I guess because the intention wasn't to close the road, but to prevent through traffic and the use of residential streets as rat runs.
The problem with permanent barriers is that they don't just block rat runners, but local residents, buses, emergency vehicles — and anyone else you want to exempt, like visitors, carers, school minibuses, delivery vans, council vehicles (!), taxis etc.
Gates / openable barriers wouldn't be much better — apart from the poor optics of creating gated enclaves, they can break at the wrong times.
I'd have thought the main issue is privacy with the ARPN cameras, but perhaps that horse has already bolted with the huge number of them in London already.
Ed Saper ● 2046d