While traveling at night on a 4 lane highway at 70 mph in heavy traffic the vehicle went into limp mode without warning or any symptoms of a power problem. we had to move across four lanes of car and truck traffic while rapidly decelerating. luck and skill prevailed to avoid a serious and potentially fatal accident. no warning indicators were displayed. safely in the breakdown lane the vehicle continued an approximately 1300 rpm idle and would move at about 15- 20mph. i stopped the vehicle and the acclerator pedal continued to be unresponsive. i placed the vehicle in neutral with no change in the ability to increase rpm with the accelerator. i shifted back to drive and normal acceleration function returned. we drove another 35-40 minutes without further problems. the next morning the vehicle drove normally and i took it to the vw dealer. their diagnostic review showed no issues and no malfunctions were detected.