Duragrouch

I agree with the above regarding a Bike Friday; Its problem as a frequent folder is that it has more loose parts when folded and *disassembled*, like the handlepost. Folded, it's not all one-piece.

With a full-size coupler bike, I think even worse. With the wheels on, still pretty large just folded in half, and with wheels off, more separate pieces.

For multi-mode transport, a Brompton reins surpreme, due to it's very compact fold, plus the added bonus of the chain folding to the inside between the front wheel and frame, so far less chance to get anything oily (although a frequent folder is a perfect application for chain waxing instead of lube). A Brompton is small enough to keep beside you or put in the overhead shelf on a train.

However if you don't need to lug a folder far or keep next to you on a train, a "bi-fold" folder bridges the gap for the two above. My Dahon 20" wheel folder, when unfolded, is nearly indistinguishable from a Bike Friday NWT. But it folds different. You fold down the handlebar, you drop the seat post (which also acts as a "landing gear"), and then fold the frame in half laterally, there is a hinge there. Bulkier than a Brompton (I think about 50% longer and 50% taller), but all one piece. Both wheels stay on the bike. The rear triangle doesn't "swing" underneath like a Bike Friday, so the rear rack stays on top and doesn't need to be removed. It's a "neater" fold. (Though the drivetrain is still on the outside, like a Bike Friday.) The added benefit is that, like the Bike Friday, it's fully tour capable. Again, pics of mine below, on the train (in baggage area at end of car) and in tour mode; From baggage to tour, or the reverse, 5 minutes; I need to take off and reattach the aero bar forearm pads, they impede the fold, and panniers and trunk bags on or off. Without panniers, the bike folds or unfolds in 15 seconds. Car fit: Dahon website has folded size of the Mariner, extremely close folded size to my Speed D7. I scienced the heck out of my build, it travels train or car well. 2X crank is not original! That's an upgrade I had to do myself. Other similar folding bikes: Several Zizzo models, and the Origami Bull which has fatter tires, disc brakes, and a front derailleur bracket to go 2X on the crank (I had to add one), both way less cost than a Dahon these days.

Now if I go air travel, I'll have to pull the wheels off and bike apart, to fit in checked luggage, possibly in two different parcels to each fit under 62" max girth.