THE TOBIN BRIDGE, which opened in February 1950, is approaching  its projected 70-year lifespan. Perhaps it is time to consider an alternative to the never-ending series of increasingly costly and traffic-disruptive bridge repair projects, including the recent three-year restoration and rehabilitation project costing nearly $42 million and its predecessor, completed at a cost of $95 million, also for structural repairs and repainting. That project was necessary to repair floor beam fissures and other structural deficiencies.

The costs of these periodic complex maintenance and repair programs are estimated to increase by 10 percent per year to maintain the bridge’s 15 concrete piers, 92 steel columns, roadway surfaces, and other components, consistent with older steel bridges.

The Tobin Bridge’s massive steel structure — twice as long as the Brooklyn Bridge and longer than the Golden Gate Bridge — is subjected to extensive deterioration primarily from two factors, the bridge’s location in a saltwater environment and winter road de-icing materials. As a former member of the Massachusetts Port Authority board, I remember reviewing the agency’s monthly facility engineering reports, including those of the Tobin Bridge. Each month the bridge’s structural integrity status reports indicated continued deterioration, which led to substantially increased repair budgets.

According to the Non-Destructive Testing Resource Center, the average lifespan of the country’s 578,000 highway bridges is about 70 years beyond the point at which fatigue cracking and corrosion become nearly impossible  to correct.

I believe the Commonwealth should immediately begin the planning process to replace the Tobin Bridge with a tunnel. A tunnel  would have major public policy benefits, the most important of which would be the planned replacement of this most important piece of transportation infrastructure, which carries 30 million vehicles annually, before it must be severely restricted or closed altogether due to progressive corrosion and other defects. Such a planned approach would allow for continuation of existing traffic while  construction of a new tunnel is completed.

A bridge replacement tunnel would provide other public benefits, primarily for the Chelsea and Charlestown communities, which were torn apart by the Tobin Bridge’s construction from 1947 through 1950. The huge swaths of land taken from both densely populated neighborhoods for the Tobin Bridge severely impacted both communities, eliminating numerous tax-producing properties, destroying many homes and businesses, restricting economic development, and preventing the creation of environmental enhancements such as parks and waterfront access.

Replacing the Tobin Bridge with a tunnel would provide the opportunity for both Chelsea and Charlestown’s 60,000 residents to begin rebuilding their neighborhoods to make up for over half a century of social and economic deprivation.

The most feasible method for constructing a tunnel to replace the Tobin Bridge would be through a public-private partnership, which has become increasingly popular around the world as a preferred infrastructure funding mechanism. There are many successful examples, including  the Elizabeth River Tunnels Project in Virginia,which involves construction of a new one-mile tunnel, rehabilitation of two existing tunnels, and construction of associated roadways. Total project cost is $3.67 billion, including $1.47 billion for design and construction and $2.2 billion for operation and maintenance over the 58-year project lifespan. Public   contributions from the Commonwealth of Virginia comprise one-quarter of the construction costs.

A similar public-private partnership tunnel project is the Port of Miami Tunnel project consisting of two new bored tunnels serving the port’s various maritime facilities, new roadway connections to the local interstate highway system, and widening of an existing causeway bridge. The project was completed in 2014 at a total construction cost of $667 million and a 30-year operations and maintenance agreement with the private concessionaire who contributed significantly to the project’s construction costs.

These and other successful large complex public-sector projects have demonstrated the viability of public-private financing models. Massachusetts should commit to replacing the Tobin Bridge with a tunnel to prevent inevitable costly structural repair projects and traffic disruption while presenting the opportunity for Chelsea and Charlestown to rebuild their communities.

Now that Massachusetts is on the verge of receiving significant amounts of federal infrastructure funds,  and with the possibility of augmenting the federal funds with a public/private partnership program, the time is ripe for pursuing the Tobin Bridge to tunnel concept.

John Vitagliano is a former Boston transportation commissioner and a former member of the Massachusetts Port Authority board. He also served on the Massachusetts Public-Private Partnership Oversight Commission and worked as the tunnels superintendent for the Massachusetts Turnpike Authority.