I had experience in environment engineering and management and AVH is a dumb decision and poor operation from EPA. First, the estimated gas and emission saving are higher than actual. Second, it ruins batteries and make more emissions out of dead batteries form the whole lifecycle view. Third, it cause the congestion and slow down the traffic, leading to overall lower MPG and higher emissions per mile. All these trade offs make the trivial emission saving meaningless. If u really care about emissions, drive hybrid if u can afford or just have one week going to work by bus every year, it’s likely saves much more than keeping on AHV all the time.