While the car is in motion with cruise control active, pressing the "set/-" switch is supposed to decrease the vehicle speed in 1 mph increments for each press of the switch. when attempting to decrease speed gradually for upcoming speed limit changes, or when vehicles pull-in a bit too soon after passing, my tiguan will often quickly increase the "set" speed by by 2-4 mph when the "set/-" switch is pressed. an internet search shows that other vw owners have experienced this same phenomena and the dealers tell them it is not a safety concern! i disagree with that statement. it's true that the cruise control can be cancelled or turned off in these situations. that's called a "work around." in other words, there's a defect, but as long as you know how it will act, be prepared and cancel rather than use the "decelerate" switch. volkswagen needs to address this, as most people would be expecting the car to slow when this switch is pressed, not quickly accelerate.