Huh? Most bus stops have a map showing the code for each bus stops. Cardiff bus also have a website which shows the routes and times and if you're near a Cardiff bus you can use the free WiFi to access the website.
More people should use public transport to save us from the congestion which is building up, but the argument against would be over-crowding and the bus or train never being on time (whether that's early or late so you have no hope of guessing) rather than being hard to work out.