You do not remove them. But you should change them when environment changes. Straw bale was decent indicator back in the day. But I think there should be some more modern and even global standard that law could be changed to. And this should be done with reasonable planning, schedule and communication.

Decent indicator of what?

It could be, to the contrary, that the legislators have come up with "straw bale" as something that simply does not belong under the bridge, in order to raise the brows of the people navigating the river, and make them wonder what's going on, all that in order to draw their attention. If so, it serves its purpose even more as straw bales are getting less common.