Bus Signal Priority in Santa Clara County, California
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BUS SIGNAL PRIORITY IN SANTA CLARA COUNTY, CALIFORNIA James T. Jarzab Principal, Commuter Associates P.O. Box 5293 Pleasanton, CA 94566 USA 925-895-5559, [email protected] Paul Chiu (Senior Transportation Electrical Engineer, [email protected]), James Lau (Transportation Electrical Engineer, [email protected]), and David Man (Transportation Electrical Engineer, [email protected]) Caltrans District 4 111 Grand Ave Oakland, CA 94612 510-286-4444 Casey Emoto (Deputy Director, [email protected] ), David Kobayashi (Senior Transportation Planner, [email protected] ), and Shanthi Ganji (Assistant Transportation Engineer, [email protected] ) VTA 3331 N. First Street San Jose, CA, 95134-1906 408-321-2300 Ho Nguyen Project Manager, San Jose DOT 200 E. Santa Clara Street San Jose, CA 95113 408-535-3850, [email protected] Karthik Swamy Senior Transportation Planner AC Transit 1600 Franklin Street Oakland, CA 94612 510-891-4735, [email protected] Bus Signal Priority in Santa Clara County, California ABSTRACT The paper provides background for and analysis of bus signal priority applications used by the Valley Transportation Authority (VTA) along route 522, a rapid bus route. Technical features of the application are discussed, and the functional benefits of the technologies are calculated. The paper addresses two technology types—loop and gps/spread spectrum—and discusses the operational constants under which these technologies are applied. KEY WORDS Bus, signal, priority, controller, loop, GPS, VTA, traffic, San Jose, Santa Clara OVERVIEW The purpose of this evaluation is to assess the increase in average operating speed provided by the Intelligent Transportation System (ITS) application of bus signal priority (BSP) in rapid bus operation as compared to traditional local bus operation. Measurement of technology performance was provided independently by an Automatic Vehicle Location/Automatic Vehicle Identification (AVL/AVI) equipment package that identifies and records vehicle location precisely at any given time with Global Positioning Satellite capabilities; data are logged electronically, analyzed and stored independent of the BSP operation. Also an ITS application, the AVL/AVI system is used to monitor and manage transit fleet operations. The VTA Rapid 522--in operation since July 2005--has provided an opportunity for the implementation and evaluation of two BSP technologies. Designed to provide high quality public transit in a mixed traffic environment, the service relies heavily on automatic vehicle identification and location technology for signal priority, system management and real-time passenger information; the project also incorporates queue jump lanes for improved operations and minor station enhancements. While serving six municipalities, highway operations along the rapid bus route are controlled primarily by Caltrans and the City of San Jose. No significant land acquisition has been required in project implementation. From the standpoint of environmental regulation this project is essentially categorically exempt. The 27 mile long Line 522 BRT project has unofficially been subdivided into three zones for funding and project management purposes: Zone I is the 6.2 mile segment of El Camino Real, the limits extending along ECR approximately from the Palo Alto Transit Center to Castro St. in Mountain View; Zone II extends from Castro St. to Race Street in -1- Bus Signal Priority in Santa Clara County, California San Jose, essentially the limits of Caltrans’ jurisdiction along State Route 82; and, Zone III extends east of Race St. for the remaining length of Line 522 along The Alameda, Santa Clara Street and Alum Rock and then south along Capitol. Note that this alignment reflects an authorized modification from the original project proposal necessitated by service restructuring. Line 22, the primary local route in the corridor, and Line 522 Rapid Bus run a combined headway of approximately eight minutes during weekday peak periods and carry approximately 20% of VTA’s daily riders. Figure 1 Initial Project Corridor For a variety of reasons—including technology incompatibilities and competing priority systems of light rail transit—not all signals in the corridor are equipped to provide bus signal priority. Furthermore, while signal priority enables the operation of rapid bus service with reduced stops and more liberal operating rules than local service, it is not solely responsible for the reduction of travel time herein reported. Buses receiving priority in Zone I and Zone II travel 18.4% faster than those without priority; these vehicles are aided by loop-enabled technology. Those receiving priority in Zone III using GPS enabled technology