Clause 3, which we are looking at, is dealing with the screening level. At the screening level for alcohol, one typically has the approved screening device at the roadside. With drugs it would be three tests at the roadside for sobriety testing.
What section 256 deals with is the next level up, which is the actual blood sampling in certain cases, narrow cases usually. Or in the case of breath testing, it would be the approved instrument, which is typically administered back at the station. When it's an approved instrument it can be used in court to prove the blood alcohol concentration.