I don't ride ACH/Big Tujunga/Angeles Forest highways much, but do commute "over the hill" every day to and from work". Visibility has never an issue where it affects bicycle speeds, except for maybe if you go bonkers downhill. There are white fog lines painted on all the highways up there. The only thing you need to be cautious about is rocks and debris that fall down onto the road. Again, not a problem when climbing, but something to watch for on descents.