▁all ▁other ▁state ▁roads ▁in ▁the ▁state . ▁The ▁department ▁tracks ▁the ▁traffic ▁volumes ▁along ▁all ▁state ▁high ways ▁as ▁a ▁part ▁of ▁its ▁maintenance ▁respons ib ilities ▁using ▁a ▁metric ▁called ▁average ▁annual ▁daily ▁traffic ▁( A AD T ). ▁This ▁measurement ▁is ▁a ▁calculation ▁of ▁the ▁traffic ▁level ▁along ▁a ▁segment ▁of ▁road way ▁for ▁any ▁average ▁day ▁of ▁the ▁year . ▁In ▁ 2 0 1 0 , ▁IN D OT ▁figured ▁that ▁the ▁lowest ▁traffic ▁levels ▁were ▁ 7 8 0   ve h icles ▁and ▁ 1 7 0   com mer cial ▁vehicles ▁used ▁the ▁highway ▁daily ▁between ▁Et na ▁Green ▁and ▁County ▁Road ▁ 9 0 0 ▁North ▁in ▁Kos cius ko ▁County . ▁The ▁peak ▁traffic ▁volumes ▁were ▁ 2 1 , 8 6 0   ve h icles ▁and ▁ 3 , 1 9 0   com mer cial ▁vehicles ▁A AD T ▁along ▁the ▁section ▁of ▁SR   1 9 ▁concurrent ▁with ▁Cass opol is ▁Street ▁in ▁El kh art . ▁ ▁History ▁The ▁route ▁that ▁SR   1 9 ▁takes ▁today ▁was ▁first ▁signed ▁in ▁ 1 9 1 8 ▁as ▁SR   5 1 ▁and ▁went ▁from ▁SR   2 ▁in ▁El kh art ▁to ▁the ▁Michigan ▁state ▁line . ▁This ▁section ▁was ▁ren umber ▁in ▁ 1 9 2 6 ▁to ▁U . S . ▁Route ▁ 1 1 2 . ▁In ▁ 1 9 2 8 , ▁SR   1 9 ▁was ▁first ▁signed ▁from ▁N app ane e