or ▁as ▁many ▁as ▁there ▁are ▁lan es ) ▁start ▁at ▁a ▁time , ▁and ▁rotate ▁through ▁all ▁the ▁lan es , ▁before ▁being ▁replaced ▁by ▁the ▁next ▁set ▁of ▁drivers . ▁This ▁is ▁known ▁as ▁a ▁" he at " ▁or ▁" con si ". ▁O ften ▁a ▁small ▁amount ▁of ▁practice ▁time ▁( us ually ▁ 3 0 ▁seconds ) ▁will ▁be ▁given ▁to ▁the ▁drivers ▁prior ▁to ▁the ▁start ▁of ▁each ▁heat . ▁If ▁there ▁are ▁an ▁odd ▁number ▁of ▁drivers ▁such ▁that ▁they ▁are ▁not ▁wh olly ▁divis ible ▁into ▁the ▁number ▁of ▁lan es , ▁one ▁of ▁two ▁measures ▁is ▁taken : ▁either ▁a ▁heat ▁is ▁run ▁with ▁one ▁or ▁more ▁positions ▁un filled , ▁or ▁a ▁heat ▁is ▁run ▁with ▁extra ▁drivers , ▁with ▁a ▁" s it - out " ▁position . ▁After ▁all ▁drivers ▁have ▁run ▁their ▁heat , ▁pla cement ▁is ▁determined ▁by ▁total ▁la ps ▁completed . ▁ ▁O ften ▁round ▁rob ins ▁are ▁modified ▁to ▁include ▁a ▁" main " ▁and ▁sometimes ▁also ▁a ▁" last - ch ance " ▁heat . ▁When ▁run ▁with ▁a ▁main , ▁the ▁round ▁ro bin ▁is ▁run ▁as ▁normal , ▁but ▁at ▁the ▁end ▁the ▁top ▁compet itors ▁( as ▁many ▁as ▁there ▁are ▁lan es ) ▁run ▁an ▁extra ▁heat . ▁This ▁heat ▁is ▁usually ▁longer ▁( 3 ▁to ▁ 5 ▁minutes ▁per ▁segment , ▁ 1 . 5 ▁" pit " ▁time , ▁and ▁ 1 ▁minute ▁practice ▁before ▁the ▁heat ). ▁At