Up until July, I allowed my four cats out during daylight hours (well, between about 10am and 4pm). They had a cat flap that would read their microchips and was set to a timer. I was a bit worried about cars (more worried about dogs and people who might take them), but I live on a hairpin bend of a 20mph rd. Kids play out and I thought my cats would be safe.
One of them (my eldest cat, 5yrs old, v sensible and road aware) was hit by a car who didn’t stop, in the middle of the day.
I keep my remaining 3 indoors now. The first catio went up over my front door within a week of the accident. I’m having a larger catio made and put on to the back of the house as we speak. The cats have lots of wall obstacles to climb (all over the house), cat trees, toys, scratching posts etc. They’ve also got two litter robots.
The stupid thing is that in the past year or so, I toyed with the idea of having catios put up but thought I was being over the top. I wish I had listened to myself and had the catios installed.
I think everyone has different situations though, so do what is right for you/your cat. Mine have transitioned well to having the catio and seem to enjoy it (as they can access it anytime day or night).