Complex sentence: According to various published research, many factors (besides Age-21 laws) were shown to reduce USA's alcohol-related fatalities, including automotive-safety technologies & enforcement aimed at people older than 21.
Split into simpler sentences: According to various published research, many factors (besides laws raising drinking-age to 21) were scientifically shown to reduce USA's alcohol-related fatalities. These include advances automotive-safety technologies & enforcement aimed at people older than 21.