Module 37 - A208

A208: Using the ATC 5401 Application Programming Interface Standard to Leverage ITS Infrastructures

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(Note: This document has been converted from the Student Supplement to 508-compliant HTML. The formatting has been adjusted for 508 compliance, but all the original text content is included, plus additional text descriptions for the images, photos and/or diagrams have been provided below.)

 

Cover image for A208: Using the ATC 5401 Application Programming Interface (API) Standard to Leverage ITS Infrastructures. Please see the Extended Text Description below.

(Extended Text Description: Large graphic cover page with dark blue background with the title in white letters "A208: Using the ATC 5401 Application Programming Interface (API) Standard to Leverage ITS Infrastructures." At the middle left is the "Standards ITS Training" logo with a white box and letters in blue and green. The words "Student Supplement" and "RITA Intelligent Transportation Systems Joint Program Office" in white lettering are directly underneath the logo. Three light blue lines move diagonally across the middle of the blue background.)

 

A208: Using the ATC 5401 Application Programming Interface Standard to Leverage ITS Infrastructures

 

Table of Contents

Introduction/Purpose - 2

Traffic Concepts - 2

ATC Concepts - 5

Glossary - 8

Reference to Other Standards - 11

References - 11

Study Questions - 12

 

1. Introduction/Purpose

A208: Using the ATC 5401 Application Programming Interface Standard to Leverage ITS Infrastructures is the third module in the Professional Capacity Building (PCB) program on using the Advanced Transportation Controller (ATC) standards. Module A208 identifies the features of the ATC 5401 Standard, it describes the API Software defined by the standard, describes how ATC 5401 works with other ITS standards, and helps users specify ATC equipment that includes API Software for procurements.

 

2. Traffic Concepts

Intersection Actuation - The extent at which an intersection is equipped for vehicle detection.

Figure 1. Diagram illustrating different types of actuation in an intersection. Please see the Extended Text Description below.

(Extended Text Description: This graphic consists of three graphics each representing a 4 way intersection. The intersection graphics are arranged such that two are evenly distributed across the page. The third intersection graphic is below the first two and aligned center on the page. Each graphic is depicted as two two-lane roads intersecting perpendicularly North/South and East/West in the shape of a cross (it is assumed that upward is north). There is a centerline on each road to differentiate the northbound lane from the southbound lane and the eastbound lane from the westbound lane. The area where the roads cross (center of the cross) is blank (no lines running through it). In the bottom graphic, the southbound, northbound, westbound, and eastbound approaches to the intersection contain rectangles extending across the width of the lane (total four lanes). The rectangles have one edge at the point where the blank center area begins and extends back into the lane about 1 ½ times their width. This graphic is labeled "Actuated." The graphic to the upper right has the rectangles on the southbound and northbound directions only. This graphic is labeled "Semi-Actuated." The graphic on the upper left does not contain any of the rectangles. This graphic is labeled "Non-Actuated.")

Graphics: Ralph W. Boaz

Figure 1. Diagram illustrating different types of actuation in an intersection.

 

Cycle - The time required for one complete revolution of the timing dial (old definition). One complete sequence of signal indications.

Interval - Any one of the several divisions of the time cycle during which signal indications do not change. Examples:

Phase - Any combination of traffic movements receiving right-of-way simultaneously during one or more intervals

Overlap - A traffic movement timed concurrently with one or more phases (parent phases). Typically, the yellow and red clearance timing of the overlap is equal to that of the phase terminating the overlap.

Standard Quad or 8-Phase Intersection. The odd numbered phases represent left turn movements. The even numbered phases represent though movements. Overlaps are indicated by the plus signs and indicate that the right arrow would appear during the timing of the two phases indicated. Example: The overlap 08 + 01 would be allowed during the timing of 08 and 01. No U-turns on left arrow allowed.

Figure 2. Diagram illustrating a Standard Quad or 8-Phase intersection. Please see the Extended Text Description below.

