No Backseat Boozing
Applicable States: The 39 states in compliance with TEA-21
States that follow TEA-21 agree to six standards, which prohibit the driver and all passengers from consuming and/or possessing any alcoholic beverages while in a vehicle. In other words, even if you haven't taken a sip, you can end up footing some serious fines.
No, your state isn't just trying to make your life difficult. States in compliance with TEA-21 are awarded extra funding for highway and road building. This hefty incentive is likely why most states opt to follow the proposed law.