interesting new cab accessory

Today I was waiting to cross State St. and noticed an interesting accessory on a passing Globe Taxi.  On each side, there was an outside mirror on the pillar between front and rear doors, positioned for passengers to be able to look for traffic approaching from behind before opening doors.  Looked like a nice addition for dooring prevention.

I hope that we'll see these on more cabs in the future.  If I get a chance to get a picture, I'll add it later.