(Extended Text Description: This is a graphic representing of a 4 way intersection. It is depicted as two four-lane roads intersecting perpendicularly North/South and East/West in the shape of a large cross (it is assumed that upward is north). There is a center median about the same width as the lanes on each road to differentiate the northbound lanes from the southbound lanes and the eastbound lanes from the westbound lanes. On each side of the median are parallel dotted lines to identify the two lanes on each side. The area where the roads cross (center of the cross) is blank (no lines running through it). For each of the southbound, northbound, westbound, and eastbound approaches to the intersection, the center medians narrow to provide an additional left turn lane for each approach (total 4). The straight through lanes and adjacent left turn lanes on each approach are separated by a dotted line. Each approach has its lanes identified as described below:

)

Graphics: Ralph W. Boaz

Figure 2. Diagram illustrating a "Standard Quad" or 8-Phase intersection.

 

Ring - Consists of two or more sequentially timed and individually selected conflicting phases so arranged as to occur in an established order.

Barrier - A reference point in the preferred sequence of a multi-ring controller at which all rings are interlocked. Barriers assure there will be no concurrent selection and timing of conflicting phases for traffic movements in different rings. All rings cross the barrier simultaneously to select and time phases on the other side.

Concurrent Groups - All of the phases between two barriers. Typically, they are the left turn and through movements on a single street.

Dual Ring Operation for a Standard Quad - See diagram below. There are two rings. The first consists of phases 1-4 and the second consists of phases 5-8. A phase in Ring 1 can time with a phase in Ring 2 provided they are a part of the same concurrent group.

Figure 3. Diagram illustrating a Standard Quad or 8-Phase intersection. Please see the Extended Text Description below.

(Extended Text Description: This is a graphic representing the flow of service for each of the turning movements in a 4 way intersection. There are eight squares arranged in a two columns and four rows all evenly spaced. Above the left column of squares is a label "RING 1." Above the right column of squares is a label "RING 2." There is a dashed line extending vertically from between the labels to the bottom of the graphic. The dashed line is centered between the columns of squares. There is a horizontal dashed line extending across the graphic evenly between the second and third row of squares. The line is labeled "BARRIER." There is a second such dashed line and label extending across the graphic below the fourth row of squares. To the right of the graphic is a large right bracket highlighting the top four squares (above the first barrier line) with the label "CONCURRENT GROUP." To the right of the graphic is a large right bracket highlighting the bottom four squares (below the first barrier line) labeled "CONCURRENT GROUP."

Each square contains a number and an arrow. The left column of squares contains the following (top to bottom):

The right column of squares contains the following (top to bottom):

There are solid lines connecting the numbered squares as follows:

)

Graphics: Ralph W. Boaz

Figure 3. Diagram illustrating a "Standard Quad" or 8-Phase intersection.

 

3. ATC Concepts

Figure 4. Field architectures using Transportation Field Cabinet Systems (TFCSs) for Performing Traffic Management. Please see the Extended Text Description below.

(Extended Text Description: This is a graphic of 5x5 crisscrossing perpendicular lines representing a downtown "grid" of intersecting streets. The grid forms a 4x4 (rows and columns) representation of city blocks. In the bottom left side of each city block (except for the first block in the third row) is a TFCS (each TFCS is about 2/3 of the height of block. The leftmost TFCSs in row 3 and 4 have the abbreviation "FMS" above them (stands for Field Management Station). Left of the grid is a graphic of a building which represents a traffic management center (TMC).

The TFCSs are associated to different field architectures. Dotted lines are used to represent communications.

  1. The TFCSs in column 4 rows 1 and 2 have arrows pointing to them with a label to the right of the grid saying "Standalone TFCSs."
  2. There are dotted lines between the TMC and TFCSs in column 1 rows 1 and 2. The TFCSs have arrows pointing to them with a label above the grid saying "TFCSs Under Central Control."
  3. There are dotted lines between the four TFCSs in row 4 of the grid (note the leftmost is labeled FMS). This row of TFCSs has an arrow pointing to it with a label to the right of the grid saying "TFCSs in a Closed-Loop System."
  4. There is a dotted line between TMC and TFCS (labeled FMS) in column 2 row 3. There are dotted lines between the three TFCSs in row 3 of the grid. This row of TFCSs has an arrow pointing to it with a label to the right of the grid saying "Hybrid – TFCSs in a Closed-Loop System and Under Central Control."
  5. The four TFCSs in columns 1 and 2, rows 2 and 3, have dotted lines between them where each TFCS is connected to the other three. The TFCSs have an arrow pointing to them with a label above the grid saying "TFCSs in a Peer-to-Peer System."

