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On-board measurement is a powerful method to assess vehicular exhaust gas emission, since it enables the acquisition of instantaneous raw emission values in real-world conditions. While the vehicle emissions are subject to traffic and environment fluctuations, on-board measurement is a fast and economical way to generate data for fleet emission inventories, for instance. It is part of the mandatory testing for heavy-duty vehicles in the USA, as regulated by the USEPA. In 2004, Petrobras (Brazilian Oil Company) first experienced on-board emission measurements while participating in an international joint project, whose objective was to obtain information regarding the light-duty vehicular gas emission contribution to pollutant levels in some of the major Latin-American cities.

This paper presents a methodology proposed by the PETROBRAS Research Centre (CENPES) to simulate in a laboratory a route performed during field emission tests run with an on-board emission measurement system. It also includes the procedure followed to build the drive cycle and to implement it at the CENPES' Vehicle Test Laboratory. Laboratory simulation of local urban routes, for instance, allows analyzing the impact of a new fuel formulation on the emission levels of a local fleet with higher accuracy and repeatability, as the test conditions can be better controlled. The usage of on-board emission measurement systems is more expensive and is subject to fluctuations in the traffic conditions, making comparative tests more difficult. In order to generate the new cycle, data acquired during the field tests was used to determine speed profiles and an average speed distribution was calculated.

This paper presents a proposed methodology developed during a research project at CENPES - PETROBRAS Research Center, to simulate a typical urban traffic cycle in the city of São Paulo on a chassis dynamometer. This cycle can be used in pollutant gas emission tests for light duty vehicles in laboratories. The implementation of a representative city cycle in a laboratory allows its simulation under controlled conditions. It can be applied, for example, in emission inventories and the impact of air quality in public health studies, without the need for on-board emissions measurement equipment for field use. This kind of equipment is generally expensive and the repeatability for the same cycle can be difficult to achieve, mainly due to traffic variants such as the day of the week, time, and weather conditions.