System Architecture

The LA County IEN is a multi-tiered, hierarchical system with site, regional, and external interface components.

LA County IEN System Architecture

Site Components

IEN site components are installed at each participating agency. Site components include the following:

A Site Server to manage the distribution of data between local workstations, local traffic control systems, and the regional server
One or more Workstations to run the IEN User Interfaces
One or more Traffic Control Systems (TCS) with IEN command/data interface (CDI) software. CDI software connects an IEN Site Server and a Traffic Control System.
A network firewall to enforce secure connections between IEN and agency networks

See Connection Requirements for more information on the site components.

Regional Components

Regional IEN components are located at Los Angeles County DPW and provide the central servers for the IEN system. Regional components include the following:

A Regional Server to manage the distribution of data between sites. Additional Regional Servers can be added to increase the capacity of the system.
A Database Server to maintain system configuration information and historical status, event management, and alarm data.
Utility Servers that provide supporting services for the IEN systems such as Active Directory, DNS, and time synchronization.
Terminal Services Servers to provide access to the IEN Workstation software for remote users that connect to LA County's Virtual Private Network (VPN).

External Interfaces

TCS Command/Data Interface

The IEN has established a specification for CORBA-based command/data interface applications that connect traffic control systems into the IEN. A CDI allows the IEN to read a limited set of intersection, section, and detector data from a traffic control system, and enables the IEN to send a limited set of commands to intersections and sections on the TCS (as permitted by the owning agency). IEN CDI applications have been developed for the following types of traffic control systems:

McCain QuicNet
TransCore Series 2000
TransCore TransSuite TCS
Siemens i2TMS
Kimley-Horn KITS

LA County is developing an XML-based version of the CDI to better leverage national standards and to support traffic control system vendors that don't wish to develop CORBA interfaces to their systems.

LADOT-to-IEN Interface

The following customized interfaces have been developed to share data between LA County's IEN system and the Los Angeles Department of Transportation's (LADOT) Automated Traffic Surveillance and Control (ATSAC) system:

LADOT-to-IEN Interface: pulls LADOT intersection, system detector, and planned event data from LADOT's Web Server into the IEN.
IEN-to-LADOT Interface: pulls IEN intersection, system detector, and event data into LADOT's ATSAC system.

The LADOT-to-IEN Interface allows the IEN to display status data for all of LADOT's 3,400+ intersections and 11,000+ arterial system detectors. The interface collects intersection and arterial detector data from an LADOT Web Server, translates that data into IEN data, and passes the data to the IEN's internal data distribution subsystems. The LADOT Web Server reports a subset of the data that the IEN typically requests from other traffic control system vendors through their IEN CDIs. Specifically, data such as the intersection controller type, the master and local cycle counters, actual cycle length and offset for controllers running in non-adaptive mode, and vehicle call status are not available for LADOT intersections. In addition to traffic signal data, the LADOT-to-IEN interface also reports LADOT planned event information, which is not included in other standard deployments, since they are limited to traffic signal data. This planned event data can include scheduled road closure information for events such as demonstrations, parades, and sports games.

The IEN-to-LADOT Interface collects intersection and arterial detector data from the IEN using the IEN's internal CORBA-based interfaces. The interface is maintained by LADOT.

Freeway Data Interface

The IEN has developed a Freeway Data Interface application to pull data from the Regional Integration of Intelligent Transportation Systems (RIITS) and PeMS (Performance Measurement System) systems into the IEN. The Freeway Data Interface allows the IEN to report freeway congestion status, incidents, and lane closures to IEN users. The Interface was completed in September 2010.

IEN Web Server

The County has developed an XML-based web service to provide summary intersection and arterial detector data to authorized external systems. The IEN Web Server is currently not accessible from the Internet. Please contact Los Angeles County for more information. The Web Server was completed in September 2010.

Network Connections

Participating agencies must connect to central IEN servers that are located at the LA County Transportation Management Center (LACO TMC). LA County supports various types of network connections including dedicated network links (T-1, Frame Relay, Wireless, etc...) and site-to-site Virtual Private Network (VPN) connections over the Internet. Each agency's IEN site components communicate solely with the regional IEN components located at the LACO TMC. They do not communicate with site components at other agencies. The network link between an agency and the LACO TMC should have at least 384Kbps of bandwidth dedicated to IEN traffic. The IEN can be configured to support lower bandwidth connections if necessary.

Database Services

All static configuration data for the IEN is maintained in a relational database on the Database Server. This configuration data consists of the following:

Security attributes for users and resources
The set of TCS devices known to the system
Alarm notification and coordination monitoring configuration
Locations and attributes of network resources
Scenario response plans

In addition to the static configuration data, the IEN database stores traffic event data, archived arterial and freeway congestion status data, alarm data, intersection coordination history, and system event logs.

Access to IEN User Interfaces From the Internet

LA County allows authorized users to access the IEN User Interfaces over the Internet through the County's VPN. The VPN connection can be established using an Internet Browser from any system that has access to the Internet. The IEN User Interfaces are hosted on a Terminal Services Server located at the LACO TMC. The first Terminal Services Server was deployed in Spring 2010. Please contact LA County for further information.