I had a 20k commute to Dublin City Centre and/or across the M50 to Dundrum and Airside. Over the course of about 10 years, daily, in every sort of weather, I noted the differences in other drivers behaviour when I didn't wear a hi Viz jacket with and without sleeves, when I wore a fluorescent Sam Browne and wore no Hi Viz.
It was a pretty crude test as I only measured the different times to get to work in the morning and get home in the evening
I also experimented with the difference between having spots and having the full beams on ... ok I know I shouldn't!
I ride defensively and only filter below about 30 kph
The fastest times were were invariably with full hi viz and use of full beams and spot lamps.
The slowest times, and the most SMIDSY moments were without hi viz and only dipped lights.
Using a gilet type hi viz or a Sam Browne hi viz were better than none. Using high beams without hi Viz was only marginally better.
So, I always wear a hi viz jacket with sleeves, and, unless behind a vehicle, or at nighttime use high beams!