Understanding complex behavior patterns in response to triggered forward collision warning system benefits localized user experience design, especially in safety critical scenarios from a cross-regional perspective. This paper studies driver response behavior patterns towards two alarm timings, in car-following scenarios with different traffic density. Data from 32 participants in China and 30 participants in Sweden were collected using a driving simulator. Differences were observed between China group and Sweden group regarding response behavior patterns, system acceptance and effectiveness. Seen from obtained results, Chinese drivers were found to steer more frequently than Swedish drivers in response to triggered alarm no matter what alarm timing or traffic density there were. Chinese drivers preferred later alarm timing than Swedish drivers. To better design regional-adaptive human machine interaction of forward collision warning system; some suggestions were produced based on obtained results.