A report on the feasibility and cost of installing computerized traffic signals along the City's main corridors

This memo is in response to Order #2 from the June 19th, 2017 City Council Meeting (Awaiting Report 17-50) requesting that we report back to the City Council regarding the feasibility and cost of installing computerized traffic signals along the city’s main corridors.

Cambridge has been working for many years to deploy a modern traffic signal control system, and has made substantial progress in a number of areas. Nonetheless, there are still significant upgrades and improvements needed to keep pace with the state-of-the-art while supporting the City’s overall transportation, safety, mobility, and sustainability goals. As noted in our Traffic Control Signal Policy1:

Our primary goal is to increase the public safety of our transportation facilities. The city’s transportation infrastructure is a scarce resource that we must allocate among a variety of needs and demands. It is our responsibility to make those allocations in a fair and equitable manner. We must balance the needs of all modes of transportation: vehicles, pedestrians, bicycles and transit.

As we strive to prioritize sustainable transportation modes, we operate our signal system in a manner consistent with that goal, particularly in terms of prioritizing the needs of pedestrians moving around the city (especially those with disabilities).

In considering computerized upgrades to the City’s traffic signal system, these upgrades can generally be broken down into three categories: 1. Installation of computerized traffic signal controllers, which are currently in place at all locations along our main traffic corridors, such as Massachusetts Avenue, Cambridge Street, Main Street, Broadway, and others. However, these signals currently operate in an isolated manner, without the ability to communicate outside their specific location. 2. Creation of communications links between signal controllers and a central control center and/or amongst each other. The Traffic, Parking, and Transportation Department is currently engaged in the deployment of new signal communications technology, initially in support of the Participatory 1 http://www.cambridgema.gov/~/media/Files/Traffic/official-Signal-Policy.pdf Page 2 of 3 Budgeting item for Better, Faster #1 Bus, which is intended to provide reliability and speed improvements for buses traveling along the Massachusetts Avenue corridor. This updated technology will ultimately include wireless communications from the City Hall Annex (344 Broadway) to 15 signals on Broadway, Prospect Street, and Massachusetts Avenue. These communications links will allow the Department to achieve central computerized control of the traffic signals within that specific network. While these improvements are being implemented with the goal of allowing buses to request a priority green signal indication to reduce travel time and improve reliability, it will also provide opportunities for improved management of traffic operations and reduced downtime due to equipment failures. This technology could also be used to implement a “green wave” signal progression, but at speeds optimized for cyclists and/or to encourage lower speed driving. Our intent is to expand this type of communication to other signals on the main corridors, using this initial network as a template. In these future deployments, we expect to use a range of communications technologies to reach the signal controllers, including fiber optic cables, wireless microwave transmitters, wifi, and cellular networks. 3. Supportive technology upgrades that take advantage of the first two categories of improvements.

Additional technology improvements that should be considered as part of a signal modernization program to better manage traffic congestion include multi-modal video detection and upgraded signal controller units that provide for adaptive traffic signal control. These will allow the system to become more dynamic, including features such as automatically changing the signal timing program to a peak-period timing plan during off-peak hours in response to changes in volume along a corridor due to events, detours, or incidents in the roadway network. Fully dynamic, traffic responsive signal timing is not feasible for our urban roadway network, since that would conflict with our efforts to prioritize pedestrian safety and accessibility. Cities which have implemented fully dynamic signal timing have found that these changes have significant negative impact to pedestrian delay, causing reduced compliance and potential related safety concerns. Although there is less experience with the impacts on bicycle safety and operations, it is reasonable to expect that similar concerns would exist for that group of users. As a result, we are aiming to develop a system that is as responsive as possible to all users, while continuing to prioritize safety and mobility for sustainable modes and vulnerable road users. To begin to develop experience with these technologies, we are currently conducting a three-month test of a Gridsmart video detection system2 at the intersection of Garden Street, Sherman Street, and Huron Avenue. This system is only capable of detecting the presence of motor vehicles, pedestrians, and bicycles, and actuating the traffic signal in response to those users, and does not record any video data or provide any live video feed externally.

The Department’s goal is to work over a five-year period to expand the network of connected signals to most major corridors in Cambridge while using existing network infrastructure wherever possible. The cost of these improvements on a per location basis varies depending on the condition of the existing equipment, proximity to adjacent signals for communications, and the need for additional technology such as video detection. The expected range of costs is between $5,000 and $40,000 per intersection. We are currently in the process of developing a more detailed and organized capital program for our signal system, which will provide a more detailed and specific assessment of our technology needs and the associated costs. 2 https://gridsmart.com/ Page 3 of 3 This Policy Order also included a request to assess the potential for CO2 reductions, safety improvements, and congestion management that might be associated with this type of system. Although this type of analysis is possible, experience has shown that these types of assessments tend to overvalue the short-term congestion reduction benefits associated with operational improvements, while not accounting for the long-term increases in driving that these operational improvements may generate (so- called “induced demand”). Although we clearly want to make our streets operate as efficiently and smoothly as possible, we do not want these improvements for motor vehicle traffic to come at the expense of safety and comfort for sustainable transportation modes. In the long term, we believe that the strategies that will lead to the most successful transportation system are those that reduce the attractiveness of driving by slowing vehicular speeds, prioritizing walking, cycling, and transit, and preserving space for truck loading and emergency vehicle access. Upgrades to our traffic signal system are clearly an element of many of these strategies, and will be key to achieving our long-term safety, environmental, and mobility goals.