WEST BOYLSTON — The state Department of Transportation will close the southbound ramp from Route 12 to Interstate 190 Wednesday for construction work.The ramp, which is at I-190’s Exit 4, will be closed from 10 a.m. to 2 p.m.During the closure, traffic seeking to access I-190 south will be detoured to West Mountain Street.Signs, message boards and police will guide drivers through the detour.