Traffic signal synchronization is a method
of timing groups of traffic signals along an arterial to provide
for the smooth movement of traffic with minimal stops. The quality
of the resulting progression is a function of the spacing of
the signals, the prevailing speed, the amount of traffic coming
in and out of driveways between traffic signals, the uniformity
of intersection sizes, and the cycle length. The traffic volume
and the proportion of the green time given to the preferred
movements are also important.
Synchronization Goals
Many drivers ask why they have to wait so
long for a signal to change. Many of these drivers are waiting
to enter a major arterial street from a side street. This is
even more frustrating when no traffic can be seen on the arterial.
To allow the coordination of the arterial, the side street must
wait until the main traffic movement on the arterial has gone
through the intersection. It is possible that the arterial traffic
can't be seen immediately, but will soon be passing through
the intersection.
The goal of synchronization is to get the
greatest number of vehicles through the system with the fewest
stops in a comfortable manner. It would be ideal if every vehicle
entering the system could proceed through the system without
stopping. This is not possible even in a well-spaced, well-designed
system. Therefore, in traffic synchronization, "the majority
rules" and the busiest traffic movements are given priority.
Depending on a route, the master cycle length of an arterial
could vary from 60 to 120 seconds. This means that if you were
exiting a side street, and you just missed the light, it is
possible to wait between 60 and 120 seconds, or whatever is
the cycle length, before receiving another green light. Generally,
the busier and the bigger the intersection, the longer the required
cycle length.
Not all City streets warrant synchronization.
Typically, a street is selected for synchronization if it carries
a certain amount of traffic along the arterial during peak hours.
Most of the City's major streets are selected, like Soledad
Canyon Road, Valencia Boulevard, Lyons Avenue, portions of McBean
Parkway, Orchard Village Road, portions of Bouquet Canyon Road,
and Seco Canyon Road. In most cases, synchronization is active
from 6:00 a.m. to 7:00 a.m. during weekdays. The individual
signals operate on a "first-come-first-served" or traffic activated
basis outside of these hours.
Synchronization Projects: Current and Future
The City has invested millions of dollars
for the installation of traffic signal interconnect in the past
years, using grant monies and developers' contributions. These
infrastructures have a two-fold function. First, they enable
a series of adjacent signals to time or function as a group
and not independently from each other. Second, they serve as
the communication link between traffic signals and City Hall.
This link enables City staff to observe and control the operation
of traffic signals from City Hall offices. This is a very effective
tool in better handling freeway detours and other incidents.
It enables City staff to adjust signal timing instantly in response
to emergencies. The City is now in the process of installing
a Traffic Signal Operations Center in City Hall where most of
the City's signals will be monitored and controlled. The synchronization
of traffic signals will be an ongoing effort by City staff.
It will be updated on a periodic basis to better handle the
changing traffic patterns.
If you have any questions regarding traffic
safety issues, please call the Traffic Engineering Division
at (661) 255-4942.
