NEC ECC: Where would the compiler specify the Method of Measurement?

In an ECC Form of Contract where would the compiler specify the Method of Measurement for the proposed Works?

I refer specifically to highway works for Local Authorities.

Here, there is an option to use a generic CESMM4 type measurement or a more bespoke Method of Measurement for Highway Works from the Manual of Contract Documents for Highway Works.

I've seen a small number of attempts to clarify this issue in Contracts (e.g. Z-Clause and Works information) but largely my experience is that contracts are silent on the issue.

I welcome any clarification you could suggest.