▁end ▁of ▁the ▁tra iler ▁or ▁vehicles ▁that ▁may ▁be ▁present ▁in ▁the ▁next ▁l ane ▁( because ▁the ▁load ▁ob struct s ▁the ▁mirror s ), ▁the ▁general ▁procedure ▁is ▁as ▁follows : ▁The ▁tr uck ▁driver ▁sees ▁an ▁obst acle ▁and ▁signals ▁with ▁his ▁left ▁( or ▁right , ▁if ▁in ▁a ▁left - side ▁traffic ▁country ) ▁turn ▁signal ▁( aka ▁" bl ink er "). ▁The ▁driver ▁of ▁the ▁trailing ▁car ▁wa its ▁until ▁the ▁adjacent ▁l ane ▁is ▁clear ▁and ▁moves ▁so ▁that ▁the ▁tr uck ▁driver ▁sees ▁his ▁or ▁her ▁car , ▁thus ▁prevent ing ▁anyone ▁from ▁standing ▁next ▁to ▁the ▁tr uck . ▁Then ▁the ▁trailing ▁car ▁moves ▁a ▁little ▁back ▁to ▁stay ▁clear ▁of ▁the ▁tr uck ' s ▁path . ▁As ▁soon ▁as ▁the ▁tra iler ▁has ▁cleared ▁the ▁obst acle , ▁the ▁trailing ▁car ▁again ▁moves ▁forward ▁and ▁flash es ▁its ▁head light s ▁to ▁inform ▁the ▁tr uck ▁driver ▁that ▁it ' s ▁safe ▁to ▁return ▁in ▁their ▁l ane . ▁A ▁pilot ▁car ▁driver ▁may ▁tempor arily ▁block ▁traffic ▁at ▁inter sections ▁to ▁ensure ▁the ▁safe ▁passage ▁of ▁the ▁tr uck . ▁ ▁Haz ards ▁ ▁O vers ize ▁loads ▁present ▁a ▁ha z ard ▁to ▁road way ▁structures ▁as ▁well ▁as ▁to ▁road ▁traffic . ▁Because ▁they ▁exceed ▁design ▁clear ances , ▁there ▁is ▁a ▁risk ▁that ▁such ▁vehicles ▁can ▁hit ▁brid ges ▁and ▁other ▁overhead ▁structures . ▁Over - height ▁vehicle ▁impact s ▁are ▁a ▁frequent ▁cause ▁of ▁damage