He went on a business trip together with his colleague.
Tips
usage
一道 means the same as 一起 (yīqǐ, together) but is slightly more literary/formal. It's common in written Chinese and formal speech. In casual conversation, 一起 is more natural.
usage
Note: 一道 can also be a measure word for dishes, barriers, or questions: 一道菜 (a dish), 一道题 (a question/problem), 一道门 (a door/gate).
