The Manager's report back on the intersection of Rindge Avenue and Cedar Street with a goal of clarifying traffic patterns through the intersection

Existing Conditions

Figure 1 Rindge Ave, Cedar St, and Middlesex St (Figure 1) is a four-leg intersection with STOP sign control on the Cedar St and Middlesex St approaches and free-flow along Rindge Ave. The northern leg of the intersection, Cedar St, is slightly offset (approximately 60ft centerline-to-centerline) from the southern leg, Middlesex St. drivers traveling north/south through the intersection must first turn right onto Rindge Ave and then left onto Cedar/Middlesex.

Cedar St also has two approach lanes, a left turn and a right turn, which feed into Rindge Ave. There are crosswalks across every leg of the intersection as well as curb extensions at three corners to improve sight distance at crosswalks adjacent to parking lanes.

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Crash Data

There was one reported crash in the Cambridge Police Department database within the past three years at this intersection. The collision involved the driver of a box truck who sideswiped the driver of a passenger vehicle while both motorists were queued side by side on the Cedar St approach to Rindge Ave. The driver of the box truck left the scene without waiting for police or exchanging information with the other motorist. This does not represent a significant crash history; therefore any improvements at this intersection would be focused on clarifying right-of-way and reducing confusion.

All-Way STOP Analysis

The Traffic, Parking, and Transportation Department (TP&T) installed Automated Traffic Recorders (ATRs) across each leg of this intersection to collect vehicular volumes over a 48 hour period and conducted Turning Movement Counts (TMCs) during the morning and evening peak-hour for vehicular, pedestrian, and cyclist volumes and directionality. From the data collected, the traffic volumes are too low to be considered for installation of a traffic signal, but meet the thresholds for an all-way STOP, as detailed below.

Following an engineering study, all-way STOP control for an intersection is considered when traffic volumes entering the intersecting streets are roughly equal and the following criteria are met:

C. Minimum volumes: 1. The vehicular volume entering the intersection from the major street approaches (total of both approaches) averages at least 300 vehicles per hour for any 8 hours of an average day, and 2. The combined vehicular, pedestrian, and bicycle volume entering the intersection from the minor street approaches (total of both approaches) averages at least 200 units per hour for the same 8 hours, with an average delay to minor-street vehicular traffic of at least 30 seconds per vehicle during the highest hour.

These data support the addition of STOP control on Rindge Ave to make this intersection an all-way STOP. In order to convert this intersection to all-way STOP control TP&T would need to remove the existing Pedestrian Warning Signs—which indicate uncontrolled crosswalks—along the Rindge Ave approaches and install STOP signs and STOP bar pavement markings on Rindge Ave eastbound at Middlesex Street and on Rindge Ave westbound at Cedar Street.

Level of Service (LOS)

Figure 2 below shows the Level of Service (LOS) by approach under existing conditions versus (proposed) all- way STOP control. LOS is a measure of delay for vehicular traffic, describing the time a driver must wait at a STOP sign or traffic signal prior to proceeding through the intersection. LOS is rated on a scale of A through F, with A representing very low delay and F representing a high level of delay. Typical peak period LOS in Cambridge at major intersections ranges from LOS D to LOS F.

Existing traffic flow along Rindge Ave operates at LOS A with little delay and the side streets (Middlesex St and Cedar St) operate at LOS E and F for the morning and evening peak, respectively. With the addition of STOP signs for Rindge Ave, the eastbound and westbound LOS drops to B and D, respectively, in the morning and C for both directions in the evening. All-way STOP control is a substantial benefit to the side streets, Middlesex St and Cedar St, increasing their LOS from E & F in the morning and evening to B & C.

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Figure 2 It should be noted that reducing the delay for users of the side street may result in a higher volume of traffic using Middlesex Street as a cut-through route during the peak hours.

Conclusion

Based on the data collected and the analysis of the intersection with and without all-way STOP control, TP&T proposes implementation of STOP signs and the appropriate pavement markings on the Rindge Ave approach to convert this intersection to an all-way STOP. This will provide clear right-of-way between vehicles on all four approaches and improve driver yielding for pedestrians at crosswalks. Prior to moving forward, we plan on scheduling an open house for members of the local community so they can understand the potential impacts of the proposed changes prior to implementation.

Time of Day

Approach

Delay (s)