A planetary gear train may include an input shaft, an output gear, a compound planetary gear set including a first and second sun gears, a common planet carrier, and a common ring gear, a third planetary gear set including a third sun gear, a third planet carrier, and a third ring gear, a first rotational member consisting of the second sun gear, a second rotational member consisting of the common planet carrier selectively connected to the input shaft, a third rotational member consisting of the common ring gear connected to the output gear, a fourth rotational member consisting of the first sun gear, a fifth rotational member consisting of the third ring gear connected to the input shaft, a sixth rotational member consisting of the third planet carrier, a seventh rotational member consisting of the third sun gear operated as a selective fixed element, and friction members.