This script plots two ATR (Average True Range) values, one based on only bullish and the other based on only bearish bars. If the current bar is positive, the negative ATR will use its last known negative bar for the calculation. You can smooth bar directions by using the Heikin Ashi setting.
Use this the same way how you would use the regular ATR indicator, but with the added value of knowing which side of the market has more volatility.