This has been a big problem for many years. Whereas here in the Isle of Man, in general there is a realisation that it is dangerous, and the police stamp hard on transgressors, the NW, with its miles of fields by the course, and the problem of drunks, has always been scary.
To be honest when I go there, it is for the atmosphere in te paddock area, not the racing.. I'm not really into speed for itself.. I'd rather see the corner skills... for me the Man of the Meeting was Guy Martin, making up on the twisty bits the losses he made on the straights because his bike was so much slower (by he way, I am SO sick of hearing Steve parrish refer to "straightaways"... this is not America... they are "straights"!! Rant over!!!)
I remember in the early 90s seeing 2 drunks on top of the bridge/tunnel. They slept there the entire day, never saw a race, and must have had severe sunburn by the time they woke.