"When I was travelling in Amercian" Dang people can travel in different languages? Man that would be interesting to try.

car pool lane only (on a freeway)

This refers to multiple people travelling in one car... they also will say "High Occupancy Vehicles only" (or HOV). during periods of heavy traffic, they restrict certain lanes to these cars. the term "car pool" specifically means multiple people traveling to one location (usually work or the office) in one car. for example, instead of driving to work in the morning, you would wait for your co-worker to pick you up and then you both would drive to the office.

共行車道

A car pool generally means a system where people who make similar trips to share a car for that trip. For instance, if you have people in your neighborhood who go work in the same company or same area as you, you might share one car to go to work. Car pool lanes are lanes where you usually are required to have more than 1 person in the vehicle in order to drive in it. Sometimes the restrictions might be a little different. This system is meant to encourage car pooling to save resources by offering car poolers their own lane and supposedly better traffic conditions. Personally, I think cleaner and more reliable public transportation systems would be better.