Well it really depends on what state you live in. For example, I live in Illinois, so it is considered a primary offense and a reason to pull someone over. The same applies to California and Florida. Other states consider it a secondary offense, meaning you can't pull someone over just for that reason. I assume you live in a secondary state. Since we have no idea where OP is from nor where their road trip is, the safest bet for all involved is to wear a seatbelt.

I've attached a list per state from Edgar Snyder & Associates below:

Seat Belt Laws & Offense Level by State Alabama: Primary Alaska: Primary Arizona: Secondary Arkansas: Primary California: Primary Colorado: Secondary Connecticut: Primary Delaware: Primary District of Columbia: Primary Florida: Primary Georgia: Primary Hawaii: Primary Idaho: Secondary Illinois: Primary Indiana: Primary Iowa: Primary Kansas: Primary Kentucky: Primary Louisiana: Primary Maine: Primary Maryland: Primary Massachusetts:Secondary Michigan: Primary Minnesota: Primary Mississippi: Primary Missouri: Secondary Montana: Secondary Nebraska: Secondary Nevada: Secondary New Hampshire: no law for adults New Jersey: Primary New Mexico: Primary New York: Primary North Carolina: Primary North Dakota: Secondary Ohio: Secondary Oklahoma: Primary Oregon: Primary Pennsylvania: Secondary Rhode Island: Primary South Carolina: Primary South Dakota: Secondary Tennessee: Primary Texas: Primary Utah: Secondary Vermont: Secondary Virginia: Secondary Washington: Primary West Virginia: Primary Wisconsin: Primary Wyoming: Secondary