Funnily enough I'm familiar with the Ardrossan crossing, it's part of the branch from Ardrossan South Beach station down to the Harbour. For many years the crossing at Princes Street had full barriers but shortly after the line was electrified in the mid 80's there were a LOT of alterations in the lines. Many of the sidings and secondary lines down the harbour were removed, and the gates were removed, not to be replaced by half barriers, but nothing at all. There did use to be freight traffic in addition to the passenger service but with the removal of the extra lines it was down to an hourly EMU service, but still....
Especially with some of the idiotic drivers we have nowadays.