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
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 is being implemented citywide. To date, ATSAC has been implemented at 3,100 of 4,300 City of Los Angeles signalized
intersections, with another 157 being designed and 133 under construction this year. We have received funding commitments for an additional 650
intersections, which will leave 243 locations or six percent of the system yet to be funded and constructed. Non-City grant
funding has provided approximately two thirds of all implementation costs.
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, located four floors below the street in the City Hall, 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 270
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
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.