Tunnel Tour questions:

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Aside from cost, what are the downsides of tunnels? How about advantages?

The website of The Automobile Association Limited of England has the following list of tunnel downsides:

• Higher building costs and difficulties of cost control during construction
• "cut and cover" tunnels can be disruptive during construction
• good standards of daily operations required
• ongoing operational costs
• underground junctions difficult and potentially expensive
• siting of portals and ventilation shafts needs to be carefully selected

There are probably other disadvantages to urban tunnels not included on their list. Examples are safety issues - emergency vehicle access, fire protection, emergency egress, and perhaps claustrophobia issues for some motorists. The Automobile Association Limited of England website also has a list of advantages to tunnels. Here are a few of my favorites:

• while vehicle emissions on surface streets flow straight into the air, harmful pollutants in tunnels can now be collected before ventilation and "scrubbed" near clean using new technologies
• techniques of tunnel construction have made major advances in recent years - in some locations, tunneling can even be cheaper than surface constructions. Real costs are falling at around four per cent per annum
• advanced countries around the globe, in town and country, are increasingly willing to pay the cost of retaining landscapes or reclaiming surface streets by moving strategic roads or major arteries underground at pinchpoints, sometimes over long lengths
• the accident rate in tunnels worldwide is half that of inter-urban roads and even less than half in urban areas

Why doesn't this plan include burying Storrow Drive behind the Esplanade?

If the section of Storrow Drive behind the Esplanade were ever buried, it would be a cut-and cover tunnel (similar to the existing tunneled section of Storrow Drive already buried to the north of Back Street between Arlington and Berkeley Street, in the Back Bay). That effort would be a different technology and venture than what is proposed here. The proposed Freshgate Tunnel would be a deep-bore tunnel. It could be built and opened with far less interference to existing traffic flows during construction than burying Storrow Drive behind the Esplanade would entail. Also, such a venture at the Esplanade would seem to be beyond the purview of Harvard University – the proposed funding source of the deep-bore tunnel in this vision. Burying the existing roadway between
the Esplanade and the Back Bay may be a good idea, but it is not the purpose of this website to advance it.

Shouldn't this proposal also include public transportation ideas along with an automobile tunnel?

Public transportation improvements definitely ought to be included in the mix of ideas to consider. Here are just two of many public transportation schemes worth pondering:

• A larger diameter tunnel with sufficient room for a third level for light rail vehicles.

For instance, the Green Line could have yet another western leg, beginning beneath Charlesgate (just to the east of Kenmore Square), and running within and beyond the Freshgate Tunnel all the way to the Red Line's Alewife Station in west Cambridge, about ½ mile from Fresh Pond. Here is a cross-section of what the tunnel might look like if a Green Line extension were included:
This Green Line extension would have intermediate stations along the Freshgate Tunnel route - perhaps at MIT, at Western Ave, at North Harvard Street, at Mount Auburn Hospital, or at Fresh Pond.

• A new, mini surface system of public transportation along some of the routes where parkways have been removed.

One of Harvard University's Allston Initiative Progress Reports described such a mini-bus transportation system called the SMRTram. A unique feature of the SMRTram is that the mini-busses run on a single narrow roadway in both directions. The mini-busses cross each other only at the stations. This narrowness of both the busses and the roadway makes SMRTrams relatively unobtrusive.

A SMRTram system could run along the entire route where Storrow Drive has been turned to parkland - from Soldiers Field to Charlesgate. The SMRTram system would provide easier public access to the new parklands where the roadway had been (important for people with disabilities, the elderly, etc.) Also, for commuters and motorists who would miss the pleasant views along Storrow Drive, a SMRTram would provide an even more pleasant and safer means of transportation along the banks of the Charles River Basin. Here is what the SMRTram looks like:

Here is another resource for public transportation options along the Charles River: Ed Nilsson, of Nillson+Siden Associates, has developed a visionary scheme for the Charles River that proposes extension of the Blue Line along the Charles. (For a link to a website showing this vision, click HERE).

Wouldn't the construction process mess up traffic?

In this vision, the entire deep-bore tunnel (and all of its entry ramps that are either deep-bore ramps or in places where traffic would be unaffected) would be totally completed before any work to change existing roads even begins. Traffic problems would be incurred only during construction of the top ends of the new ramps and interchanges. All the rest would already be completed. Still, the construction process would definitely mess up traffic for a while, but not as badly as the Big Dig has.

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