MOST Law Enforcement Agencies consider erratic drivers to be "Life Threatening Emergencies"
and therefore proper to be reported on a 9-1-1 line - and they WILL attempt to
intercept and further observe the erratic driver.

And DON'T try to "follow" a high-speed vehicle or worry about the License Number -
the more important reporting issues are exactly WHERE you are (location)
and the Direction the erratic driver is heading; a good description of the erratic vehicle
is helpful - but not exactly required - they'll be looking for ANY vehicle acting strangely near
the area you've alerted them to.

Another "advantage" of calling 9-1-1 is that 9-1-1 centers have good communication with
adjacent communities - and can frequently alert multiple departments to be on the lookout for
the erratic driver - you get more bang for ONE phone call!