It&#x27;s called filtered permeability, and is a common retrofit in some countries in Europe. Wealth doesn&#x27;t come into it — you will find it in some really poor parts of London, as well as the City (financial district) and some very rich neighbourhoods.<p>The point is that the non-arterial road can&#x27;t handle the load, so the barrier returns it to its original purpose — the residents of and visitors to that street.<p>The intention is that the people who were using this route either
- use the main road (slightly increasing the traffic there)
- use public transport or a bicycle instead
- stop making the journey altogether<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Permeability_(spatial_and_transport_planning)" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Permeability_(spatial_and_tran...</a>