This is a program for the city of Denver. Driving speeds should never approach what they would be in a rural area. Even if a deer ran out onto Federal, no one should be going fast enough for someone to be killed. I believe 100% that we can have zero traffic fatalities in the city of Denver. 

The challenges are greater on rural roads, like the deer collision you mention. That's an environment where speeds are going to be high, and so are the consequences. 
There are still strategies that can help in those areas too. Wildlife crossings, cable rails, occupant protection, slower speeds, better driver training and licensing. I think getting to zero in rural areas is more difficult, but should still be the goal. Sweden, where the concept of Vision Zero originated, has a traffic fatality rate one fifth of what the United States has. They have a lot of rural roads.