Hearken back to Star Trek II, the Wrath of Kahn, when Spock advises Kirk
"He's intelligent but not experienced. His pattern indicates two-dimensional thinking."
Kirk "got" it and defeated Kahn.
Watch - http://www.youtube.com/watch?v=iPQfwmfRq2s
Perhaps MassDOT and Arlington's engineers are thinking like Kahn and would benefit from taking a step back from the two-dimensional drawing board to consider a solution based in the Z (vertical) direction.
This is not science fiction, European cities are installing "floating suspension bridges that let cyclists sail over car traffic." From Boston Cyclists Union:
"Eindhoven's "floating saucer" bridge nominated for a Dutch Design Award this month. This has to be one of the coolest pieces of bike infrastructure in the world."
Read the article and see images at http://gizmodo.com/a-floating-suspension-bridge-that-lets-cyclists-sail-ov-1453401188