[gcruse]

How would you effectivly test for DUI/DWI for pot?
 Roadsides are not accurate enough alone.

If you're not sufficiently impaired to be roadside
tested, that you aren't really DUI, are you?

[longtermmemmory]

They are legally not even tests they are exercises. In fact the HGN is generally not allowed in trial because it is so inacurate and undependable.

The roadsides have a 40% falure rate in sober people. Would you get on an airplane if 40% of the passengers were going to die?

In trial roadsides are only a minor challenge. I advise people to always refuse EVERYTHING. There may be a 1 year administrative suspension but that can be disputed in an administrative hearing. (again if you know the system not so hard)