The transport sector is one of the major contributors to greenhouse gas emissions. This study investigated three greenhouse gases emitted from road transport using a probe vehicle: CO₂, N₂O and CH₄ emissions as a function of cold start and ambient temperatures. A real-world driving cycle has been developed at Leeds and referred as LU-BS, which has an urban free flow driving pattern. The test vehicle was driven on the same route by the same driver on different days with different ambient temperatures. All the journeys were started from cold. An in-vehicle FTIR emission measurement system was installed on a EURO2 emission compliance SI car for emissions measurement at a rate of 0.5 Hz. This emission measurement system was calibrated on a standard CVS measurement system and showed an excellent agreement on the CO₂ measurement with the CVS results. The N₂O and CH₄ were calibrated by calibration gas bottles. A MAX710 real-time in-vehicle fuel consumption measurement system was installed in the test vehicle and the real-time fuel consumption was then obtained. The Global Warming Potential (GWP) was evaluated using IPCC data for all three measured GHGs. The results show that N₂O and CH₄ can contribute to approximately 6~10% of GWP during cold start due to high GWP index, though their emissions were in a much lower magnitude. The influence of ambient temperatures on GHG emissions and GWP were assessed. The research provided a better understanding of traffic-related greenhouse gas emission profile in urban area and will contribute to the control of climate change.