system from gasoline to CNG is a major change and triggers Partial Testing requirements; tests in which FTA might reasonably expect to obtain different data (compared to the baseline gasoline-fueled version of the bus) would need to be repeated. Accordingly, each newly-offered fourth-party conversion to a CNG fueling system (consisting of a particular design, specific major components [whether produced in-house or by outside suppliers], installation techniques, and calibration) must have completed testing at the Bus Testing Center that includes at least the Maintainability, Safety, Performance, Structural Durability (test 5.7), Fuel Economy, dynamic Noise (i.e., noise tests involving engine operation), and (if the conversion was contracted for testing on or after January 1, 2010) Emissions tests, since these are the tests in which FTA would expect to obtain significantly different data due to the conversion. Once a particular fourth-party CNG conversion of a particular chassis has completed the testing specified above, it may be substituted for the corresponding gasoline chassis in bus models that have satisfied FTA Bus Testing requirements on that corresponding gasoline chassis. Versions with fewer CNG tanks could also be substituted, but versions with more tanks would require an individual determination of testing requirements. In this context, “corresponding chassis” means the same make and model chassis powered by the same make and model engine. In order for a proposed CNG bus model to meet the requirements of the Bus Testing Regulation, the Partial Bus Testing Report resulting from the test of the corresponding converted CNG chassis must be provided to the recipient along with the full Bus Testing Report for the baseline gasoline-powered version of that bus model. (Posted January 5, 2011)

Clarification regarding unmodified mass-produced vans

While unmodified mass-produced vans are categorically exempted from testing, this exemption historically assumed that unmodified mass-produced vans would only be offered in the 4-year, 100,000-mile service life category. FTA wishes to clarify that unmodified mass-produced vans are categorically exempted from testing only in the 4-year, 100,000-mile service life category; unmodified mass-produced vans offered in the 5-year, 150,000-mile (or higher) service life category are subject to testing. (Posted January 30, 2007)

Changing the primary structural material of a bus from mild steel to stainless steel will generally be considered a major change, and will generally require partial testing including the structure-related tests

The FTA considers changing from mild steel to stainless steel to be a “major change in chassis design” as defined in the Bus Testing Regulation that triggers additional testing. Compared to mild steels, stainless steels have different physical properties, different microstructure, and different (generally more stringent) manufacturing requirements.  Years ago, FTA allowed a bus model that had been tested with a mild steel chassis to be sold without additional testing with a stainless steel chassis; when the stainless steel model entered service, it experienced numerous structural problems. (Posted May 26, 2006)

Last updated: Tuesday, June 1, 2021