)

Graphics: Ralph W. Boaz

Figure 4. Field architectures using Transportation Field Cabinet Systems (TFCSs) for Performing Traffic Management.

 

Figure 5. Evolution of Transportation Control Equipment. Please see the Extended Text Description below.

(Extended Text Description: This graphic contains a horizontal arrow that stretches almost the entire width of the graphic at the bottom. There are years listed beneath the timeline (not evenly spaced) as follows: "1940s," "1976," "1980s," "1992," "1998," and "2006." Above the timeline are labeled photographs of TFCSs of different shapes and sizes as follows:

  1. Above the 1940s point in the time line is a picture of a TFCS that is about 3 1/2 feet tall and 2 feet wide with the door open and out of view. It has a single shelf approximately 1/3 down from the top of the cabinet. On the shelf is a cuboid type taller than it is wide with a dial on it. Otherwise the internal back of the cabinet has an electrical panel with numerous wires attached to it. The label above this picture says "Electro-Mechanical."
  2. Above the 1976 point in the time line is a picture of a TFCS that is about 4 feet tall and 2 1/2 feet wide with the door open and out of view. It has two shelves approximately 1/3 and 2/3 down from the top of the cabinet. On the top shelf sit two cuboid electronic devices. On the middle shelf is a larger cuboid device about 1 1/2 feet wide with four thick round cables attached to it. There is an additional smaller cable coming from the device. All 5 cables are attached and spaced equidistantly across the bottom portion of the device. The lower internal back area of the cabinet has an electrical panel with numerous wires attached to it. The label above this picture says "NEMA TS 1."
  3. Above the 1980s point in the time line is a picture of a TFCS that is about 5 1/2 feet tall and 2 feet wide with the door open and out of view. The interior of the cabinet contains a 19 inch wide standard electronic equipment rack. The side metal rails of the rack run along the left and right sides of the front of the cabinet interior. There are four sections of the equipment that extend edge to edge of the cabinet interior attaching to the side rails of the rack with screws. There are a few thin cables running between components. There is a piece of cardboard in over the left side of the upper section of the cabinet. The label above this picture says "Model 3XX."
  4. Above the 1992 point in the time line is a picture of a TFCS that is about 4 1/2 feet tall and 3 1/2 feet wide with the door open and out of view. It has two shelves approximately 1/6 and 2/5 down from the top of the cabinet. On the top shelf sit two cuboid electronic devices that are racks for holding other devices. On the middle shelf are two larger cuboid devices with one being about 1 1/2 feet long and 1 foot high and the other about 1/2 feet wide and 1 foot tall. There are cables running between all of the devices. The lower remainder of the cabinet has various devices with lights on them that are plugged into an electrical panel in the back of the cabinet interior. The label above this picture says "NEMA TS 2."
  5. Above the 1998 point in the time line is a picture of a TFCS that is about 4 1/2 feet tall and 3 1/2 feet wide with the door open and out of view. It has two shelves approximately 1/6 and 2/5 down from the top of the cabinet. On the top shelf sit two cuboid electronic devices that are racks for holding other devices. On the middle shelf are two larger cuboid devices with one being about 1 1/2 feet long and 1 foot high and the other about ½ feet wide and 1 foot tall. There are cables running between all of the devices. The lower remainder of the cabinet has various devices with lights on them that are plugged into an electrical panel in the back of the cabinet interior. The label above this picture says "TS 2 with NTCIP."
  6. Above the 2002 point in the time line is a picture of a TFCS that is about 4 feet tall and 2 feet wide with the outer metal shell of the cabinet removed exposing the interior of the cabinet. The interior of the cabinet contains a 19 inch wide standard electronic equipment rack. The side metal rails of the rack run along the left and right sides of the front of the cabinet interior. There are five sections of the equipment that extend edge to edge of the cabinet interior attaching to the side rails of the rack with screws. There are a few thin cables running between components towards the bottom of the cabinet. The label above this picture says "ITS Cabinet."

