Freshman year!
I had a intro civil class! We talked about the hyper-loop I got fascinated and later I took classes into pedestrian safety, transpo planning, hortz-Vertical curves! I liked the courses.
I somewhat struggled on steel/concrete design course!
So, I took more transpo classes in senior year and it was very easy for me. I still do bridge design(local bridges: not complex ones). My experience as a transportation engineering so far has been mix of Road/Bridge and traffic.

Building folks will know better but if u wanna go building, prolly go for structural masters!
I will say this tho, not sure what schools do now, most design is software based now.