The Turbo measures 16.5 inches wide, the Parkway 17 inches wide...BUT the Turbo's armrests actually make it more difficult to buckle next to another carseat, especially in three-across situations. The Parkway is about the most perfect booster for three-across/tight spots because there are no armrests to get in the way of buckling. We had the Turbo next to a harnessed seat in the middle of my two-seater middle bench (minivan) for awhile and it was horrible to get your hand underneath the armrest to buckle the seat. The Parkway is now in that spot and it's much easier.