)

Graphics: Ralph W. Boaz

Figure 5. Evolution of Transportation Control Equipment.

 

Figure 6. Basic TFCS components. Please see the Extended Text Description below.

(Extended Text Description: This graphic illustrates that the field cabinet contains various equipment. There are two large graphics. The leftmost graphic is the aluminum looking cabinet. The cabinet has a door with a horizontal handle on the left side of the cabinet and two vent slots in the center top. The cabinet is about 2.5 times high as it is tall. Above it is the label "Housing." The graphic on the right is about twice the size of the cabinet on the left. It is an enlargement of the aluminum cabinet without a door and showing the contents of the cabinet. Inside the cabinet are six labeled cuboids that extend almost the width of the cabinet. They are evenly distributed vertically. Starting from the top the cuboids are labeled "Input," "Controller," "Outputs," "Monitoring," "Power Supply," and "Internal Bus." There is a large left bracket between the cabinet graphic on the left and the enlarged cabinet on the right emphasizing that the right graphic represents the contents of the cabinet on the left.)

Graphics: Ralph W. Boa

Figure 6. Basic TFCS components.

 

Figure 7. Basic TFCS Operation. Please see the Extended Text Description below.

(Extended Text Description: On the upper right side of this graphic is the intersection graphic labeled "Actuated" as described in Section 2 Definition of "Intersection Actuation." In this case, the graphic is labeled "Field Sensors." In the lower right of the graphic is a graphic of a traffic signal mast arm. On the mast are three traffic signal heads. This graphic is labeled "Field Displays." On the left side of the graphic are four cuboids each the same size and about 5 times wider than their height or depth. They are evenly spaced and aligned with each other. They are labeled top to bottom "Inputs, Controller, Outputs and Monitoring." There are arrows showing the flow of information through the TFCS. There is an arrow extending out of the top of the Field Sensors graphic into the Inputs cuboid. There is an arrow extending out of the bottom of the of the Inputs cuboid to the Controller cuboid. There is an arrow extending out of the Controller cuboid to the Outputs cuboid. There is an arrow extending out of the Outputs cuboid to the Monitoring cuboid. There is a double arrow extending from the left side of the Monitoring cuboid back up to the left side of the Controller cuboid. This line has a label associated with via a dotted line. The label says "Controller/Monitor Communications Used in NEMA TS 2 and ITS Cabinets." There is a line extending from the ride side of the Outputs cuboid to the top of the Field Displays graphic.)

Graphics: Ralph W. Boaz

Figure 7. Basic TFCS Operation.

 

Table 1. Differences in Transportation Field Cabinet Systems.

TFCS Physical Mounting Internal Bus Signal Monitor Input Channels Monitored Output Channels
NEMATS1 Shelf Parallel / Discrete Wiring Conflict Monitor 8 3/6/12/18
Caltrans Model 33X Rack Parallel / Discrete Wiring Conflict Monitor 44 16/18
NEMATS 2 Shelf Serial 153.6 kbps Malfunction Management Unit 64 16
ITS Cabinet v01 Rack Serial 614.4 kbps Cabinet Monitor Unit 120 28

Figure 8. ATC 5401 Standard allows applications to share the resources of the ATC Controller Unit and TFCS. Please see the Extended Text Description below.

(Extended Text Description: This graphic illustrates a TFCS being used in multiple applications areas. There is an aluminum looking cabinet in the center of the graphic. The cabinet has a door with a horizontal handle on the left side of the cabinet and two vent slots in the center top. The cabinet is about 2.5 times high as it is long. It is about 25% of the graphic height. To the left, to the right, lower left and lower right of the cabinet graphic are four rounded rectangles. There are double arrows between the cabinet and the rounded rectangles. The left and right rounded rectangles are about 30% of the height and 25% of the width of the graphic. The lower rounded rectangles are about 20% the height of the graphic and 25% of the width of the graphic. The rounded rectangle to the left has a label "Intersection Control" on the inside top. The remainder of the rounded rectangle is a graphic of a roadway intersection. The view of the intersection is such that two traffic signals are shown. The rounded rectangle to the right has a label "Ramp Metering" on the inside top. The remainder of the rounded rectangle is a graphic of freeway on-ramp. A freeway is depicted and a traffic signal with a sign "One Vehicle Per Green" is shown at the edge of the onramp. The rounded rectangle to the lower left has a label "Connected Vehicle V2I" on the inside top. The remainder of the rounded rectangle is a graphic of a 2-door sedan sitting next to a TFCS. The rounded rectangle to the lower right has a label "Other Application" centered within the rectangle with no other graphics included. In the upper part of the graphic is a square about 25% the height of the graphic representing a LCD screen and keypads portion of a transportation controller.)

