Turn up and Go mechanics

There are more knowledgeable Scotland Ferry folks on the forum than me but I won't let that stop me from opining. My experience in 2019 on the Lochranza-Cloanaig ferry without a car reservation was to get there early, get in line and dink around Lochranza castle while I waited. But I used to live on a ferry dependent island in the Puget Sound. So I'm used to arriving early when I absolutely need to be on a particular boat. And yes, an overload for a particular ferry is an overloaded ferry and those who don't get on get left behind.

Thanks for the reply, but that wasn't the question. I always get reservations, but it's sometimes dicey deciding which ferry to reserve due to travel time variables, etc. If both "regular" reservations and TUAG reservations are available, why should I constrain myself to a specific time? I'm presuming Stuart will chime in.

I'm also a frequent traveler on WSF, and I never count on just showing up. It's pretty easy to get reservations if you understand the phased release system and as a last resort, the cancellation deadlines.

Sorry, I'm not familiar with TUAG tickets. I just thought you meant not having a reservation. I'll just fill in with what we did on our way to Arran from Ardrossan. We were flying in from Dublin, renting a car at Glasgow and had reservations that night in Brodick. Since there could be flight delays (thank you Ryan Air), didn't know how long it would take to get a car (Arnold Clark is very fast and prompt) and had never driven from Glasgow to Ardrossan I didn't want to risk not getting on a sailing. So I reserved for the last sailing. We arrived in time for the penultimate sailing. The ferry line was almost non-existent and when we got to the booth the ticket taker took our reservation and said there would be no problem getting on that sailing.

On a TUAG route like Lochranza there are not also fixed reservations. Every one is on an 'if there is room' basis.
So if you are going on to, say Islay, where you do have a timed reservation, you essentially need to use the ferry before the one you would really want and kill time on Kintyre.
On Lochranza I would turn up especially early if Brodick has disruptions as lots of traffic will be diverting. Yes they will try and send a 2nd vessel round or make sailings an untimetabled shuttle when that happens to clear traffic, but still.
The Portavadie ferry is often "borrowed" as the 2nd vessel when that happens, or the Loch Bhrusda (fleet relief vessel) sent over.

Likewise Fishnish if Craignure is disrupted when the Tobermory ferry is sometimes "borrowed" to clear traffic.

Basically on such routes capacity in normal times is expected to exceed demand.

Going back to the admittedly way larger WSF ferries they are all TUAG, I believe, except the San Juans. So on peak days like Thanksgiving from the reminders I get from WSF on such dates they just say you may be in line longer than planned.
It may be a bad comparison, and I get a sinking feeling I will be corrected, but it's the best I can think of.
If I am talking rubbish on WSF and have mis read it so be it.

Thanks for the clarification. I thought I had done a dummy reservation from Lochranza and been given a choice of specific times, but that was last summer, and maybe things changed or I misremember. My plans do not include a timed ferry at the end f a string, but that was just a stroke of luck, not clever planning.

I only use the San Juan and Port Townsend ferries and I believe you're correct about all the other routes.

Technically all the CalMac ferries are 'TUAG' for foot and car passengers, just that capacity on the networks mean they are not. One of CalMac's current ferries was built with a capacity of 130 cars, it now has a capacity of 90 as cars have gotten larger.

On the larger routes the TUAG slots are generally reserved for islanders heading out or heading home. Only if there are none they will then go on general sale, so it can't be guaranteed, and the slots are not always guaranteed for islanders. It is always best to get a reservation where available.

On smaller ferries, like ones mentioned, and the Gourock Dunoon ferry it really is TUAG. Just, once it is full, it is full and you are looking. I've watched the car tetris on that ferry a few times, the skill filling the ferry is impressive. And you can often see the body language of those who have just missed this ferry, and have to wait the half an hour or hour for the next one.