Strong growth in suburbs along the route, and increased freight through the Port of Melbourne, means that the corridor is experiencing traffic congestion during peak periods, is vulnerable to short-term interruptions, and is rapidly approaching capacity. Proposals to abate congestion by allowing more traffic have included bridge widening, a tunnel underneath the river, or adding a second deck to the bridge. Many such plans have come under fire from community groups such as the Public Transport Users Association and Environment Victoria, which advocate investment in alternative forms of transport.