Stripes on major thoroughfares do not protect cyclists. Sharrows (those big arrows with a bike symbol painted on the road) are not meant to be used on busy streets. Rather, according to many bike experts, they are meant only for the less-traveled side streets. Exhorting motorists and bicyclists to be careful just isn’t enough when there isn’t enough room for both cars and cyclists.
Boston is spending lots of money painting streets and putting up signs, but ultimately if we want to prevent yet another accident, we need to provide dedicated lanes or perhaps have cyclists carefully share the sidewalks with pedestrians.