Roadtrip Romances

As I write this our family has embarked on what a friend of Mr. Grant has coined "the annual migration".  What he is referring to is the 1,000 mile trip to my parents' home, two provinces away.  We've been making this trek every year since before we were married.  This year marks the 15th time we've driven halfway across the country to see my parents, and the 14th time we've travelled all this way with kids.  There have been adventures aplenty since we started:  We've seen moose, bears and foxes,  battled killer mosquitoes while trying to quiet a screaming seven-month old at the side of the road and cleaned up disgusting toddler vomit after eating bad roadside pizza.  We've driven through fog, wind, rain, stifling heat and never-ending summer road construction.  One memorable year Mr. Grant, the dog and I spent a few hours sleeping in the car in a truck-stop parking lot (In the middle of nowhere and me six months pregnant, I might add.)
We've gone from a minivan jammed with playpens and diapers, heating baby food at gas stations, to listening to hours of endless Looney Tunes and SpongeBob DVDs from the back of the van as we crossed the country.
This year it's looking like a pretty quiet trip.  The dog is gone now - this is our second year traveling without Chloe and wherever she is over that Rainbow Bridge, she ain't missing these trips at all.  Offspring #1 is sleeping.  He's 13, so I expect no less.  Offspring #2 has her headset on so she might as well be.  That leaves me and Mr. Grant with three days of no one to talk to but each other.  
Which got me thinking about road trip romance novels.  Believe me, three days in a truck, with no radio stations playing and spotty cell coverage, you do LOTS of that  (along with taking selfies of your shoes and posting them on Instagram, but that's not what we're talking about today.)  
What do I mean by "road trip romances", you ask?  
These are the ones where the hero and heroine are put in the position where they must travel a journey together - and in most cases, it certainly is not because they like each other.  One might be helping the other or they could have a common goal - the basic premise is that they cannot succeed without the other.  So, like cats in a bag they bicker, banter, snipe, scrap, argue, harangue, and end up in a really intimate relationship while they are on their quest.  Then usually something happens after they meet their goal to separate them, then one of them has a EUREKA moment and they ride off into the sunset together.  Oh, and if it's strictly a romance, there will be some earth-shattering nookie happening at some point.
When you think about it (and again, sitting in the truck for hours I had time for this), a road trip romance takes some of the best elements of other tropes, like the ones I call "hate to love", "bicker-banter" and my all-time fave, "marriage of convenience", and throws them all together - with the result having the potential of being absolutely fabulous.  And depending on the genre you are reading, the possibilities are endless:
HISTORICAL:  
Most historical romance readers have read many instances of this storyline - especially in romances set during the Regency.  Men and women couldn't even have their hands naked,  never mind being alone together!  Two protagonists stuck together in a carriage, having to share accommodations?  Simply scandalous!  Explorations of different eras in history will provide a reader with road trips through France, hiding from Napoleon's forces (and if set earlier, avoiding the guillotine), through the English countryside, usually having something to do with Gretna Green, across the wilds of the American Frontier and the wagon trains, chasing the promise of riches in the Klondike Gold Rush,  the harsh terrain and dangerous uprisings in Texas and New Mexico,   behind enemy lines in the Civil War (North or South, I'm not picky!) and my personal favorite, a pirate/privateer ship sailing the blue waters of the Caribbean!  

CONTEMPORARY:  
I'm sure I've read tons of them, but don't remember many straight-up contemporary road trip romances, with the exception of  a novel by Ruthie Knox that had the hero and heroine riding cross-country on bicycles.  It provides a great example of the trope, however:  The heroine needs a partner in order to ride. She answers an ad placed by the Hero's sister to accompany him on the bike trip.  She uses her initials, he thinks she's a man, and his sister doesn't bother to correct him.  They detest each other virtually at first sight, and the game is on.  
PARANORMAL/UF:
Well, this one I don't even have to try.  What you need is a quest, and with all the "fated mates" and parallel worlds, past lives and other funny business going on in these books there isn't a shortage of that.  Someone always needs help - the world as we know it is almost always in danger - and with PNR/UF, authors can be as "out there" as they need to be in order to make their stories work.
ROMANTIC SUSPENSE:  
Again, this is a genre ripe with this type of story.  Sometimes the only question is how much of a role romance actually plays in the plot.  Sometimes the quest itself is more central to the story than the romance
So...Now that we have the genres and the trope itself, what do you need to make a good road trip romance?
I tried to put myself and Mr. Grant into the roles of hero/heroine as I pondered this point, but quickly turned that part of my brain off.  (Note to self: after being married 15 years do NOT attempt to insert yourself and your husband into romance novels.  The result would be closer to an episode of "Everyone Loves Raymond" than a torrid romance. While there is much to be said for having intimate knowledge of the one sharing your sleeping bag, when that one rolls over and squashes you on his way to the bathroom it is more likely to inspire snorts of laughter and an elbow to the gut than it is to inspire butterflies, insta-lust and a passionate interlude.)
HERE’S WHAT I CAME UP WITH:
First:  The characters have to be well-drawn.  Love them, hate them or want to be just like them, we have to care about them enough to follow the journey they've embarked upon.  
Second:  There has to be a good reason for the road trip.  Something compelling, some driving impetus for two characters who would never otherwise meet  be stuck together for the duration.
Third:  The place becomes a character in the story.  Because it does, it must be detailed enough that we learn about where the characters are, without feeling like we are reading a Travelocity ad.
And last, but certainly not least, the hardships.  Yes.  How else do you find the measure of a man, or determine the strength of someone's character, without seeing how they tackle adversity?  A hero who turns his back on the heroine to run away when the wild boar charges, or a heroine who hitches a ride with the first truck that stops and leaves the hero in the dust is not one you'd keep reading about.  
There...Now that you have the whos, the whats and the whys, I challenge you all to find your favorite road trip romance and tell me about it.  If you haven't read one before, by all means try one - it'll be nothing like your own annual family migration, I promise you.