I'm, on balance, in favour of barriers.
They regularly get crumpled and hopefully are doing their job of bringing drunk/mad/asleep drivers to a safe stop, without killing anyone.
They stop parking on the pavement too.

But perhaps pedestrians(/cyclists) are getting caught on the wrong side and getting crushed as they have no-where to go.

I'm sure tfl have done loads of research ..... then picked the cheapest option.