Access to public highway

Has anyone seen any guidance on what this will mean if it stays in the Housing & Planning bill? Does it meant the site has to adjoin adopted highway or just that it is possible to drive from the plot to highway? I have several sites intended for serviced plots which will have access to highway via a private road which will be owned by the buyers of the plots. Bringing the roads up to adoptable standard would make the cost of providing the plots too high and in one case is not possible due to the gradient and width.