This article breaks down the naming convention NDDOT used for Route ID fields in Numetric.
Route Type
I = Interstate
L = Local
P = Private
S = State
T = Trail
U = US Highways
Route Number
A sequential number generated from ArcMap.
Direction
N = North
S = South
E = East
W = West
_ = Underscore is used for Local roads because they do not have direction in their name.
County FIPS
County roads will include the County FIPS number. This is not used on State Highways; instead 000 is used to indicate State Highways.
Route Qualifier
A = Alternate
B = Business
M = Mainline
R = Ramps
Route Sequential
Route_Seq is assigned on state business routes and is not used on local and county roads.