[dave333]

That is a good way to have an accident - I know since I've done it. While "looking one way" on a USA counterclockwise roundabout you are looking left to see traffic already on the roundabout and if clear you go and run smack into the back of the vehicle ahead of you who for some reason stalled or hesitated or just judged the traffic differently. However it will be a low speed accident.

[sierra1011]

As a general rule, one should be looking in the direction in which the vehicle is traveling. It's easily done though, if rushing, or if the vehicle in front pulls away slightly but stops again.