Figure 8. ATC 5401 Standard allows applications to share the resources of the ATC Controller Unit and TFCS.

 

4. Glossary

TERM DEFINITION
Model 170 A traffic control device that meets one of the California Department of Transportation (Caltrans) standards for Model 170 traffic control devices.
Model 2070 A traffic control device that meets one of the California Department of Transportation (Caltrans) standards for Model 2070 traffic control devices or one of the standards for the ATC 2070 traffic control devices.
AASHTO American Association of State Highway and Transportation Officials
API Application Programming Interface. In this standard, when API is used by itself as a noun it refers to the software that is compliant to the ATC API Standard.
API Managers API software that manages an ATC resource for use by concurrently running application programs.
API Utilities API software not included in the API Managers that is used for configuration purposes.
Application Program Any program designed to perform a specific function directly for the user or, in some cases, for another application program. Examples of application programs include word processors, database programs, Web browsers and traffic control programs. Application programs use the services of a computer's O/S and other supporting programs such as an application programming interface.
ASCII American Standard Code for Information Interchange. A standard character-coding scheme used by most computers to display letters, digits and special characters. See ANSI-X3.4-1986(R 1997).
ATC Advanced Transportation Controller
ATC Device Drivers Low-level software not included in standard Linux distributions that is necessary for ATC-specific devices to operate in a Linux O/S environment.
Aux Switch A physical "auxiliary" switch on the Front Panel of ATC 2070 controllers that may be used by application programs.
BIU Bus Interface Unit. A transportation cabinet device which is used for communications within some cabinet systems.
Board Support Package Software usually provided by processor board manufacturers which provides a consistent software interface for the unique architecture of the board. In the case of the ATC, the Board Support Package also includes the O/S.
BSP See Board Support Package.
CMU Cabinet Monitor Unit. A transportation cabinet device which monitors the operational status of some cabinet systems.
CPU Central Processing Unit. A programmable logic device that performs the instruction, logic and mathematical processing in a computer.
Device Driver A software routine that links a peripheral device to the operating system. It acts like a translator between a device and the application programs that use it.
TERM DEFINITION
DRAM Dynamic Random Access Memory
DST Daylight Saving Time
EEPROM Electrically Erasable, Programmable, Read-Only Memory. EEPROMs differ from DRAMs in that the memory is saved even if electrical power is lost.
ELF Executable and Linking Format. A software library format.
Epoch An origin of time measurement commonly used in computers. It is midnight UTC of January 1, 1970.
FAT File Allocation Table. A Microsoft Windows file system format.
FHWA Federal Highway Administration
FIFO First In/First Out. A method of storage in which the data stored for the longest time will be retrieved first.
FIO Field Input and Output
FSA Failed State Action
FTP File Transfer Protocol. A protocol used to transfer files between computers on a network.
GMT Greenwich Mean Time
I/O Input/Output
IEC International Engineering Consortium
IEEE Institute of Electrical and Electronics Engineers
IPv4 Internet Protocol version 4. The fourth revision in the development of the Internet Protocol (IP). Addresses are usually written in dot-decimal notation, which consists of four octets of the address expressed in decimal and separated by periods.
ISO International Organization for Standardization
ITE Institute of Transportation Engineers
ITS Intelligent Transportation Systems
JC Joint Committee
kbps Kilobits per second (thousands of bits per second)
LED Light Emitting Diode. A display technology that uses a semiconductor diode that emits light when charged.
Linux Device Drivers Low-level software that is freely available in the Linux community for use with common hardware components operating in a standard fashion.
Linux Kernel The Unix-like operating system kernel that was begun by Linus Torvalds in 1991. The Linux Kernel provides general O/S functionality. This includes functions for things typical in any computer system such as file I/O, serial I/O, interprocess communication and process scheduling. It also includes Linux utility functions necessary to run programs such as shell scripts and console commands. It is generally available as open source (free to the public). The Linux Kernel referenced in this standard is defined in the ATC Controller Standard, Section 2.2.5, Annex A and Annex B.
Mb/s Mega/Million Bits per Second
TERM DEFINITION
MMU Malfunction Management Unit. A transportation cabinet device which monitors the operational status of some cabinet systems.
Ms Millisecond. One thousandth (10-3) of a second.
NEMA National Electrical Manufacturers Association
NEMA Controller A traffic control device that meets one of the NEMA standards for traffic control devices.
Operational User A technician or transportation engineer who uses the controller to perform its operational tasks.
O/S Operating System
PCB Printed Circuit Board
Process A process is an instance of a program running in a computer. In Linux, a process is started when a program is initiated (either by a user entering a shell command or by another program). A process is a running program in which a particular set of data and unique process identifier (ID) is associated so that the process can be managed by the operating system.
Programmatic Having to do with a computer program or software.
RAM Random Access Memory
RTC Real-Time Clock
SDD Software Design Document
SDLC Synchronous Data Link Control. A communication protocol used in some transportation cabinet systems.
SDO Standards Development Organization
SIU Serial Interface Unit. A transportation cabinet device which is used for communications within some cabinet systems.
SRAM Static Random Access Memory
SW Software
Telnet Teletype Network. A network protocol used on the Internet or local area networks to provide a bidirectional interactive communications facility.
TFCS Transportation Field Cabinet System
TOD Time of Day
TTL Transistor Transistor Logic
WG Working Group
USDOT United States Department of Transportation
USB Universal Serial Bus. An external peripheral interface standard for communication between a computer and external peripherals.
User Developer A software developer that designs and develops programs for controllers.
UTC Coordinated Universal Time. A high-precision atomic time standard. Time zones around the world are expressed as positive or negative offsets from UTC. As the zero-point reference, UTC is also referred to as Zulu time (Z). UTC is often referred to as Greenwich Mean Time (GMT) when describing time zones.

