Texas has seatbelt and child safety seat laws that apply to passengers riding inside vehicles but also has laws pertaining to passengers outside of the vehicle interior. This article explains when a passenger or pet can ride in the bed of a Texas pickup truck and the penalties for a violation.
Texas requires all interior passengers—children and adults—to be properly restrained by a seatbelt or an appropriate child harness. Passengers under the age of 18 are also prohibited from riding in an open truck bed, open flatbed truck, or an open flatbed trailer. Exceptions to this rule exist for parades, driving on the beach, permitted hayrides, and some farm-work.
A violation of the restrictions for passengers riding outside the interior of a vehicle is a misdemeanor and carries a fine of $25 to $200 for the driver.
An accident with a truck-bed passenger can result in serious injury, civil liability, and increased insurance costs. However, a criminal citation can't be used in court to prove negligence.
While restrictions exist for human passengers in the bed of a pickup truck, Texas does not prohibit animals from riding in truck beds. But you may want to look into local rules as some cities, like Dallas, criminalize the unsecured transportation of animals. In any case, the American Veterinary Medical Association recommends that pets be secured either by a kennel in the truck bed or by a harness inside the cab.