Sometimes you just have to be aware and take into account the road conditions regardless of whether it's a public road, closed road, MUP, track, trail, park, whatever. Just because it's labelled one thing does not obviate you from making sure that conditions are safe for the speeds you're travelling. This includes watching for congestion points, other traffic, pedestrians, etc. Sometimes high speed cycling in congested areas is like attempting to run sprints in a shopping mall during the last weekend before Christmas.