Old Colony Ave is currently a 2+2 distributor road along residential roads with local businesses on the main drag. It has large sidewalks and a median that we preserve in our new design.

Our new design includes demoting the road to a 1+1 travel lanes. In the new space we will be putting in 5-foot wide one-way cycle tracks, buffered by 5 feet of grass with trees, and 7-feet parking lanes on the other side of that. We will keep the 8-feet sidewalks as well. In the travel lanes, they will come down to 10 feet with a 10-feet median that will turn into a left-turn lane at major intersections. Cycle track lanes and the buffer will stay the same through the intersections, but tree linings will end to provide better visibility.

Existing Old Colony Avenue

At the northern end of Old Colony Ave, it meets Dorchester Ave to make a new upper Dorchester Ave section. This 2+2 section has a varying cross-section with changing widths, causing the bike lanes to be broken up, turned in sharrows, or just go missing completely from the road.

Our new design varies as the width of the road changes. On the narrowest section, a 10′ wide shared path will be implemented on either side. The cyclists will ride up onto the sidewalk, with signage warning pedestrians and cyclists that they are sharing this path. This section of road is a bridge so there are no businesses and therefore few reasons for pedestrians to be walking here. With little conflict between bicycles and pedestrians, we believe this option will still be the safest and least stressful for the cyclists along this route. A bike lane was out of the question, so this was the most desirable design. This is shown in the first proposed cross-section, between Dorchester Ave and A Street.

At the wider sections, between A Street and West 4th, the cycle track continues. We’ve also taken advantage of the space by restoring the trees and allow cyclists a buffer between them and the parked cars along the travel lanes. Unfortunately we do lose some of this space after the intersection, but enough is retained to keep a cycle track and even parking spaces for the offices along the road.

Existing Sections of Upper Dorchester

(between Dorchester Ave and A Street)

(between A Street and West 4th)

(between West 4th and Broadway)

The intersections we redesigned are Dorchester Street, D Street, Dorchester Ave, A Street, West 4th Street, and West Broadway. These are all major crossings where cyclists and pedestrians cross more than 2 lanes of traffic.

To ensure a safe and low-stress route for a cyclist’s entire ride, we are also implementing Dutch-inspired protected intersections at every major crossing. These will be at Dorchester Street, D Street, A Street, West 4th Street, and West Broadway. Dorchester Avenue will have a roundabout, shown below. The protected intersections are designed with a small median is in the corner between the turning cars and cyclists. This forces the cars to slow down for a sharper turn, and pushes the cyclists out to the right to give the drivers a better view of the incoming cyclists to avoid right-hook collisions.

Dutch protected intersection inspiration:

At the intersection between Old Colony Ave and Dorchester Avenue we took inspiration from a Dutch turbo roundabout. The roundabout will allow us to remove the traffic signal and increase capacity while keeping to our one lane design on Old Colony Ave. This Semi roundabout lets cars come with minimal conflicts through the intersection without stopping, however the curves in the road slow down vehicle traffic. Bikes and pedestrians benefit from this layout by both the reduction of delay and the reduced interaction with cars as more space is provided between the forms of transportation and the number of conflict area in reduced.

All entries to the roundabout will be perpendicular on the approach, forcing cars to slow down to make a sharp turn. (This may not be accurately depicted in the CAD drawing but the geometry can be easily fixed). There is curvature throughout the travel lanes. Pedestrian and bicycle crossings will be safe due to crossing tables, splitter islands, and the previously mentioned reduced speed of cars. It is important that crossings are unsignalized to preserve the good traffic flow provided by the roundabout.

Capacity was determined by the critical movements, the highest volumes of movements that would conflict with each other.  For the proposed semiroundabout intersection, making the Southbound thru and Northwest bound thru movements non-critical by removing them from conflicts with the other directions greatly expanded the capacity of the intersection

Semi- Roundabout Traffic Capacity

Dutch Oval Roundabout Inspiration

How capacity will still work:

The arrow diagram shows the major movements through the Dorchester Street intersection. What creates the most constraint on capacity in our proposed condition is the changing of the lane configuration on Old Colony Ave. Capacity was determined by the critical movements, the highest volumes of movements that would conflict with each other.  Although the intersection is very slightly above capacity in the proposed condition, we are anticipating a 10% reduction in traffic due to demotion of the existing Old Colony Ave-Morrissey Boulevard corridor. This process will discourage regional thru traffic from using the corridor, in favor of the I-93 corridor which runs parallel from the South Shore into Downtown Boston.