Chapter 7 Transit Signal Priority Treatment Plan Evaluation of Transit Signal Priority Transit signal priority (TSP) allows transit vehicles to progress through at signalized intersections. While there are many means for implementing TSP, the common element is that the traffic signal controller reacts to the presence of an approaching bus and allows the bus to pass through the intersection sooner than would have occurred otherwise. Typically, this is done by extending the green light for several seconds to allow the bus more time to pass through the intersection. Bus stops are generally located at or near intersections, typically on the far side of intersections when local conditions permit. TSP measures that extend a green light are ineffective at intersections with near-side bus stops. If a near-side bus stop is necessary, then the TSP for that approach should be disabled, or a different TSP measure should be used (for example, starting the green phase a few seconds early). The proposed BRT route in the Showcase Corridor can be divided into four segments: downtown, Park Boulevard, El Cajon Boulevard, and College Avenue. In the downtown area, adjustments to the signal phase splits are likely to be minimal. Therefore, trying to apply transit priority in the downtown area would likely be unproductive and not worth the effort and expense. Along College Avenue, there is only one signalized intersection—at the north end of the corridor near the campus. With only one signalized intersection, the benefits of TSP would be small, but worth pursuing. Along Park Boulevard, side street traffic volumes are relatively light, so the traffic signals grant a large portion of the cycle length to the north-south traffic on Park Boulevard. Because of this, the benefits of implementing TSP on Park Boulevard are presumed to be low. Also, with the exception of the University and El Cajon intersections, most the traffic signals along Park Boulevard are not currently connected to the city's QuicNet/4 signal system, and there is no near-term plan to make that connection. Of the four segments of the proposed BRT route, El Cajon Boulevard offers the greatest potential for successful implementation of TSP. There are a large number of traffic signals along El Cajon. In some areas, there is a signal at every second cross street, and thus the frequency of signal-related stops is high. And because about one-quarter of the cross streets are minor arterials with relatively high traffic volumes, there is generally much longer cross-street green time. West of 43rd Street, El Cajon Boulevard is very wide (six travel lanes, with parking lanes in most sections and medians with left-turn lanes). Pedestrian crossing times allocated to the cross streets increase the side street time to nearly half the cycle length. Signal coordination is in effect only during the morning, noon, and afternoon peak periods, so TSP might be deployed during both coordinated and free-flow operation. Kimley-Horn and Associates, Inc. 7-1 April 2005 Opticom pre-emption equipment is already in place at many of the signalized intersections along El Cajon Boulevard. However, this equipment is outdated and not capable of transit priority call detection. If an Opticom-based TSP system is installed, the existing Opticom equipment will have to be upgraded at all the intersections where TSP is to be provided. The City of San Diego's QuickNet/4 traffic signal system controls or manages traffic signals in downtown San Diego, as well as a selected subset of the city's arterials. The limiting factor for arterials to be monitored by the traffic signal system is the absence of interconnect cable between the arterials and the city's downtown traffic management center, where the signal system resides. Many of the city's signals are not hardwired into the signal system, and there is no program planned for bringing the isolated streets into the signal system by constructing new communication linkages. Along the Showcase Corridor, most of Park Boulevard is not on the system, but all of El Cajon Boulevard is interconnected. A fiber-optic communication system is in place for the entire length of El Cajon Boulevard, and communication hubs exist at several locations. The San Diego traffic engineering division is currently evaluating a possible wireless communication linkage for suitability and performance on the QuicNet/4 system. The Ricochet network was deployed in San Diego several years ago, but then ceased operation when the company went bankrupt. The Ricochet facilities and service are now being resurrected, and San Diego is one of the initial efforts in this system restart. If this proves a successful method for providing signal system communications, the city may have a relatively inexpensive method for expanding signal system coverage. Lacking this wireless deployment, it is likely that the city's many fully actuated signals will not have central supervision or control for the foreseeable future, which could be an important factor in implementing TSP along the Showcase Corridor. Agency Characteristics and Preferences City of San Diego The City of San Diego has already successfully employed several queue-jump operations at downtown San