Exits where the majority of traffic exits off the highway.

[webny99]

Confirmed.  The exit ramp has a higher AADT than the segment of I-15 north of that junction.

[img snipped]

It makes it really simple and easy when that's the case. However, it's not necessarily a pre-requisite. It could still qualify even if I-15 north of that junction had volumes higher than 8,100 if the volume of entering traffic was greater than the difference.

[ftballfan]

One I travel through a lot (unsigned I-296 provides access from NB US-131 to I-96 in either direction and from EB I-96 to SB US-131)
US-131 south of unsigned I-296: 115,081
US-131 between unsigned I-296 and I-96: 52,768
US-131 north of I-96: 73,503
Unsigned I-296 combined: 62,313

Another one in Michigan:
US-10 east of M-115: 7,225
US-10 west of M-115: 4,248
Ramp from WB US-10 to WB M-115: 2,680
Ramp from EB M-115 to EB US-10: 2,754
M-115 west of US-10: 7,126
M-115 east of US-10: 5,625

Non-freeway example (a borderline one as well)
M-45 east of M-231: 12,094
M-45 west of M-231: 6,451
M-231 north of M-45: 8,626

[kphoger]

Confirmed.  The exit ramp has a higher AADT than the segment of I-15 north of that junction.

[img snipped]

It makes it really simple and easy when that's the case. However, it's not necessarily a pre-requisite. It could still qualify even if I-15 north of that junction had volumes higher than 8,100 if the volume of entering traffic was greater than the difference.

Right.  Unfortunately, the AADT map considered it all one segment north of the exit, therefore there's only one data point.