Based on research done prior to making high mount stoplights mandatory in other markets, high mount stoplights (3rd brake lamps) can reduce the occurence of rear end crashes by as much as 54% compared to not having one.

The third brake light is not only easier to see, but the change in the vehicle's 'taillight signature/pattern' makes it easier for the following driver to discern if the vehicle is actually braking.

In Europe, most cars have separate lenses for brakelamps and taillamps specifically because the change in pattern is easier to see. Just look at Volvos, Benzes, BMW's and recent Hyundais (e.g. Tucson) and Suzukis (e.g. APV).