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What is the ATSAC System?
The Automated Traffic Surveillance and Control (ATSAC) System is the centralized traffic control center for the City of Los Angeles.  The system provides real-time monitoring and adjustment of signal timing for nearly 4,600 signalized intersections citywide.  The system has been shown to reduce travel time by 12% and increase speeds by 16%.

Where does the information on the TrafficInfo Site come from?
Citywide there are over 20,000 loop detectors located at signalized intersections.  These detectors collect information on vehicles as they pass over them and this information is sent to our centralized traffic control center.  From this information we can estimate travel speeds on city streets.  This is the only source for traffic information you see on our website and is not provided by any third party. 

Why is there no data from freeways or adjacent cities?
The ATSAC System only manages traffic signals within the City of Los Angeles.  Freeways are managed by Caltrans and adjacent cities have their own traffic control systems. See the Caltrans QuickMap here: http://quickmap.dot.ca.gov/

How to use the Map
To find your area, try clicking on the neighborhoods on the righthand side of the page.  Otherwise, try using the pan and zoom control in the upper righthand corner of the map.  The color coded lines indicate how fast vehicles are moving along that street.

Background
According to many opinion polls, traffic congestion and associated delay is a major public concern. As population increases, intensification of land use occurs which results in even greater congestion. With increased congestion comes air quality problems and added fuel consumption. Improving the efficiency of the existing highway system through the implementation of advanced technologies, with the coordinated efforts of various public agencies and the private sector, is one of the best ways to alleviate traffic congestion.

One such method of optimizing the existing highway system is through implementation of the Automated Traffic Surveillance and Control (ATSAC) System. Based on the successful performance of the Coliseum Area ATSAC System during the 1984 Olympic Games, the ATSAC System has been implemented citywide. To date, ATSAC has been implemented at over 4,600  signalized intersections.

ATSAC is a computer-based traffic signal control system that monitors traffic conditions and system performance, selects appropriate signal timing (control) strategies, and performs equipment diagnostics and alert functions. Sensors in the street detect the passage of vehicles, vehicle speed, and the level of congestion. This information is received on a second-by-second (real-time) basis and is analyzed on a minute-by-minute basis at the ATSAC Operations Center,  to determine if better traffic flow can be achieved by changing the signal timing. If required, the signal timing is either automatically changed by the ATSAC computers or manually changed by the operator using communication lines that connect the ATSAC Center with each traffic signal. To supplement the information from electronic detectors, closed-circuit television (CCTV) surveillance equipment has been and continues to be installed at critical locations throughout the City. The Department has installed CCTV cameras at nearly 500 locations and new sites are being added. The major benefit of the ATSAC System is the ability to effectively manage dynamic traffic flow. Evaluation studies of the ATSAC System show that travel times, traffic signal delay, vehicular stops, air emissions and fuel use are significantly reduced.

Another benefit derived from the installation and operation of the ATSAC System is the ability to dynamically add new traffic control features through software as they become necessary without building new systems or replacing large quantities of hardware. An example of this is the ability to provide special control schemes for the management of transit vehicles on major commuter corridors within the City. Enhanced operation of surface street operation of the Metro Blue Line (light rail transit) is made possible through modification to the ATSAC software both at central control and at the local intersections. Through options allowed by the modified software, system operators can provide appropriate control for both light rail trains and on-street vehicles. Additional features also available through software additions to the system will allow for bus priority operation along major bus commuter routes. ATSAC also provides the capability to continually measure traffic volumes and congestion levels for analysis of trends and other transportation planning purposes. The Adaptive Traffic Control System (ATCS) is the latest enhancement to ATSAC and uses a personal computer-based traffic signal control software program which provides fully traffic adaptive signal control based on real-time traffic conditions. The ATCS will automatically adjust traffic signal timing in response to current traffic demands by allowing ATCS to simultaneously control all three critical components of traffic signal timing, namely cycle length, phase split and offset.

In 1992, the City's ATSAC system received the distinguished award "Innovations in State and Local Governments" from the Ford Foundation. In 1993, the City was one of only 16 cities to receive federal transportation funds to demonstrate the feasibility of promising new high technology and conversion of defense technology. The federally funded Spread Spectrum operational test, in partnership with Hughes Aircraft, shows promising results in reducing project cost and construction time for computerized signal systems. In 1994, the Department received the ITE Transportation Achievement Award for our work in quickly restoring mobility in the wake of the Northridge Earthquake. The presence of ATSAC along the Santa Monica Freeway Corridor was cited as a key component in maintaining circulation despite the loss of the nation's busiest freeway. In 1995, the Santa Monica Freeway Smart Corridor Demonstration Project was selected to receive the "Best in Category" award (Transportation Technology category) under the U.S. Department of Energy's 1995 National Awards Program for Energy Efficiency and Renewable Energy.

 
 
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