Final answer:
Leaving a truck unattended without applying parking brakes or chocking the wheels is never safe, as regulations require these safety measures to prevent accidents.
Step-by-step explanation:
The question relates specifically to safety protocols for trucks. There is no demonstrated safe scenario in which you can leave your truck unattended without first applying the parking brakes or chocking the wheels. The information provided suggests that the context for this question may be about understanding stopping distances and the safety measures involved in preventing a truck from moving when unattended. However, safety regulations typically mandate that the parking brakes should be applied, and the wheels chocked if necessary, to ensure the truck does not move and cause an accident. Many factors would affect actual stopping distances, such as the weight of the truck, road conditions, and brake effectiveness, but all are moot if the truck is unattended, as the vehicle should be secured regardless.