© Author(s) 2006. This work is licensed under a Creative Commons License. Atmospheric Chemistry and Physics

Abstract. A methodology to acquire valuable informa-tion on the chemical composition and evolution of vehicu-lar emissions is presented. The analysis of the gases is per-formed by passing a constant flow of a sample gas from the tail-pipe into a 10 L multi-pass cell. The absorption spec-tra within the cell are obtained using an FTIR spectrometer at 0.5 cm−1 resolution along a 13.1 m optical path. Addi-tionally, the total flow from the exhaust is continuously mea-sured from a differential pressure sensor on a Pitot tube in-stalled at the exit of the exhaust. This configuration aims to obtain a good speciation capability by coadding spectra dur-ing 30 s and reporting the emission (in g/km) of both criteria and non-regulated pollutants, such as CO2, CO, NO, SO2, NH3, HCHO and some NMHC, during predetermined driv-ing cycles. The advantages and disadvantages of increasin