The outdoor drive-by test has been part of the standard measurement procedures in the automotive industry for decades. Numerous measurements and publications of results and procedures have focussed on the sound radiation of the moving vehicle and the comparison of results with actual laws and test codes. ISO 362 is the most well known standard which sets the scope of the drive-by method, the instruments, accuracy and the description of the vehicle movement. The noise acceptance limits for various classes of vehicles have been steadily decreasing and will conceivably continue to do so. There is therefore an increasing need for efficient tools to quantify the main sources that contribute to the pass-by noise. A quick method for noise source quantification without having to modify the vehicle e.g. leadwrapping, is highly desirable. Moving source beamforming enables individual noise sources to be quantified at the ISO measurement position during a single pass-by. This paper describes an effective and flexible moving source beamforming system for noise source contribution analysis together with practical results obtained during external pass-by measurements.