We envision replacing two motor vehicle travel lanes on Memorial Drive with protected multi-use paths along the full length of Memorial Drive. This will allow sidewalks on both sides of Memorial Drive to be designated for pedestrian use only. Those paths should be widened and repaved so that they are safe and comfortable.
One potential design would be to have a bidirectional multi-use lane on the side of Memorial Drive that is closest to the river, leaving two motor vehicle lanes, one for each direction of travel. As needed, at major intersections, the multi-use path may be narrowed in order to create space for a dedicated motor vehicle turning lane.
What does this new vision of Memorial Drive's look like?
Section Views (As of 1/10/22)
Below are two sections for Memorial Drive.
Top Section: The top view is the one we propose as it is inexpensive, easily done, and preserves the current trees and river bank. The layout maintains the current typical roadway width and material. 14 feet of that 40 foot width is re-allocated to a bi-directional bike lane (and other micromobility modes, like skating, motorized wheelchairs, hand scooters, etc.), and a buffer between cars and bike lanes, which are on the river side edge of the road, returning more space to car-free uses. The trees on the river (south/west)sides of the road are retained, so continue to shade the cyclists and the roadway, reducing the heat island impact of the pavement.
Lower Section: The lower drawing shows the section proposed by DCR's consultant, Stantec. While it's exciting to see the car space reduced to two lanes (unfortunately with 8' of shoulder), this plan destroys the existing line of mature sycamore trees on the southwest side of the roadway, and thereby the iconic sycamore allee and any shade provided to pedestrians, cyclists and cars for decades to come. It also creates a too-steep-to-maintain river's edge slope, which has other problems as well.
Memorial Drive from Mt Auburn St to JFK St/"Lars Anderson Bridge"
DCR has already announced plans to do a road diet from JFK St west towards Mt. Auburn St.
Currently at the intersection of Memorial Drive and JFK St, near Harvard Square, only right turns are allowed; there are no left turns permitted from any direction. Space could be created, by reducing the width of the multi-use path, to accommodate vehicle traffic traveling westbound on Memorial Drive and turning right on JFK St to head towards Harvard Square.
To improve visibility of cyclists and pedestrians and reduce conflicts with turning vehicles, we propose using concrete islands (see gray ovals in the diagram below) in a "Dutch junction." These islands increase the turning radius and improve the ability of turning drivers to see cyclists and pedestrians.
Memorial Drive at Western Avenue
At Western Avenue, the multi-use path could be narrowed in order to accommodate a left turn lane from northbound Memorial Drive onto Western Avenue. The length of this left turn lane could be adjusted as deemed necessary by traffic volumes. As with JFK St, we would propose using a concrete island to increase the turning radius and improve visibility of cyclists and pedestrians for vehicles traveling southbound on Memorial Drive and turning on to Western Ave.
Memorial Drive at River Street
The design at Western Avenue could be similarly applied at River St, but to create a left turn lane from southbound Memorial Drive onto River St.
Memorial Drive at BU Bridge, Rotary, and Overpass
Thanks to Ari Ofsevit, a well-known local transportation influencer, for developing the design of Memorial Drive at the BU Bridge, Magazine Beach and the BU Rotary that would provide protected bike lanes and pedestrian access, bus priorty lanes, and motor vehicle access to the area. A major benefit of this plan and those further east is that they return acres of pavement formerly used by motor vehicles to parkland use and enables buses to travel much more quickly through the area, all while diverting car traffic from neighborhood roadways. In this plan, the BU Bridge Overpass is retained, with two lanes used by cars (one in each direction), and the other two lanes used by bicycles (also one lane in each direction.) While costs are minimized, gains are realized for all road and park users.
This overlay of the above layout shows the route of bike commuters traveling from NW to SE, ie from Harvard Sq to BU, over the BU Bridge (in black dashed lines) and potentially back (N), from BU to west over the BU Rotary Overpass toward Harvard Square (in white dashed lines).
Mass Ave ("Harvard") Bridge at MIT
This area continues to have keep automobile traffic kept on the former northern half of the roadway, returning many acres of parkland to non-car recreational and green-commuting use. This view, in partial perspective, shows the way bike and automobile lanes along Memorial Drive traveling east and west can access both the Mass Ave underpass and Mass Ave itself.
Memorial Drive East of Mass Ave
In this section of Memorial Drive east of Mass Ave, automobile lanes again share the north (MIT side) of the former roadway. The existing crossings to the former roadway on the south side are repurposed to provide car access to boathouses, and other park uses (think food trucks, bands, etc.). Memorial Drive parklands are now much safer for pedestrians, cyclists, and other users to access and navigate, and many acres of parkland that made up an unusable median are returned to the riverside park.
Ari Ofsevit has more history of the area and other perspective on this subject here: "A Two-lane Mem Drive Would Improve, Well, Everything".