"The DOT said long-acting edibles could increase impaired driving in Hawaii"

THC is THC and the duration of its effects has nothing to do with the means of ingestion.  It takes considerably longer to feel the effects when swallowed as compared with inhaled, but that has no bearing on duration.  I think the issue has to do with dosage, since the quick results from inhaling it allow users to "titrate" their alteration of consciousness more accurately.  

There's no effective way to do that when THC is swallowed, so it's possible to ingest too high a dose and then the user is "along for the ride".  So the bottom line is to make sure there's good quality control on edibles as well as a reliable indication of the dosage contained in each item.

Driving impaired is something that should never be done, no matter what the driver has "on board".  But the means of ingestion really has nothing to do with that.