{'fraction_non_alphanumeric': 0.018867924528301886, 'fraction_numerical': 0.00776914539400666, 'mean_word_length': 4.934210526315789, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Comparative Study of Motorcycle Helmets Impact Performance

Two sets of new and in-service helmets were impact tested using a drop test machine, in accordance to established helmet test protocols. The first test for full helmets was executed in compliance with standard speed requirements of 5.9 m/s in which three of five new helmets performed poorly. The second set utilized lower impact speed of 4 m/s for individual helmet components test. New helmet liners absorbed 5 times more impact energy than the in-service liners while the new shell was 19.3% better in dispersing impact energy than the in-service shell. The undesirable changes in liner thickness have explicit effect on the liner density which is translated into reduction in energy absorbing potential. In brief, exposure to weathering stresses and use intensities has affected helmet impact performance, regardless of service duration.