Carrying a heavy load is a clear sign of fatigue. The dreamer feels physically, mentally, or emotionally overwhelmed. Your unconscious is warning that you need to rest.
Gallery of dreams
Body reactions during sleep
Most of us must have experienced hallucinations or night mares. When we experience such dreams we are unable to move or react. This stage is referred to as sleep paralysis. This type of dream occurs in between wakefulness and REM. As it occurs during the REM stage, it causes complete muscle weakness preventing the individual reacting to the dreams.
One of the reasons why people always get involved in road accidents is that, they are tired while driving, or that they lack sleep. Many people do not realize that their performance can be highly affected by having not enough sleep. Sleep deprivation can affect reaction as well as decision making, not to mention that it could make a person unable to drive well. It goes the same with drunk driving.