ITS Transit Standards Professional Capacity Building Program
Module 8: Arterial Management and Transit Signal Priority: Understanding User Needs for Signal Control Priority (SCP) Based on NTCIP 1211 Standard, Part 1 of 2
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Module 8: Arterial Management and Transit Signal Priority: Understanding User Needs for Signal Control Priority (SCP) Based on NTCIP 1211 Standard, Part 1 of 2
Table of Contents
Introduction/Purpose - 2
Samples/Examples - 3
Reference to Other Standards - 4
Case Studies - 4
Glossary - 5
References - 7
Study Questions - 7
Module Description
This module is an introduction to Intelligent Transportation Systems (ITS) Transit Standards for improving transit service along arterials, with a focus on transit signal priority. Modules 1 to 3 are recommended prerequisites for participants and are, respectively, Introduction to ITS Transit Standards; Transit Management Standards, Part 1 of 2; and Transit Communications Interface Profiles (TCIP) Part 1 of 2.
The logical next step for the participant after taking this module is Module 9: Arterial Management and Transit Signal Priority: Specifying Requirements for Signal Control Priority (SCP) Based on NTCIP 1211 Standard, Part 2 of 2.
1. Introduction/Purpose
Transit managers are looking at transit signal priority as a potential tool to improve schedule adherence, improve transit vehicle efficiency, make transit service more reliable, and improve transit vehicle travel times with minimal negative impacts to normal traffic operations. Signal Control Priority (SCP), which transit signal priority (TSP) is a subset of, is an operational strategy that provides preferential treatment (priority) to facilitate the movement of fleet vehicles such as transit, emergency service, and commercial fleets, through signalized intersections.
This module (Arterial Management and Transit Signal Priority: Understanding User Needs for Signal Control Priority (SCP) Based on the NTCIP 1211 Standard) is the first of a two-module set in arterial management. This module will introduce participants to the benefits of an SCP system, describe the components that may make up an SCP system, and provide an overview of how to identify and use applicable ITS standards to procure and operate an SCP system. This module also helps participants understand the scope of applicable ITS standards and assists in identifying the user needs of an SCP system. Although the discussion in the module will be for an SCP system in general, the focus will be on transit signal priority (TSP), which is a subset of SCP.
This module will also provide an example case study, demonstrating how a transit agency might work with a traffic signal department to select an architecture for an SCP system, determine the features to be included in the SCP system, and how to develop a procurement specification.
The second module of the two module-set on arterial management (Arterial Management and Transit Signal Priority: Specifying Requirements for Signal Control Priority (SCP) Based on NTCIP 1211 Standard) focuses on using the ITS standards to develop project specifications for procuring an SCP system.
2. Samples/Examples
The following is a complete list of the user needs identified in NTCIP 1211 v02.
2.4 Architectural Needs
2.4.1 Integral Entities
2.4.2 Provide Live Data
2.4.3 Support Multiple Instances of an Entity
2.4.4 Compressed Data
2.4.4.1 Provide Compressed Data between a Management Station and a PRS
2.4.4.2 Provide Compressed Data between a Management Station and a CO
2.5 Features
2.5.1 Interface - Management Station to PRS
2.5.1.1 Manage the PRS
2.5.1.1.1 Determine PRS Identity
2.5.1.1.2 Determine PRS Configuration
2.5.1.1.3 Configure Reservice Period
2.5.1.1.4 Configure Time to Live Period
2.5.1.1.5 PRS Clock Synchronization
2.5.1.2 Determine Priority Request Criteria
2.5.1.3 Monitor the PRS
2.5.1.4 Retrieve Log Data from the PRS
2.5.2 Interface - Management Station to CO
2.5.2.1 Configure Priority Strategies
2.5.2.2 Determine Priority Strategies
2.5.2.3 Monitor the CO
2.5.2.4 Retrieve Log Data from the CO
2.5.3 Interface - PRG to PRS
2.5.3.1 Exchange Priority Requests
2.5.3.2 Exchange Priority Request Status
2.5.4 Interface - PRS to CO
2.5.4.1 Exchange Service Requests
2.5.4.2 Exchange Service Request Status
2.5.5 Backward Compatibility Need
2.5.5.1 Backward Compatible with NTCIP 1211 v01
