positional transits of critical houses

Hell Ernst, when you explain for example venus transiting the 4th house am i checking the bhava house and cusp of the 4th in the rasi chart and the D16 for vehicles. For example i have aquarius as 4th house in the rasi and scorpio as 4th bhava cusp in d16 when venus hits the 4th cusp which varga am i looking at to activate vehicle issues rasi or D16 and does venus have to be retrograde in that bhava? to be significant.