Passenger cars are the major contributors to urban air pollution in India. Generally, emission factors are developed in a laboratory setting using a standard driving cycle. However, laboratory-based emission tests do not represent real-world emissions. This research quantified the CO, HC, CO2, and NOx emissions for a diesel passenger car using the portable emission measurement system (PEMS) in Sangareddy Town, India. A simple linear regression (SLR) technique was employed in this study to develop the speed-based emission models. The developed SLR models had higher accuracy, as demonstrated by the coefficient of determination (R^2), root-mean-square error (RMSE), and mean absolute percentage error (MAPE) values. In this investigation, emissions rates (CO, HC, CO2, NOx in g/s) increased as speed increased, and the emission rates were particularly high at high speeds (90-100 kmph). The result revealed that emission rates were found to be minimal at an acceleration range between -0.2 to 0.2 m/s2 at a speed range of 30–60 kmph. The observed emission factors (CO, HC, CO2, NOx in g/km) in this study exceeded the Bharat Stage (BS)-IV emissions limits. Analysis of speed and acceleration on tailpipe emissions will help policymakers understand emissions patterns in heterogeneous traffic and frame policies accordingly.