Dreams involving vehicles, such as trucks, often symbolize your journey through life and the direction you're taking. The act of the truck hitting a tree could represent a sudden disruption or obstacle in your path, suggesting that you may be facing challenges or unexpected events in your waking life.

Stopping to call 911 indicates a sense of responsibility and concern for others, showcasing your instinct to help in times of crisis. However, noticing that others are already helping may suggest feelings of relief or a realization that you are not alone in facing challenges; there are people around you who are supportive.

Overall, this dream may reflect your awareness of difficulties in your life and your desire to assist others, as well as a recognition that help is available when needed. It could be beneficial to reflect on areas in your life where you may feel overwhelmed and consider reaching out for support from those around you.