This is a pretty straight forward trade. The daily Transportation Index ETF IYT jumped from $173 to $187 in three days, which makes it overbought for a swing-trade short. Then, its major trend-line price hit on Thursday, stretching all the way back to 2015 as multiple technical indicators screamed 'overbought.'
Finally, add in that this run is factoring in tax reform, which means there will be little further risk, even if tax reform gets through (which is likely). This is a solid risk/reward swing-trade short. I would like to see a pull back minimally to $168.