You are doing the right things by shadowing some practicing engineers. One positive thing is that most engineering fields share the same set of core classes in college, so the first two years of any engineering program will be close to the same, no matter which discipline you want to pursue.
One thing I did was once I got into college, I made appointments with all the heads of the different engineering departments that I was interested in. This included Civil, Industrial, Mechanical and Electrical Engineering department heads. In my experience, most of the heads of the departments will have some ‘real life’ work experience, and my main two questions for them was, ‘Why did you choose this field?’ and ‘Why are you still excited to work in this field?’
Seeing as how you enjoy the psychology side of things already, I would guess that any job that involves human interaction, negotiating and navigating the relationship side of business is going to interest you. This can be found in any engineering field.
Each engineering discipline has unique characteristics that set it apart from the others. Civil engineering (traffic engineering falls under this) usually involves some type of creation/construction. Whether it’s buildings, bridges, or traffic signal patterns, civil engineering puts things together. Industrial engineering is process flow and improvement. This could involve anything from hospitals (think about how items move from supply room to operating room) to package flow (think UPS and FedEx). Mechanical engineering is more hands on, and involves making things work independently. Think elevators to airplane engines.
The best advice I can give you is to continue to seek people out who can share with you the pieces of their job they enjoy and don’t enjoy. Ask why they picked their profession/engineering discipline and see if any of their answers create an excitement in you.
Good luck with your senior year, and keep looking towards the future!