<prompt> Translate the following text to EnglishKwa kuongezea, wiani wa posta wa juu hupunguza athari za kiasi kwenye gharama za kitengo cha utoaji wa mitaani, na kiasi cha juu hupunguza athari za wiani wa posta.  <response>: Furthermore, high postal densities reduce the impact of volume on unit street delivery costs, and high volume reduces the impact of postal density. 