Marlborough - Segment 1: Twin Peaks
Currently, CT 66 descends into the Dickinson Creek Valley on two steep hills, one on either side of the valley. There are slow vehicle lanes for the uphill direction on both hills. The western one is about 1200 feet (0.23 miles) long, and the eastern one is about 2650 feet (0.50 miles) long. At the bottom of the valley, there are two intersections about 700 feet (0.13 miles) apart.
The western intersection is a four-way intersection with Saner Rd intersecting from the north and Flood Rd intersecting from the south. Both of these roads are stop-sign controlled, and intersect CT 66 with about a 45 degree angle, requiring right turns off of CT 66 to be very sharp. These two roads also meet with enough of an offset to make it difficult for cars in opposite directions on CT 66 to make left turns. There are not large amounts of traffic exiting either Flood or Saner Roads, but traffic can stack up due to the heavy traffic on CT 66. Lines containing several waiting cars are often found on both Saner and Flood Roads during rush hour, requiring waits of several minutes.
The eastern intersection is a three-way intersection with Dickinson Rd, coming from the north. This is a standard three-way intersection, with fewer problems than the Saner Rd / Flood Rd intersection. This road has less traffic than either Saner or Flood Roads, so the stacking problem is not as large here.
There is also an intersection with Roberts Rd, which also comes from the north. Some stacking problems occur here during rush hour, but are not as bad because of the double lane on CT 66 East.
In the reconfigured design, the slow vehicle lane setup is changed. Instead of having the right lane be a slow vehicle lane, the left lane would be a passing lane. A "Keep Right Except To Pass" rule would be used here.
The Saner Rd / Flood Rd intersection would have a traffic signal installed. This is the only way to control the new left turn lanes on CT 66. Without the signal, opposing left-turning traffic may have head-on collisions. The signal would have an actuated leading left-turn phase in one direction of CT 66, and an actuated lagging left-turn phase in the other direction. Saner and Flood Roads would have actuated signals as well.
At the Dickinson Rd intersection, a left turn lane would be installed. The Roberts Rd intersection would basically be left as-is.