I will absolutely refuse to ride during the day without a strobe front light and a strobe rear light. I just wont!
Not a 'scientific study', but I noticed a definite difference in the attitude of automobiles/trucks to me after I started riding with strobes. My normal riding territory is in the 'high desert'. The Antelope Valley west and north of Palmdale/Lancaster, sometimes south and southeast on the north flank of the San Gabriels. (The roads east are really crappy and do not make for an enjoyable ride). The usual road condition is two lanes, one each direction, 8-10 feet in width, separated by a dashed yellow line, usually a fog line, but with only six inches or a foot of asphalt before dropping off onto a soft shoulder. In a few places, the shoulder is more, in many, non-existent. So, to ride out in the high desert means that you have to ride about six inches or a foot on the left of the fog line, in the path of fast moving traffic, (thankfully, field-of-view is vast and visibility obstructions are rare).
Anyway, before riding with lights, maybe one single car out of ten will go at least half-way over into the oncoming lane to pass me. The other nine out of ten? They pass so close that if I were to thrust my left arm out straight . . . well, I wouldn't have a left arm in that case, at least not a hand.
After starting to ride with strobes, that ratio flipped! Now, nine out of ten cars will move over into the oncoming lane and only the occasional, inattentive idiot will 'buzz' me. On one occasion, an oncoming car, signaling to make a left turn, stopped about a quarter-mile ahead of me and waited until I passed before turning. I couldn't believe that someone would wait that long! Of course, I gave them an appreciative wave as I passed.
These experiences have made me a believer! The only time I won't ride with strobes is if I'm on a MUP, (i.e., SART), or in a pack, such as on our Saturday morning bike shop sponsored rides.
And of course, I got the brightest lights I could afford. The less expensive, and dimmer, lights are just not visible in daylight, and marginally better than background 'noise' at night. You have to be seen!!! On the front, I use a NiteRider Lumina 600. Got some newer Luminas with higher Lumen output, but I don't like the strobe pattern of the new ones, so don't really use them. They flash too fast, and a phone call to NiteRider confirmed that the pulse rate cannot be changed. On the rear, I use a Dinotte Quad Red, (which replaced the previous model Dinotte that I lost on the road somewhere in my adventures). Both lights are USB rechargeable and good for an eight-nine hour ride. (The strobe function really extends how long a battery charge lasts. After I get home from a ride, one of the first things I do, even before jumping into the shower, is to put the lights on the charger so that they will be ready for the next ride.)
This has become a religion for me. There is no way you can get me out solo without strobes, and those don't ride with them . . . well, they just don't understand that it's a battle out there, and we cyclist are undermanned and outgunned. We need all the aids available to us to increase out visibility. If the 'enemy' can see us, then the probably won't hit us.
Sorry to be so adamant. It's a serious problem in SoCal, and other places that don't understand the danger they pose to cyclist or just don't care. One major reason that when I retire next March, I'm relocating to Idaho. They 'respect' cyclists up there, (based on my own, personal experiences while cycling in the state).