Last time I did this for myself my rating was actually higher on the road. But I base my judgement on tournaments I attend, noting whether the home players dominated or whether the hottest rounds were by home players or visitors.
But your home-course advantage is fairly small---not enough to say a player who only plays tournaments at home will have enough of a higher rating to discredit the ratings system, which was the point.
Actually, there are 3 categories to consider---home course players, visiting players playing blind, and visiting players who've played the course several times and are fairly familiar with it. I doubt this 3rd group shoots much worse than the home course players.