There are several standard accelerated weathering test methods used for geosynthetics which are required to produce the equivalent degradation results even though the light source, irradiance and spray conditions are different. Therefore, outdoor exposure and accelerated weathering tests were performed on polypropylene (PP) geotextiles using four different light sources for a better understanding of the effects of weathering. The test results obtained under four different test conditions for the combination of fluorescent UV, UV-A, xenon-arc and metal halide lamps are compared with natural weathering at the radiant exposure which is equivalent to one month exposure in southern Europe. Comparing to degradation observed from natural outdoor exposures enables assessment of the limitations, determination of the constraints, and interpretation of the data relating to accelerated weathering, all of which must be considered for service-life prediction.