I just returned from trip #11 since 10/2004, and have driven in the DR each time.
One thing is for sure: do NOT drive there if you want to drive like you do in Suburbia USA. No way. It is NOT for the polite, safe drivers from middle America, where everyone follows the rules, gosh darn it...
You have to drive somewhat like a Dominican, but not the crazy Dominicans (like the ones that, while you're patiently waiting to make a left turn in traffic, will pass on your right, turn in front of you to make THEIR left turn ahead of YOU.
"Defensive driving" takes a whole new dimension in the DR. Traffic rules really don't apply, and certainly not enforced. 3 lanes of traffic? No prob! Just stack cars 5 lanes across. A car length for each 10mph for proper safe spacing? Just means room for more cars and motos to cut in front of you. Hi-beams in your eyes at night? That's a symbol of politeness. You absolutely, positively need to have your head on a swivel every second you are behind the wheel of a vehicle there, Big Time. Driniking and driving in the DR? Totally irresponsible and moronic, much more so than about anywhere else in the world. My friend tried that stunt in the mountain road between PoP and Santiago, and ended up in a ditch in the middle of nowhere...and had to be towed to the airport police station in STI, with $RD12,000 damage: detached plastic body panels, busted fenders, and broken transaxle linkage. Not a good vacation thing.
The traffic patterns there actually ~work~. You just have to adopt the proper Dominican Driving Zen to *feel* it, like corpusles in an artery.
I'm more concerned of getting screwed by the rental car company there than being at fault in a bad accident there. I've had suspension failures from potholes, busted windshields by rocks, flat tires, failed water pumps, headlights busted by rocks, etc., etc., etc. I fixed the windshield myself cheaper than the rental company would have charged me.
One caution: in the DR, while driving, PAY ATTENTION AND DRIVE!!! No sight seeing. My friends and I usually alternate driving so we can enjoy the sights while NOT driving. Getting distracted can be hazardous.
Enjoy driving in the DR. Just forget about everything you were taught in Drivers Ed.