Bike/Ped bridge underpasses on Cape Cod

Last month while on Cape Cod I had the pleasure of biking on the Cape Cod Rail Trail for the first time. It was clean, safe, beautiful, and welcoming to people walking, biking, and riding skateboards at speeds from 1 to 20 mph. Birds, rabbits, and turtles were on or near the path, adding nicely the connection with the natural world.

An enjoyable engineering feature was the underpasses that allowed travelers on the rail trail to continue their voyages without having to cross the busy roads above.

I have no idea how much money it cost to build these underpasses on Cape Cod, and I have no idea how much it would cost to add underpasses to the Charles River bridges that connect Allston and Cambridge and will soon get their once-in-a-lifetime reconstructions. But at the very least it seems reasonable to have a public and open discussion with MassDOT, DCR, and other interested parties about the cost, the design, and how underpasses might, or might not, improve the Anderson, Western Ave, and River Street bridges.