Diego intersections to provide an advantage to transit. Thus, the city would likely support a replication of this strategy along the Showcase Corridor. The traffic engineering division would support TSP, with the assumption that the frequency of priority grants would not exceed approximately every 10 to 15 minutes. However, the city's traffic engineering division requested that where opposing direction BRT vehicles meet, the successive requests for transit priority at a single intersection may not be granted. The city's other main TSP considerations include the need to minimize added operations and maintenance efforts that may develop as a result of TSP deployment, the need to have TSP system records and reports on activity, and the need to maintain reasonable traffic flow. Caltrans Along El Cajon Boulevard in the Showcase Corridor, there are signalized intersections under the jurisdiction of Caltrans (I-805 and I-15 interchanges). These signals warrant the involvement of Caltrans to ensure coordinated timing along the corridor. The focus will be on signal timing, since Caltrans has no plans to implement TSP now or in the near future in the Showcase Corridor area. However, Caltrans would be willing to evaluate use of TSP in this area. In the Oakland area, Caltrans recently implemented its first TSP system. Based on their analysis and results, TSP at Caltrans signals in the Showcase Corridor may be possible in the future. Kimley-Horn and Associates, Inc. 7-2 April 2005 If TSP is deployed at Caltrans signals, the agency's preferences include: ƒ ƒ ƒ ƒ ƒ ƒ Maintain the ability to monitor signals Maintain integrity of the central system and communications to the controller Prefer loop independence due to reliability issues Suggest regional technology choice for ease of maintenance Recommend that not every bus be granted TSP, only BRT buses Grant TSP no more than once every three cycles SANDAG/MTDB The information technology (IT) department of SANDAG/MTDB is an important partner in the Showcase Project because of its involvement with and procurement of on-board vehicle technology and a central transit management system. One operational consideration from the SANDAG/MTDB perspective is to grant TSP only if a BRT vehicle is late or to maintain consistent headways. SANDAG/MTDB IT has received many regional requests for transit data. As all regional transportation systems will eventually be moving to the San Diego Joint Transportation Operations Center (J-TOC), SANDAG/MTDB will wait until the J-TOC needs/ requirements have been established to determine how best to handle data management and TSP data reporting. Evaluation Criteria Numerous technologies exist for implementing TSP. These technologies are widely varied,1 and no one solution is an obvious best choice. Every potential TSP approach has some positive characteristics for the Showcase Project—and some drawbacks. Therefore, an evaluation matrix was created to weigh the potential solutions against a set of criteria, presented below. Using these criteria, the 13 types of TSP technologies were evaluated in a matrix format (see Table 71). A. B. C. D. E. F. G. H. I. J. K. L. Is line of sight required or not? Does the technology add any significant communication system loading? Is the technology proven; are there other deployments? Will a single point of failure produce a low level of risk for failure of the rest of the system? Can the standard system be deployed with little customization required? Where is equipment required for the typical deployment? (i.e. on the bus, in the field, or both, and how much equipment is needed) Is the TSP programming highly flexible for the owner? Is a low level of effort needed to maintain this solution? Will system deployment incur traffic disruption? Will this deployment be easy and/or quick? Does the system have a next generation possibility? Can operational data be extracted? 1 The Transit First Downtown-to-SDSU Show Case Project transit priority report, prepared by Meyer, Mohaddes Associates in May 2004, evaluated 13 different types of technology available for implementing TSP. Kimley-Horn and Associates, Inc. 7-3 April 2005 Table 7-1: Insert 11 x 17 matrix table (Table 1 from the MMA May 2004 report) Kimley-Horn and Associates, Inc. 7-4 April 2005 Based on the evaluation matrix shown in Table 7-1, the list of 13 technology types was compared and contrasted to eliminate those with significant negative attributes. The resulting list of five TSP solutions was evaluated further based on initial costs, recurring costs, interface and control, operational characteristics, maintenance considerations, and combined costs. Recommended TSP Solution Taking into account the many factors used in the TSP evaluation, the following are the TSP recommendations for the Showcase Project: 1. Upgrade the Opticom systems along El Cajon Boulevard to the latest models (750 series phase discriminators and 720 series detectors). 2. Equip the Showcase Project BRT buses with encoded Opticom emitters (model 792T) controlled by the on-board IVCU. 3. Upgrade the controller firmware in the 29 El Cajon Boulevard Type 170 controllers from 223sd4 to 233. 