1 3 1 ▁in ▁this ▁section ▁but ▁is ▁not ▁sign post ed . ▁IN D OT ▁surve ys ▁the ▁roads ▁under ▁its ▁control ▁on ▁a ▁regular ▁basis ▁to ▁measure ▁the ▁amount ▁of ▁traffic ▁using ▁the ▁state ' s ▁high ways . ▁These ▁traffic ▁counts ▁are ▁expressed ▁in ▁terms ▁of ▁annual ▁average ▁daily ▁traffic ▁( A AD T ), ▁a ▁calculation ▁of ▁the ▁average ▁daily ▁number ▁of ▁vehicles ▁on ▁a ▁segment ▁of ▁road way . ▁The ▁ 2 0 0 7 ▁survey ▁reported ▁average ▁daily ▁traffic ▁of ▁ 7 , 9 4 9   c ars ▁and ▁ 2 , 0 6 8   tr uck s . ▁ ▁South west ▁Michigan ▁ ▁As ▁a ▁state ▁tr unk line ▁highway , ▁US   1 3 1 ▁runs ▁approximately ▁ ▁in ▁Michigan , ▁from ▁the ▁Indiana ▁state ▁line ▁north ▁to ▁Pet os key . ▁ ▁The ▁highway ▁is ▁an ▁important ▁link ▁between ▁Grand ▁Rap ids ▁and ▁the ▁tour ist ▁areas ▁of ▁Northern ▁Michigan . ▁The ▁tr unk line ▁enters ▁Michigan ▁about ▁three ▁miles ▁() ▁south ▁of ▁White ▁P ige on , ▁crossing ▁a ▁branch ▁of ▁the ▁Michigan ▁Southern ▁Rail road ▁before ▁meeting ▁US   1 2 ▁on ▁the ▁west ▁side ▁of ▁the ▁village . ▁The ▁highway ▁passes ▁through ▁rural ▁far ml and ▁north ▁to ▁ ▁just ▁south ▁of ▁Const antine , ▁where ▁US   1 3 1 ▁turns ▁north west ward ▁to ▁by pass ▁the ▁dow nt own ▁business ▁district , ▁cross es ▁the ▁St . ▁Joseph ▁River ▁and ▁continues ▁north ▁to ▁Three ▁R ivers