drivers do not have a legal duty to ensure that their intoxicated
passengers are seat belted:
We find nothing . . . to support the proposition that, as against a plaintiff
passenger, an intoxicated driver is less entitled to rely on a seat belt defense
than is a sober driver. Because he is held to an adult standard of care when
entrusted with an automobile, Bonds [the plaintiff passenger] should have
known his voluntary inebriation would diminish his appreciation for automo-
bile safety measures including the use of a seat belt. Our holding that Fleming
was not under a duty to fasten Bonds’s seat belt is consistent with the public
policy expressed within Florida’s Safety Belt Law, section 316.614, Florida
Statutes (1988). Enacted after this suit was initiated and thus technically
inapplicable, the statute, nonetheless, requires front seat passengers over
16 years of age to buckle up, but the driver is not accountable nor negligent if
the passenger fails to do so. See § 316.614(5), (10). It must be remembered
that the seat belt defense goes only to the issue of damages, not liability for
 Similarly, in Collins v. Thomas, 182 Vt. 250, 938 A.2d 1208
(2007), at paras. 14-19, the Supreme Court of Vermont disagreed
with the plaintiff’s argument that the driver had failed to exercise
reasonable care after volunteering to drive the intoxicated plaintiff because he failed to secure the plaintiff’s safety “either by
having him sit in the cab wearing a seatbelt, or, at least, by stopping the truck after realizing that he was in a precarious position
in the bed of the vehicle”.
 This issue appears to have first been dealt with by the
Australian courts in Lerga v. Susa,  ACTSC 105, where the
intoxicated passenger, not wearing his seat belt, died in a MVA.
The court discussed the negligence of a driver’s duty [at paras.
39, 43, 48, 49 and 85]:
As to the first consideration, the answer would very much depend, in the
circumstances of this case, on whether the deceased was too drunk to have
operated the seat belt. The driver may have contributed to the lack of use of
the seat belt by his passenger by failing to ensure the seat belt was done up.
The extent of that failure might well have been affected by the driver’s rela-
. . . . .
In the present case, a prudent driver, knowing his or her passenger to be
intoxicated, would have an enhanced duty to ensure that the passenger was
safely positioned in the vehicle. That would include the proper engagement of
the seat belt. It would be no excuse for the driver to claim that he or she was
too intoxicated to carry out that duty.
. . . . .