The squeeze takes advantage of quiet periods in the market when the volatility has decreased significantly and the market is building up energy for its next major move higher or lower. Period of low volatility are identified as the times when the bands "move closer together". How do we know that the current narrowness is really narrow enough to qualify as low volatility? By adding Keltner Channels and momentum index oscillator as per mentioned in John Carter's book Mastering the Trade.

While Bollinger Bands expand and contract as the markets alter between periods of high and low volatility, the Keltner Channels stay in more of a steady range. The momentum index oscillator is used to estimate the direction.

How does this Setup work?
The quite period is identified whent he Bollinger Bands narrow in width to the point that they are actually trading inside of the Keltner Channels. This marks a period of reduced volatility and signals that the market is taking a significant breather, building up steam for its next move. The trade signal occurs when the Bollinger Bands then move back outside the Keltner Channels. Use 12 period momentum index oscillator to determine whether to go long or short. If the oscillator is above 0 when this happens, GO LONG; if it id below 0 then GO SHORT.

Usually the moves are explosive when the BB Width is lowest over past 6 months which comes to across 126 days and hence we need more than 126 price data bars. Also choose BBWidth < 0.05 for better results in the strategy for daily data. I have included Trailing Stop and Stop Loss as variables so you can easily backtest as well as use optimizer....