JL UK
Ah yes I should have mentioned the scale! I'm in HO scale, so I'd need a track plan that fits with that size.
I'm not limited to a 5ft length, but if it gets much beyond that it would become a bit too big to easily fit in my car. Perhaps if there are some good 6ft designs out there? :)
Thanks for those excellent links, I can see I'm going to be researching for a while yet before I find the perfect plan! I'm hoping to find something that works as a stand-alone layout, but could also be extended in the future, perhaps with the addition of 'off stage' holding areas or as part of a larger layout.
Just a suggestion - you are more likely to find something that will work well for you if you give up on the idea of "finding" a perfect plan, instead focus on what you want to model on your layout, and then design a plan made specifically for your needs.
That is especially important if part of your goal is that the layout later should function as part of a larger layout.
The standard two step process when starting on a layout design is:
1) define how the room where you will have your layout looks like - make a drawing of the whole room, indicate dimensions, doors and windows, and note what other uses of the room a layout will have to co-exist peacefully with.
2) Make a list of your givens and druthers for the layout. Givens are the factors you cannot (or will not) change - the stuff that are make or break - if you can't do things this way, you won't build a layout. Druthers are the things you would like to have, but you could conceivably compromise these if a better idea came along.
And important part of the list of given and druthers is your preferred theme, location and era. A 1910 mine in a desert landscape is quite different from a modern era industrial park, or a 1940s Mid-western small agricultural town.
Anyways - you may have spent quite a bit of time thinking long and hard about this, but just to be sure: you are sure about H0 scale being a given rather than an option?
I am not asking because I am opposed to H0 scale - I am in H0 scale myself. But if you actually are limited to a 5-foot long layout, N scale would give you a lot more options.
Quick illustration of a simple runaround in 5 feet of length in H0 and N scale, assuming a short engine (an SW7 switcher) and short cars (40-foot boxcars - i.e from the transition era, not modern cars):


As for transportation - what you seemingly are saying is that you need to be able to separate the layout into 5 foot (or shorter) sections. Why does the layout need to fit into your car - are you planning to take it to exhibitions or club meets or some such thing?
Also, if you have no idea or preferences about theme, location and era,
you are unlikely to have a large existing collection of usable engines and rolling stock
that are appropriate for your era, location and theme and which must be re-used.
Not trying to badger you into making this or that choice - it is your layout, it will have to suit your preferences, and in the end all choices are yours to make, of course. I just want to make sure that you have considered your options.
For micro layouts, every inch is important - there is not enough room for not making deliberate decisions about every design factor.
Smile,
Stein