Fences mean nothing to a cat so that won't keep one off a road. Indoor-only cats are mentally healthy and can live a long, physically healthy life protected from attack by other animals, injury and exposure to life-threatening diseases like FIV and FIP. What they don't know about they don't miss.

The idea of a enclosure is a good one. If constructed properly it can provide access to the "outside" and provide security as well. I know two European cats who are indoor-only with one walked on a harness. She looks forward to the walks but expects the harness. She knows the rules.

My dear Dant้ was rescued from the street and didn't ever want to go back out. He spent his days on a protected balcony where he he watched the world go by or snoozed in safety and comfort. That was enough for him. His serious sleep was reserved for inside on the bed anyway.