So, these signals have been bothering me for a while. The first one,
I finally partially figured out, but I still think it's inefficient.
The second one, is just WRONG.
Anyway. This is the intersection of the one-way Dover Street with
Mass Ave, in Cambridge. At the intersection, Dover is two lanes -
one left turn lane, one right turn lane.
When it's time for Dover Street to go, you get a green right arrow
only first, and then a green left arrow only. At neither time does
any other lane have a green light. The only reason for this somewhat
perverse splitting up of the leftgoers and the rightgoers is that the
crosswalk is on the right, and they get a walk light during the
left-only light. But there's no reason that the leftgoers couldn't be
going while the rightgoers are already going. There's no crosswalk on
the left, and none of the cross traffic is going. Also, I think this
is more concern for the people in the crosswalk than Mass Ave shows
anywhere else - pretty much everywhere else, it's perfectly happy to
have the walk light on a straight-plus-turning-included green. And
the crosswalk two down has no lights at all, it's just "cross when it
doesn't look like anyone is going to kill you." Not that I object to
doing something nice for the pedestrians, but it surprises me because
it's so unusual. I do object to being inefficient with the
leftgoers, though. :)
The other Intersection of Inexplicability is four blocks down, at
Cameron and Mass Ave. Let me describe the intersection. Mass Ave
is two lanes on either side of the divider. Cameron Ave, to the
right, is one of the more major smaller roads - it's a snow emergency
route, it's the first through street past the bike path, it has a lot
of traffic. To the left is Harvey Street, which is tiny and one way
away from Mass Ave. I used to say that I never saw anyone turn left
onto Harvey Street, but while I was hanging around taking pictures, I
did finally see one person do so.
Anyway. When the light turns green on Mass Ave, the northbound folks
briefly get this set of lights before the full green:
I can kind of see the point in giving someone the chance to take the
left before the oncoming traffic gets to go, in case there's a lot of
traffic. But why give the left to Harvey Street, rather than to the
people going south who might want to turn left onto the much more
travelled Cameron? But that's not even the real question. The real
question is, why on earth is there a left arrow from the right lane?
You can have two lanes of left turning people when you have a lot of
people wanting to turn left and the leftmost lane is a dedicated
left-turn-only lane. (Like going from Mass Ave left onto Somerville
Ave, in Porter Square - there's a left turn lane and then a
left-and-straight lane and then a straight lane. But it makes no
sense at all here. The left lane isn't left turn only. Almost nobody
turns left. Harvey street has only one lane, it doesn't have room for
two lanes worth of left turners at once. Turning left from the right
lane would be the worst idea ever. So.... what the heck?