Adaptive Control Software – Lite (ACS-Lite) Implementation Template

saturated conditions once they have happened. In the near future, the ACS-Lite system
will be enhanced to adapt (increase) the cycle time to better handle saturated conditions.
4) Does the size of the loops used for vehicle detection affect the operation of
ACS-Lite?
The length of the loop is not critical to the performance of the algorithms. Standard loop
designs (e.g. 6’ advance loops/zones, 20-40’ stop bar loops/zones) have performed
adequately for all field tests. Better performance will be achieved with detection zones
that are separated out by lane-by-lane, but it is not necessary that the zones are separated
by lane.
5) Are the phase tuning detectors also used for local actuated operations?
Yes. The same detectors that are used to operate the intersection are used for collection
of the data for phase tuning.
6) Are the algorithms and software developed with FHWA funding readily
available? If so where?
The software will be available to agencies through each of the controller manufacturer
companies (Siemens, Econolite, Peek, and McCain).
7) Is there a logic identifying detector errors and a plan B under such
conditions?
The identification of detector errors/diagnostics is a function of the controller. Upon
receipt of a detector error message (e.g. max presence, erratic, or no activity) from the
controller, ACS-Lite will remove/neglect that detector from its calculations. When the
detector is repaired and starts reporting correct data again, the information is
automatically re-introduced into the calculations.
8) Does the ACS-Lite System archive signal timing for later use.
ACS-Lite stores all second-by-second phase timing data, detector data, and its control
decisions for later analysis for up to one month.
9) Is it possible in the future to have more than 12 intersections without the IP
communications?
ACS-Lite is capable of supporting more than 12 controllers on a serial communications
channel that is faster than 9600bps.
10) How does ACS-Lite handle incidents?
ACS-Lite handles incidents by modifying the splits and offsets of the traffic pattern (and
in the future - cycle time) to adapt to the increases and decreases in traffic flows on the
facility it is managing. Detector diagnostics/failure conditions are the responsibility of
the controller software (e.g. a stalled vehicle in a left-turn bay). ACS-Lite currently has