4. Consider the deployment of the BI Tran-based TSP solution as a parallel function solely for comparison testing purposes. 5. Consider equipping some or all of the 29 El Cajon Boulevard intersections with the TrafficWerks data mining service (capture and analysis of actual operational data). The recommended TSP solution is a mature and widely installed system, with the following attributes: • Known deployment costs • Reasonably low ongoing operation and maintenance costs • Unquestioned efficacy • Reasonable capital cost • Low risk of failure of one intersection damaging the network Making the incremental upgrade to the region's existing Opticom system will not require a long lead time, and it will also not require substantial immediate retrofit costs for the city's emergency vehicle fleet. The next generation Opticom GPS system has significant appeal, but it is a new system and could easily be subject to substantial improvements over the next few years as lessons are learned from its early installations. However, prior to selecting Opticom over Opticom GPS, it would be prudent to explore whether the San Diego Fire-Rescue Department will retain a longterm commitment to Opticom (as opposed to switching to Opticom GPS). The region's current Opticom system is well-aged, and a significant investment will likely be required either way. Either Opticom or Opticom GPS can effectively provide TSP; the choice between the two would likely lie with the long-term plans of the fire department. Kimley-Horn and Associates, Inc. 7-5 April 2005 Deployment of TSP Implementing TSP can be complex, and it is recommended that the system be deployed in phases to match the funding stream envisioned for the project. Since the new BRT service will not start immediately, there is time to incrementally deploy the non-bus elements of the recommended TSP solution. Some of the tasks that could be accomplished before the BRT service begins are outlined below. Detailed design is the first step to be accomplished after selecting the preferred TSP solution. Depending on the choice, this could be as simple as preparing requisition documents and specifications. Preparing a deployment schedule to match the anticipated funding stream would be the next step. With the detailed design under way, more exact budget estimates will be available to feed into the deployment schedule. In terms of field deployment, upgrading the Type 170 controller software would be a logical first step. Achieving both queue jump and TSP in a single software program is recommended prior to upgrading any field intersections. This could probably be included as an element of the Regional Arterial Management System (RAMS) project. Upgrading the intersection Opticom equipment could also be started as soon as the decision is made about which system to employ. Improvements to these infrastructure items would be beneficial to the fire department, so there is no need to delay their deployment until the BRT service begins operation. Pilot Program Several regular fixed-route buses along El Cajon Boulevard could be fitted with an encoded Opticom emitter, and one or two key intersections could be equipped with updated Opticom hardware as a pilot program. This limited deployment could be monitored for: a. Proper operation of the equipment b. Reception of the TSP call at the controller c. Proper response by the controller to the priority request d. Benefit to the bus/transit system The lessons learned from this limited deployment could benefit deployment of the corridor system. This approach has been used by other transit systems to evaluate a TSP system before system-wide deployment. Regional Issues Implementing TSP in the El Cajon Boulevard corridor will be an element in determining whether, when, where, and with what technology TSP will be used in other transit corridors in the region. If the TSP system chosen for the Showcase Project is successful, it should be considered as the choice for the remainder of the region. However, the other cities in the region will have to be able to bring their signalized intersections into the overall system. The signal system communication infrastructure will be the most significant impediment to regional implementation of TSP. Kimley-Horn and Associates, Inc. 7-6 April 2005 San Diego's current signal system, a BI Tran QuicNet/4 system, will remain in place. The new RAMS project proposes to standardize on a new BI Tran signal system product (QuicNet/5) across most San Diego County cities, so as to facilitate the sharing of system information, coordination timing plans, and other system data. If the BI Tran-based TSP solution proves to be successful on El Cajon Boulevard, then it should be given strong consideration as the system for the remainder of the region. However, the cities in the region will have to be able to bring signalized intersections along these major corridors onto the BI Tran system, so as to be able to issue priority commands from the system to targeted intersections. The signal system communication infrastructure will be the most significant impediment to this TSP solution. Otherwise, the Opticom™ (or Opticom™ GPS) system will be the de facto solution for providing transit priority in the future. Kimley-Horn and Associates, Inc. 7-7 April 2005