time, occasion, take journey
趟 centers on a measured movement or occurrence: a time or occasion, and by extension a journey taken. The meanings connect through the idea of a counted trip or instance.
趟 combines 走 (run, move) with 尚, which likely contributes a phonetic element. The character originally referred to a leap or a bound, and later extended to a trip or an occasion. The exact historical development of the inner component is uncertain.
The running radical 走 suggests movement, and the inner 尚 looks like a small roof over a mouth, as if counting stops on a journey. Picture running from one shelter to the next, each stop marking a time or occasion on your trip.
For トウ, imagine taking a journey to a tall tower: tower -> トウ, and each step of the trip is a counted occasion.