3. Reference to Other Standards
4. Case Studies
Actual case studies can be found in Transit Signal Priority (TSP): A Planning and Implementation Handbook: ITS America, May 2005. https://nacto.org/docs/usdg/transit_signal_priority_handbook_smith.pdf
5. Glossary
| Term | Definition |
|---|---|
| AASHTO | American Association of State Highway and Transportation Officials. |
| APTA | American Public Transportation Association |
| CAD/AVL | Computer Aided Dispatching/Automatic Vehicle Location |
| CO | Coordinator |
| Concept of Operations | A document that describes the purpose for a system project, including a description of the current and proposed system, as well as key user needs that the new system is required to address. |
| Coordinator | A logical device or program/routine that provides coordination. An integral part of a Traffic Signal Controller. |
| ICM | Integrated Corridor Management |
| ITE | Institute of Transportation Engineers |
| ITS | Intelligent Transportation Systems |
| Management Station | Defined as a computing platform that manages NTCIP field components, such as a PRS or a CO. A management station may be a traffic management center or a maintenance laptop that a field technician may use on a trip to visit the component. |
| NEMA | National Electric Manufacturers Association |
| NTCIP | National Transportation Communications for ITS Protocol |
| Preemption | Per NTCIP 1202:2005, the transfer of the normal control (operation) of traffic signals to a special signal control mode for the purpose of servicing railroad crossings, emergency vehicle passage, mass transit vehicle passage, and other special tasks, the control of which requires terminating normal traffic control to provide the service needs of the special task. |
| Priority | The preferential treatment of one vehicle class (such as a transit vehicle, emergency service vehicle or a commercial fleet vehicle) over another vehicle class at a signalized intersection without causing the traffic signal controllers to drop from coordinated operations. Note: Priority may be accomplished by a number of methods including changing the beginning and end times of greens on identified phases, changing the phase sequence, or inclusion of special phases, without interrupting the general timing relationship between specific green indications at adjacent intersections. |
| Priority Request | The information that describes a need for priority service based upon user-defined criteria (such as the number of minutes behind schedule, vehicle occupancy levels, vehicle class, etc.). Note: A priority request is sent from a Priority Request Generator to a Priority Request Server (PRS). |
| Priority Request Generator (PRG) | A logical or physical entity that initiates a priority request. |
| Priority Request Server | A logical or physical entity that manages and prioritizes one or more service requests. |
| PTV-DAT | PTV-DATa manager. A logical entity on a public transit vehicle responsible for data management. |
| PTV-PRI | Public Transit Vehicle-PRIority. A logical entity on a public transit vehicle responsible for management transit signal priority functions, including the generation of priority requests. |
| Service Request | The information that describes a priority service to be processed by the Coordinator within a Traffic Signal Controller. Note: A service request is sent between a Priority Request Server and a Traffic Signal Controller. |
| Signal Control Priority (SCP) | An operational strategy that provides preferential treatment (priority) to facilitate the movement of fleet vehicles through signalized intersections. |
| TCIP | Transit Communications Interface Profiles |
| TMC | Traffic Management Center |
| TMDD | Traffic Management Data Dictionary |
| Transit Signal Priority (TSP) | A subset of Signal Control Priority focusing on transit fleet vehicles. |
6. References
Transit Signal Priority
Systems Engineering
7. Study Questions
1. How can SCP directly improve the attractiveness of transit to travelers?
2. Which of the following components determines which priority requests to service?
3. What is not a significant factor in selecting an architecture for an SCP System?
4. Which is not a benefit of using ITS Standards?
5. Which of the following user needs are not supported by NTCIP 1211 v02?
6. What do the ITS standards define?
7. Which of the following is NOT a characteristic of an ICM program?