John C. Freytag - Comments

The proposed amendment to the bus noise testing regulation states "In its earlier NPRM, FTA noted that the test data might not reflect the actual performance of these buses in real-life service." This is in reference to the weight loading and operational conditions addressed in the proposed amendment. However, my recent experience with a hybrid bus operation revealed another situation where test data might not reflect the actual performance of the buses in real-life service. Certain hybrid buses employ capacitor banks in lieu of batteries for electrical storage. The intermittent charging of these capacitor banks is extremely loud and tonal, producing sound levels well above those of normal bus operation. Unfortunately, it does not appear that the proposed amended noise testing regulation would address the noise from intermittent charging. The capacitor charging of these hybrids is controlled by load demand and is therefore unpredictable. A much more complex noise testing procedure may be required to determine both the sound level and frequency of occurrence of capacitor charging. The sound level, frequency of occurrence and duration are required to perform an acoustical assessment of this hybrid bus operation. Thank you for your attention to my comments on the proposed amendment, and please excuse my tardiness in responding.