They including a road widening as 'street safety'. Very generous interpretation of the term.
If it feels like your car is not squeezed, the natural inclination is to drive faster. You need to resist that inclination to stay within the speed limit. Basically, increasing the perceived width of the lane you’re in increases speed, and speed of crash is one of the core determinants of crash fatality.
And your assumption that higher speeds are unsafe is unfounded- unless you want to eliminate cars altogether (“there is no safe sex/speed”), a given roadway has a generally safe speed and typically this would be calculated and considered in the widening of the shoulders
Calculations and considerations are all well and good, but when the rubber hits the road, wide straight roads will lead people to reason that it's fine to drive fast. I'd much, much rather have people think it's a pain to take my road because it's too skinny than to have 50-60 mph traffic accidentally kill my son or my neighbors when they choose to go outside.
If you want to do something about it you can lobby for a traffic study
I mean, you have to strike an object. Adding obstacles on the shoulder seems like it would increase that likelihood. It would also prevent the option to avoid oncoming traffic, or a sudden braking vehicle in front. I have seen both of those happen multiple times.