Scott, the standard for lane usage signs is to post them before you reach the intersection. It does take drivers several weeks (and often, months) to learn traffic changes. I have noticed it's gotten much better, although of course you will occasionally see a driver trying to go through from the right-only lane. At this point, I think these people know exactly what they are doing -- i.e., trying to cut in line.

Jeffrey R. Parenti, P.E.
Traffic Engineer

Jeffrey,

Thanks for your comments. You're right -- it has gotten much better since the pattern change was implemented. Where I often see problems still are in two situations, both when traffic is backed up beyond Green Street:

1. Buses coming from Green Street that need to continue straight on to Prospect Street have a really hard time changing lanes, if not an impossible time.

2. When traffic is backed up past Green Street, those not familiar with the intersection (visitors, tourists, delivery drivers, etc) don't know that a right-turn only lane is about to hit them. When the cross Green Street, there's sometimes a frantic desire to change lanes to not violate the rule -- or they just continue straight and try to merge.

Yes, there's some who cut the line on purpose -- but when traffic is backed up beyond a block, there's no real incentive to do that. It's just confusion.

What can be done to inform people earlier in this sort of situation?

Thanks again for your response!

Scott-

We talked about posting another lane usage sign upstream of Green Street, but the problem with that is it suggests that you can turn right into Green, which of course is one-way. So that would create a new problem.

I could solve this problem outright by using a lane drop/add -- that is, merge down to one lane and then open up to a right-turn only lane. (See an example of an drop/add just east of Sidney Street on Mass Ave. However, I don't think drivers would like that very much and they would decide to drive right over (and quickly rub out) the paint.

There aren't many places in Cambridge where there is such a short block leading to a busy traffic signal, but where I do have them (Mass between Somerville Ave. and Upland in Porter Square is a classic example), it presents a huge challenge. In these situations, I find there is almost never a 100% solution for all problems.

Jeffrey R. Parenti, P.E.
Traffic Engineer

Thanks for your reply to this thread and others, Jeffrey. What about a custom sign? I've attached a really bad sketch I did that I'm sure violates every standard you have -- but perhaps you get the idea?

I feel like I've seen similar signs before. For example, there are custom signs at the huge Davis Square intersection in Somerville that show how traffic flows. Perhaps a sign indicating that there are turn restrictions ahead but also show Green Street? Thank you for putting thought into the design at this spot.

Scott-

That's not bad! We certainly do make custom signs, and the Davis Square sign is a good example. we have to keep certain minimums -- for example, for letters to be legible at, say 30 mph, they have to be a few inches tall. So the more information you have on the sign, the larger they are.

We have a computer application that helps us with sign design. We can try it and see what the size might be, and then try to find a place to post it. If it's too big, it will be winged by a passing truck.

Jeffrey R. Parenti, P.E.
Traffic Engineer

Update: we have finished paving Prospect Street just north of this location, and I am adding some new lines within this intersection that should help with this problem.

Jeffrey R. Parenti, P.E.
Traffic Engineer
City of Cambridge