A communication transmitted from Louis A. DePasquale, City Manager, relative to Awaiting Report Item Number 19-51, regarding safety concerns at the intersection of Garden Street, Field Street, and Alpine Street

City of Cambridge Community Development Department Iram Farooq, Assistant City Manager Department of Public Works Owen O’Riordan, Commissioner Traffic, Parking, and Transportation Joseph E. Barr, Director MEMORANDUM To: Louis A. DePasquale, City Manager From: Joseph E. Barr, Director of Traffic, Parking, and Transportation Iram Farooq, Assistant City Manager for Community Development Owen O’Riordan, Commissioner of Public Works Date: July 24, 2019 Re: Awaiting Report 18-55: Report on Improving Road Safety Conditions on Clinton Street This memo is in response to Order 7 from the April 22, 2019 City Council Meeting (Awaiting Report 19-51) regarding safety concerns at the intersection of Garden Street, Field Street, and Alpine Street. The intersection of Garden Street at Field Street and Alpine Street (Figure 1) is controlled by a STOP sign on the Field Street (east) leg of the intersection, which is one-way westbound towards the intersection. The Alpine Street (south) leg of the intersection is one-way southbound away from the intersection. The primary movements through the intersection (shown in orange in Figure 1) travel between the Garden Street (north) leg and the Field Street (west) leg is from west to north (left curve) and north to west (right curve). Primary Movement Figure 1 – Intersection Layout

2 Signs and pavement markings are provided on both legs to clearly mark these primary movements through the intersection. These include curve warning signs on both approaches (Figure 2 and Figure 3) and dotted double yellow markings through the intersection on the curved alignment (Figure 4). This intersection was recently reconstructed as part of the West Cambridge Sewer Separation project, as shown in the before and after aerial images in Figure 5 and Figure 6. The work within this intersection substantially reduced the size of the paved vehicular area, removing over 2,200 square feet of asphalt to provide additional pedestrian space and curb extensions. The existing crosswalks were reduced in length by 40 to 50 percent and an additional crosswalk was added across the north leg of the intersection. The crosswalk across Alpine Street was raised in order to reduce the speed of turning vehicles. The photos below show the significant improvement to the intersection geometry. Crash data from the Cambridge Police Department indicate that there were zero reported crashes at this intersection from 2016 through 2018. Figure 3 – Garden Street Curve Sign Figure 2 – Field Street Curve Sign Figure 4 – Intersection Lane Markings

3 In order to consider all-way STOP control, the intersection must meet certain warrants set forth under the federal Manual on Uniform Traffic Control Devices (MUTCD), 2009 Edition. The warrants are based on either traffic volumes on both the major and minor streets or the number of crashes which would be mitigated by installation of all-way STOP control. Given the relatively low volume of traffic on the minor street (the Field Street approach from the east) and the absence of crashes, this intersection does not meet the warrants for an all-way STOP control. Given that the intersection was recently reconstructed as part of a major capital project, it would also not be a priority candidate for the additional major construction that would be required to install a raised intersection or other physical infrastructure changes. Should we continue to hear concerns about conflicts between drivers turning from Garden Street to Alpine Street conflicting with eastbound Field Street traffic, one option would be to consider reversing the direction of Alpine Street in order to eliminate the potential conflict. However, given the impact this would have on circulation for local residents, this decision would require additional community discussion and analysis of any unintended consequences that might result from such a change (i.e., new cut through traffic). Given the lack of crashes and the potential impact on neighborhood residents, we do not recommend any changes to this intersection at this time, but we will continue to monitor safety statistics and community concerns. Figure 6 - After Reconstruction Figure 5 - Before Reconstruction