Urbanisation has led to an increased need for mobility in public transportation. Sensing the unfolding worrisome scenario, many countries have taken up different mass rapid transit solutions to alleviate the problem and restore the free flowing traffic. BRT should have been the logical choice particularly considering the lower capital costs involved and faster implementation. Comprehensibly the expectations of this class of vehicles will be high in term of quality and comfort to the passengers. Level of vibration and noise is an important indicator to evaluate vehicle's ride comfort. The challenges are to design the high power Powertrain and Air Conditioning system nonetheless low interior noise, vibration and harshness correspondents to personal cars. This paper is an invention of, development work done in interior noise refinement of a bus. A prototype bus manufactured to meet all the requirement of BRT - premium segment urban bus. The prototype was almost meeting the entire required specifications, excluding interior noise and vibrations. The rear zone of the interior was the major concern of NVH levels, which demands to carry out the root cause analysis. There were various structure-borne and air-borne sources contributing to increase in NVH levels. Design and development iterations were conducted on the vehicle to achieve the well significant noise and vibration reduction and increased comfort to the passengers.