Improving truck-exterior safety standards: deformable impact points, robot drivers. Combine that with environmental improvements - fewer places to get squished between a truck and arbitrary railings, say. And add medical improvements to the point where you'd have to splat a brain to get a sure kill. Safety standards that require a Culture-style life-support collar on all trucks.

All engineering. It's not good against infinite time, but it ought to make traffic fatalities rare and remarkable.