There are not barriers at Tring, nor indeed any practical way to add them without major building work as the entire station is outdoors apart from a small shed flogging tickets in the AM peak only.
I must admit to being surprised, though, that Break of Journey restrictions were not put in place to prevent this "misuse". Though I must admit I'm not waiting with exactly bated breath for one of the new contract security guards manning barriers to cause issues with doing this. I do support the manning of barriers at LNR stations for the full period of service, but I am disappointed cheap, poorly-trained security guards are being used to do this.