Emergency braking system activated for no apparent reason. Traveling at freeway speeds on a straight section of freeway when braking system briefly activated. There were no other vehicles or obstructions within 200yrds that might have triggered this. Had someone else been driving or if we had been in rain or snow conditions the outcome might have been different. Vehicle was approx 3 days old when this happened and brought back to the dealer to check. They could not reproduce. There were no prior symptoms or warning lamps