 

5. Reference to Other Standards

 

6. References

 

7. Study Questions

1) Which of the following elements of the TFCS is not shared by API Software?

  1. Outputs
  2. Inputs
  3. Controller
  4. Power

2) Which of the following statements is TRUE regarding the operation of the Front Panel Manager Window?

  1. The Default Window is always position [1] on the Front Panel Manager Window
  2. An Intersection Control window comes standard with the API Software
  3. Pressing {**,<ESC>} causes the Front Panel Manager Window to be put in focus
  4. The Front Panel Manager is designed for an 8 line display only

3) Which of the following is TRUE in regards to the Field I/O Management of API Software?

  1. All application programs may have read access to all of the input points
  2. All application programs may have write access to all of the input points
  3. All application programs may have write access to all of the output points
  4. Application programs must communicate with each other to avoid writing to the same output points

4) Which of the following is not a standard utility provided in API Software?

  1. Ethernet
  2. Bluetooth
  3. Linux/API Information
  4. System Time

5) Which of following parts of the ATC Engine Board is not managed by API Software?

  1. Front Panel Port
  2. Real-Time Clock
  3. General Purpose Serial I/O Ports
  4. Field I/O Ports

6) What must a User Developer do to make an application portable and compatible on two different ATC controllers in different TFCS architectures? Choose the best answer.

  1. Write the application software so that it uses the API Standard function calls whenever they are applicable
  2. Compile and link the application source code with API libraries
  3. Compile and link the application source code for the ATC Engine Board used in each controller
  4. All the above

7) What is NOT a benefit of the API Reference Implementation?

  1. Guarantees bug free software
  2. Lowers development cost to the industry
  3. Best opportunity for consistent API Software behavior
  4. Promotes collaboration of developers across the transportation industry