And because of the hospital testing in proposed section 256. It was felt when that amendment was made—I believe it was 1999, after the committee had reviewed all the impaired driving provisions—that the four hours was used for blood sampling. Typically there would be an accident involved, and they wanted to ensure that the police could still make the demand in the time period.
Here what is being suggested is that with the screening level demand, the police should be able to look back three hours to the person's driving.