On Thursday, October 30, the City of Cambridge’s contractor, MIG Corporation, will close the westbound portion of the Cambridge Street Tunnel (traveling towards Harvard Square), in order to place new concrete wearing surface. The westbound lanes will be closed from 4am – 3pm. Motorists traveling in the eastbound lanes will not be impacted. Message boards and detour signs will be highly visible during this closure. Emergency vehicles will maintain access at all times.