Here the county has placed concrete barrier sections on a bridge in order to make it one lane. Since they are heavy, I would assume this is not done to keep two vehicles from being on the bridge at the same time for weight reasons.
Looks like they were trying to make it safer because it was too narrow, but this is anything but safe.
https://www.google.com/maps/@34.6464066,-96.5001754,3a,72.9y,301.81h,80.08t/data=!3m6!1e1!3m4!1sGU0vn03XZvhYBdKXIGgKpQ!2e0!7i13312!8i6656 (https://www.google.com/maps/@34.6464066,-96.5001754,3a,72.9y,301.81h,80.08t/data=!3m6!1e1!3m4!1sGU0vn03XZvhYBdKXIGgKpQ!2e0!7i13312!8i6656)
I'm thinking they're there because the existing safety barriers aren't safe enough.
But, yeah, the jersey barriers should be adjoining each other, not separated like this. And the end ones should have some sort of impact or deflection equipment leading up to them.
And the money to build it was.... And for no benefit except to appease the insurance companies.
Doesn't look like it was wide enough for two vehicles anyways.