The Principal Act is hereby amended by the substitution for section 46 of the following section.

"Special speed limits.

46.

(1)

(a) The council of a county or the corporation of a county borough may make bye-laws specifying in respect of any specified public road or of all public roads within its administrative county the speed (which shall be known as 'a special speed limit') which shall be the speed limit on such road or roads for mechanically propelled vehicles.

(b) The corporation of a county borough may, in bye-laws under this section, provide that the built-up area speed limit shall not apply to any specified public road in its administrative county by declaring the said public road not to be a public road in a built-up area for the purposes of section 45 of this Act.

(c) The council of a county may, in bye-laws under this section -

(i) provide that the built-up area speed limit shall not apply to any specified public road which is in a borough, an urban district or a town within its administrative county by declaring the said public road not to be a public road in a built-up area for the purposes of section 45 of this Act, and