I think you meant a ramp for the handicapped or handicapped people?
If so, it’s more like a ‘handicap ramp’. However, I won’t quite write it that way. It does sound right. I would say ‘a ramp for the handicapped or handicapped people’ or ‘handicapped people’s ramp’.
A ‘handicapped’ ramp is one that is somehow or somewhat ‘handicapped’, deficient, defective, unusable or ‘disadvantaged’!? I don’t think that’s what you meant. At least I won’t describe a defective ramp that way.