▁in wards ▁had ▁previously ▁lost ▁most ▁of ▁their ▁rid ership ▁to ▁street c ars ) ▁while ▁providing ▁a ▁faster ▁trip ▁than ▁on ▁surface ▁trans it . ▁ ▁However , ▁other ▁extensions ▁received ▁priority , ▁and ▁the ▁W ob urn ▁extension ▁was ▁not ▁built . ▁The ▁B & M ▁dropped ▁the ▁Som er ville ▁local ▁stops ▁in ▁the ▁late ▁ 1 9 4 0 s ▁and ▁early ▁ 1 9 5 0 s ▁due ▁to ▁decl ining ▁rid ership . ▁In ▁ 1 9 5 5 – 5 7 ▁the ▁B & M ▁raised ▁the ▁tracks ▁through ▁ ▁and ▁ ▁onto ▁a ▁high ▁grade ▁and ▁vi ad uct ▁in ▁order ▁to ▁eliminate ▁busy ▁grade ▁cross ings . ▁However , ▁the ▁elev ated ▁portion ▁was ▁only ▁built ▁with ▁two ▁tracks , ▁prevent ing ▁a ▁rapid ▁trans it ▁extension ▁from ▁reaching ▁to ▁W ob urn , ▁since ▁two ▁tracks ▁would ▁still ▁be ▁needed ▁for ▁Low ell ▁Line ▁service . ▁All ▁discussion ▁of ▁the ▁project ▁since ▁has ▁focused ▁on ▁an ▁extension ▁no ▁further ▁than ▁West ▁Med ford . ▁The ▁track less ▁t rolle ys ▁were ▁replaced ▁by ▁bus es ▁in ▁ 1 9 5 9 ▁and ▁ 1 9 6 3 , ▁leaving ▁most ▁of ▁Som er ville ▁with ▁a ▁trans it ▁system ▁dependent ▁on ▁bus es ▁running ▁on ▁frequently ▁crow ded ▁streets . ▁ ▁Original ▁GL X ▁project ▁plan ▁ ▁After ▁dec ades ▁of ▁no ▁action , ▁in ▁ 1 9 9 0 ▁Massachusetts ▁agreed ▁to ▁a ▁leg ally ▁binding ▁resolution ▁to ▁extend ▁the ▁line ▁through