A few lessons here I think.
1) Don't believe everything you read from a law firm - they can over do things
2) Look closely at the wording and be critical of the way it is expressed
3) Check cause and effect
Yes turn signals are important to signify your intentions on the road, but I'm struggling to see that this is a primary or root cause of 2 million collisions. Note "collisions", not "accidents" as that is a more descriptive term. "Accident" implies that it's out of your control, when in the vast majority of cases it is in the persons control, but they lose concentration, fail to indicate, make poor judgements about speed and position etc.
Anyway I have filed out your form which has a few odd questions in it, so maybe road test those questions to see if you're asking the right thing.
Not sur eif you've seen it, but some cars now have some sort of detection device on the wing mirrors which lights up red or orange when there is a vehicle very close which could hit if you changed lane. Very useful.... You can even get retro fit ones. "Blind Spot monitoring" seems to be the correct search term.
I've definitely seen how not using signage can lead to confusion and even accidents. I filled out your questionnaire and hope that it will be useful for you. While working on my own school projects, I came across
https://personalstatementhelper.com/ and it is a great help for college applicants and students in general. It is exactly what I used when I was planning to apply to college soon. Good luck with your research and the rest of your engineering class. Projects like yours are really making a difference in raising awareness about road safety.
good luck.