I would say the single most important factor is the DRIVERS (plural). The problem is you only have control over one of the drivers in a potential collision. Having a car that can safely maneuver so as to avoid the collision is quite important indeed. The January 12, 2004 New Yorker has a great article about the myths of SUV safety called "Big and Bad". The author describes the difference between "passive safety" (ability to take a hit without being killed) versus "active safety" (ability to outmaneuver a collision so you don't get hit). SUVs have a lot of passive safety, but are not as maneuverable so they can't avoid collisions like a smaller car like a VW Jetta. This makes the Jetta safer on average if I recall the article accurately.
If you don't want to pay for the whole article, there's a Q&A with the author which covers a lot of the material.
True, we would be a lot better off if all drivers were sufficiently aware of their surroundings, but the fact remains there is a lot that can be done to avoid most accidents if you are an aware driver. Anecdotally, all the multi-vehicle accidents I've witnessed, happened because both drivers made a mistake or failed to take evasive/defensive action. I've seen drivers accelarate from the green, and get T-boned because they didn't look left and right before proceeding through the intersection. How stupid are people to proceed through an intersection without looking left and right? They ASSume the other driver will stop. I always look whether I'm the first driver or the last driver in line.
Also, who watches their rear view mirror when slowing for a stop or while stopped at a traffic light? I do. If I see an approaching vehicle that does not appear to slowing down 'fast enough', I will pump my brake pedal (or lever) to flash the brake lights or even temporarily turn on my four-ways to get their attention while they type their latest text message.
Many of my accident avoidance habits and skills were honed from 35 years and well over 100,000 miles logged on a half-dozen or so motorcycles. My life depends upon my ability to predict and be prepared to react to all kinds of bone-headed actions by other drivers on the road. And as a motorcyclist, I've seen it all. There are times when I swear, a driver looks me in the eye, and yet still pulls right out in front of me. (I look for eye contact to 'confirm' whether another driver 'sees' me).
Reading people's head and eye movements, watching the front wheel, not the car to read a lane change, lane positioning, positioning relative to other vehicles, maintaining total situational awareness and so on. Watching the road five to ten seconds ahead to maximize reaction times and so forth. Too many things to address in this format.
As a motorcyclist, I practice the sport. That means I find a remote section of lightly traveled roadway and I will periodically practice 'panic' stops. I know what it feels like to have the front tire howling at the point of lock-up. I will practice evasive maneuvers around an imaginary object in the road. Back in the early nineties, I attended Keith Code's Superbike school. I will admit, the small size of a motorcycle has permitted me to avoid more than one accident. I also drive a Suburban, F-150, a 38 ft RV, as well as a Jetta. :-)
I like your part about looking ahead. I start slowing down when the 4th or 5th guy ahead of me starts applying the brakes. This usually gets the guy behind me to slow down or go flying by me on his way to his next accident or close call.