There's a guard rail guy on YouTube who investigates how the guard rails have been fitted. They often have bolts and the tension wire incorrectly installed so much so that they don't even effectively stop small vehicles.
That guy lost a family member to this type of accident and so is on a crusade kinda.
I am contracted to a utility and I get to see just how much time they spend on teaching people about safety. We still see deaths and serious injuries because some people are so lazy they don't give a fuck if they kill someone.
I'm willing to bet the super tall pickups and SUVs are more likely to hop over those steel guardrails, too. Related: Those sloped concrete dividers that have a slightly shallower slope at their wider bottom? Those are super effective, because that bottom slope deflects the vehicle's front wheel, causing it to turn slightly away from the barrier instead of continuing to smash through it.
They have other issues though. They cost more to produce, cost more to install and cost more to maintain. They also accumulate snow, which would otherwise blow through an open W guard rail.
A third option are wire guards. They're cheaper on all accounts, don't get tagged with graffiti and statistically save more lifes. They work best on long straight stretches, but because of the flexibility, they are not ideal for inner city streets where it's best to avoid any lane breaches at all.
That's a myth. It may look like a "cheese grater" but statistics show that they have saved more motorcycle lifes than any other barriers, and there are no records of anyone actually getting grated.
I hate to be the "sources" guy, but the last time I looked at what few studies there where on the topic they weren't positive. Could you direct me to where you found that info?