One of the things about evaluating the cost-effectiveness of a safety feature is that there's implicitly a monetary value assigned to human life, when you know the probability of something saving a life and the amount of money that thing costs.
https://www.transportation.gov/office-policy/transportation-...
For 2022, the US Department of Transportation benchmarks that at $12.5 million and that's the number used to decide if something is cost-effective.
If one is proposing that society spends more on road-safety, that's more or less saying that $12.5 million should be higher. So what should it be? Are we ok with spending $20 million? $50 million? $100 million? Because that's the question we're implicitly answering when we decide if a proposal such as bollards are cost-effective.