Headform impactor to bonnet top test is used to evaluate the safety of a car bonnet for pedestrian head in collision. In there, the headform impactor is used to replace the pedestrian head in test collisions. The test is performed by using headform impactor to impact to testing point on bonnet top. The level of pedestrian head safety is assessed through the HIC value is calculated based on the variation of the resultant acceleration of headform impactor center of gravity. In the formula for calculating the HIC value, the collision period time is currently limited to maximum of 15 ms. Furthermore, previous studies have shown that most collisions take place within about 10–12 ms and the post collision phase has a lot of noise that affects on the resultant acceleration. Therefore, using a collision time limit maximum of 15 ms will have many potential errors in the test results. This study will analyze how limiting the collision time to 15 ms affect on the HIC value. The results of this study are very significant in improving headform impactor to bonnet top test to be more reliable.