I think statistically the number of deaths in work zones has been decreasing the last ten years, but they just want it to decrease faster.

I think it's something like 40x as many construction workers die outside of posted work zones than inside posted work zones, so I think part of it is money related. If they really wanted to reduce fatalities, they would police unmarked work zones.

source: http://www.workzonesafety.org/crash_data/