As you may recall, last fall we tried unsuccessfully to change the light phasing in Cushing Square. After several weeks of confusion and some near misses, we went back to the original, pre-project configuration.
So, currently that intersection is working as it has for many years: cars on Common Street headed towards Watertown get green left and green straight at the same time while cars headed down the hill into Belmont get red. Then, that reverses. This is very inefficient because most of the traffic in both directions would like to go straight. One wants the two straight movements to share green time.
After a lot of debate, a new approach has emerged which should be clear for drivers and is actually more efficient than any of the previously attempted configurations.
The engineer’s explanation of this new approach appears below (with some additions from me):
- For the vehicles going east or west on Trapelo Road there will be no change.
- The south bound (up-hill toward Watertown on Common Street) lights will have a left arrow and a green ball light that still turn green simultaneously.
- But, the south-bound green arrow will turn to red while the south bound straight ball light remains green. Vehicles on Common Street heading toward Watertown will be able to continue towards Watertown. But vehicles in the left turn lane and turning left onto Trapelo Road will have to stop before the Common Street through movement stops.
- When the south-bound left arrow goes red, the north-bound (downhill from Watertown on Common Street) lights will go green for both north bound lanes. For south bound vehicles on Common Street in the right lane and heading toward Watertown they will find that, during the latter part of their green phase, traffic will start coming from the opposite direction of Common Street and some of that traffic will be wanting to turn left in front of them.
- The north bound vehicles will see green balls only (no left arrow), as is common at many intersections. There will be a “left-turn-yield-on-green ball” sign, again as is common at many intersections. For vehicles on Common Street coming from Watertown, they will now find that traffic will be coming from the opposite direction of Common Street when they have the green indication and the vehicles turning left into Trapelo Road toward Waverley Square will need to yield to traffic coming from the other direction of Common Street.
The beauty of this approach is that (a) the signage will be simpler — the complicated signs with three-headed arrows will be less critical; and (b) if north-bound traffic makes the mistake that it tends to make — thinking that the straight move to continue on Common Street is a left turn, they will actually not conflict with the straight movement from the other direction. The only time they will need to think is when they are making the hard left onto Trapelo and on that movement, it is reasonable to expect the drivers will exercise the caution that they normally should on a left turn with no arrow.