We present results from a series of experiments, where relevant factors for theuse of path prepositions were examined. We were especially interested in the concepts behind the German prepositions "entlang" and "vorbei" (similar to "along" and "past"). After exploring the basic properties human beings attribute to these prepositions, we systematically varied those properties to investigate their impact on the selection process and the corresponding speech production latency. The results indicate that parallelism and distance between the outline of a reference object and a trajectory are key concepts in this context.