travel 23.0% faster than those without priority. Average daily customer demand in the corridor has increased an average of 5.4% over pre-project levels in the prior twelve months; this percentage is down from initial service performance, -2- Bus Signal Priority in Santa Clara County, California possibly due to general economic malaise. Traffic conditions in the corridor as measured by intersection level of service have worsened since project initiation and VTA’s system was significantly altered in January 2008, making multi-period comparisons somewhat problematic. Note that most signals in all zones are interconnected and coordinated. PROJECT LIMITS AND SCOPE The operating characteristics of the signal priority implementation of both Zone I and Zone II are analyzed as a single unit. These areas are identified on the map in Figure 1, highlighted in blue and green and representing Zone I and Zone II, respectively. (Note that “Zone” and “Phase” are used interchangeably, as “Phase” is a legacy of the project funding structure.) Improvements in the respective segments are similar in that they focus almost exclusively on traffic signal system components (e.g. controllers, priority detection equipment, master traffic management software, etc.); however, two queue jump lanes are found in Zone I. While it is presumed that the queue jump lanes generate some of the time saving identified in the accompanying travel time analysis, available data used in this evaluation does not allow conclusive determination. Figure 2 Controller and Detector Loop Bus Signal Priority Equipment -3- Bus Signal Priority in Santa Clara County, California Following the initial pilot implementation of BSP at the westernmost limits of El Camino Real, a subsequent expansion involved upgrading traffic signal controllers along El Camino Real in Mountain View, Sunnyvale and short stretch of The Alameda in the City of San Jose. The limits of this section (Zone II) are depicted in green on Figure 1. Existing advance detector loops—usually less than 300 feet before the intersection in the number 2 and number 3 lane—and stop bar loops are equipped with dual function detector cards that identify the approach of a bus eligible for priority. The traffic controller software assesses the approach of an eligible bus as a request and: a) provides an early green and green extension, or b) does nothing, which occurs if the bus is expected to clear the intersection in an unaltered signal cycle, priority was provided in the immediately prior signal cycle, a pedestrian call was initiated, a emergency vehicle preemption request was received or the traffic controller is out of coordination. Priority calls are placed first come/first served. Besides providing priority detection equipment, the City of San Jose’s master signal control system required enhancement in order to handle bus signal priority requests. Pavement detector loop-equipped priority request generation transmitters and receivers (Figure 2) were also procured. Traffic control system incompatibilities with equipment operated by the City of Santa Clara prevented implementation within the City’s jurisdiction; however, the City of Santa Clara has remained cooperative and continues to explore opportunities for bus signal priority implementation at a later date. Traffic controller information for the entire Line 522 operating limit is provided in Appendix B. Figure 3 GPS/Spread Spectrum Bus Signal Priority Transceiver (Bus) -4- Bus Signal Priority in Santa Clara County, California A third implementation involves upgrading traffic signal controllers and related system components along The Alameda, Santa Clara Street and Alum Rock Avenue in order allow provision of bus transit priority (Zone III), depicted in Figure 1 in yellow, including an uncolored segment of Alum Rock Avenue between King and Capitol. GPS/Spread Spectrum priority request generation equipment using vehicle mounted transceivers (Figure 3) and traffic cabinet mounted receivers (Figures 4) were also procured. Note that bus signal priority is not provided in the vicinity of First and Second Streets in downtown and along South Capitol Avenue in San Jose due to possible conflicts with light rail priority applications. The project limits were altered slightly from an original proposed routing due to the restructuring of the rapid bus service, eliminating improvements along King Road and including improvements along Alum Rock Avenue. Figure 4 GPS/Spread Spectrum Bus Signal Priority Transceiver (Controller) In this zone, bus detection is achieved through GPS detection. The GPS/Spread Spectrum system is configured to place a priority call as a bus is detected leaving the previous signalized intersection or 1000 feet in advance of the target intersection, whichever is less. The system