About 50 traffic cones that had been placed along the Massachusetts Avenue Bridge between Cambridge and Boston were grabbed from the busy roadway and thrown onto the Charles River below.
"It's probably kids getting drunk," said bicyclist Ron Dion. "Having a good time, hopefully that's it … punks."
The cones are part of a pilot program to widen the bike lane on the bridge. The project means the bridge is down to one lane in each direction for cars, and some wonder if the vandalism is anti-biker sentiment.
"I feel like the cars, pedestrians, they don't even care if you're biking, they feel like the bikers just aren't important," said bicyclist Eric Chan. "While I'm biking, I always keep myself more aware and try to stay as safe as possible."
State transportation officials say the vandalism happened twice over the weekend: overnight Friday into Saturday and then again Sunday into Monday.
Jonathan Gulliver, the state's highway administrator with the Massachusetts Department of Transportation, tweeted, "This creates a hazard for all road users and is polluting the Charles. Anyone with information on this should contact law enforcement."
Becca Wolfson, executive director of the Boston Cyclists Union, says since the program has been up and running for two months, she doesn't think whoever threw the cones over the bridge did it out of spite for bikers.
"I could see drivers being a lot angrier if it was leading to catastrophic congestion and traffic jams," said Wolfson. "But actually, there's hardly any impact on anyone driving or using the bridge at all."
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Transportation officials are studying whether to turn the cones into a more permanent structure.
It's being studied through the winter.