Connaught Tunnel is supplemented by the Mount Macdonald Tunnel.
Connaught Tunnel . In the late 1980s , the Mount Macdonald Tunnel was built to supplement the Connaught Tunnel and to lessen the grade on the eastern approach to the pass . Trains now predominantly travel east through the Connaught Tunnel and west through the Mount Macdonald Tunnel . Mount Macdonald Tunnel . The Mount Macdonald Tunnel supplements the nearby Connaught Tunnel that the CPR opened in 1916 .