The rules of polo can best be described as traffic rules. Starting with the first throw-in, the path the ball takes creates a right of way which determines the direction and path which the players may take in order to get to the ball. A player following the line of the ball has the right to hit the ball on the offside (or right side) of his horse. This is his right of way. As on a highway, an opposing player may not enter the right of way in a manner which would cause the player with the right of way to slow down or, worse, risk a collision. To the players and umpires, this is all a matter of judgement or opinion, and in many cases, the opinions differ significantly.