Unwaith y dynodir ardal yn fan tawel, bydd yn ofynnol i bolisïau cynlluniau datblygu ystyried yr angen i amddiffyn y man tawel rhag unrhyw gynnydd mewn sŵn a rhoi ystyriaeth arbennig i effeithiau unrhyw ddatblygiad cyfagos a allai achosi sŵn.
Once an area has been designated as a quiet area, Planning Policy Wales requires development plan policies to have regard to the need to protect it from an increase in noise, and requires special consideration where noise-generating development is proposed nearby.