Having a wood handicap ramp and deck built?

Anit-slip tape on the ramp 2-3" wide strips every 6 inches. The deck you could paint/stain and use anti-slip compound in the paint ( it is like sand) so the entire surface would be anti-slip.

Strips of the same stuff they use on skateboards is sold by the roll for outdoor use. But you can apply non-slip decking stain (clear) as a cheaper and less noticeable option. Cuprinol do one, but there are others. The ramp should be no steeper than 1 in 12 so you don't need a huge amount of traction.

The marinas around here often use metal mesh screwed down. People use roof shingles, fastened with roofing nails or screws and washers. You can buy self-adhesive non-slip tape. There is an additive for paint that can make any paint non-skid. Some outdoor carpet is pretty non-slip. Best thing to choose may depend a lot on your climate and your budget. I mean, will it be wet often, or will you have to shovel snow off it? How much use will it get? Are you okay with replacing whatever it is every so often, or do you want it to last years?

Vinyl deck covering might work too. The one I have has a rough texture that's quite non-slip.

Use what marine dock builders use.

They use anti skid decking like "Skidguard" and "Tuf-Tred"

The tapes just peel off and shingles aren't designed to be walked on so they quickly loose all their grit