Laura rants about traffic lights

[firstfrost]

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?

Comments

[jadia.livejournal.com]

Traffic signals around here are insane. It's the only place I've seen both red and green lights at the same time and it took a while to figure out! The northbound mass ave light near Harvard Sq. is also horribly confusing in the same way that the Dover St. light is - what I like best is when you have red and yellow at the same time. :p

Incidentally, for the 2nd intersection that you are talking about, the southbound traffic does actually get a dedicated left onto Cameron - I use that fairly often. :) It just happens *after* the northbound traffic gets to go.

I also didn't think that 2 traffic lights would mean one is for each lane - I just always thought it was to increase visibility of the lights, just in case. (In case of what, I don't know...crazy drivers, maybe.) In fact, there is a road near where I work (Hartwell Ave) which has 2 traffic lights on it, but the road is only lane-marked as 1 lane. (Practically speaking though, it's actually 1.5 lanes, and it's used as "2-lanes-with-no-shoulder" during rush hour.) The fact that the road has 2 traffic lights side by side was used as an argument that it's actually a 2-lane road, despite having no lane markers. (I think now it's been marked as a 1-lane road right where there are 2 traffic lights...talk about confusing.)

[dcltdw]

Dover St: there's a cross-street to Mass Ave ahead and to the right from Dover that has signals at the same time. I believe they have the same signals -- so if Dover has the R arrow, the opposite street also has R arrows. This is because if it was just a generic green, the L turning people out of Dover would not necessarily expect R turning people, because that traffic is not precisely opposite them.

Cameron Ave, I'm not familiar with since they changed that intersection.

[hr-macgirl.livejournal.com]

These lights are in Cambridge, yes?

I'm emailing you with the details of The Guy to contact in Cambridge to ask about this intersection. He's the Traffic Engineer for the city responsible for traffic signals. He can explain every signal and the reasoning behind the cycle.

[mathhobbit.livejournal.com]

Why did you leave out the light I have to go through to park at your house, at which traffic going in two different directions has the right-of-way. (I think it's left turners and the crosswalk they're turning across that share right-of-way, but that intersection is so confusing that I've never been sure.)

[brass-rat.livejournal.com]

I think others have covered the comments that I would have made about these two intersections. Neither of them actually bother me that much.

The one I hate (and I'll admit I haven't checked that its still broken recently) is by the Galleria in East Cambridge. If you're traveling west on Cambridgeside Place, at 1st street, when you get a green light, you see a green right arrow and a green left arrow (and no green circle. When I asked the city about it, they said it was to help alleviate people going straight which would put them the wrong way on a one-way street. The problem is that east bound traffic also has a green light then, meaning that you have a green left arrow, but the left turn isn't actually protected.

I also think that every light on Oxford street could be replaced with either a 4-way stop, or a yellow-flashy in one direction and a red-flashy in the other and greatly improve things, but I haven't actually talked to the city to find out whether there's something I'm missing (pedrestrian traffic at the park being the main one I can think of).