Hitting the height barrier is likely to be less harmful to the driver and other people than hitting the bridge itself, so that seems to be taking due care (and

Hitting the height barrier is likely to be less harmful to the driver and other people than hitting the bridge itself, so that seems to be taking due care (and again, killing the driver is extremely unlikely in either scenario). The purpose of a height barrier is to act as a sacrificial component and I would consider that it improves the safety of the structure as well as being cheaper. It's a very common design to see metal or concrete poles (bollards) used to prevent drivers from causing harm to other road users, features or shop fronts. They're safe and effective.