This is also a pedestrian safety issue because motorists often continue to turn right even after the arrow turns red, conflicting with the WALK signal.

Thanks for your report. The green left-arrow for the turns from Dover onto Mass Ave runs longer because it does not conflict with the crosswalk across Mass Ave (like the right turns do) so we’re able to program it to run while that WALK signal is on. We will examine the signal timing to see if adjustments can be made to better accommodate Dover St and (to address another point brought up in the comments) possibly change phase order (the sequence that the signal follows) so that the WALK signal across Mass Ave does not come up directly after the Dover St right-turns.