A system and method for reducing transmission collisions. In one embodiment, a transmitter for communicating of a smart grid power line network includes an arbiter. The arbiter is configured to select a transmission interval during which the transmitter can transmit. The interval is selected from a plurality of available transmission intervals reserved for contending transmissions, and selected based on a level of a hierarchical network at which the transmitter is located. The interval selected is different from any interval used by a different transmitter spaced two hierarchical levels away from the level of the hierarchical network at which the transmitter is located.