Problem 4  Page 2 of 2 
ID# C104002 
Problem 4:
Actuated Control
The trafficactuated
timing procedure requires three control parameters:

Minimum
phase times, considering driver expectancy and pedestrian requirements. The minimum times from the pretimed example (subproblem
1b) will be used here. 

Maximum
phase times to assure a reasonable distribution of green time on cycles with
heavy demand. The literature contains a variety of techniques for setting
maximum green times. For purposes of this example, the maximum green
times will be set to their corresponding pretimed values. 
 Unit
extension times to determine the length of the gap in arriving traffic at
which a phase will terminate. Most traffic models, including the HCM, will
yield lower delay estimates with lower unit extension times. As a
practical constraint, however, the unit extension must be slightly longer
than the maximum expected gap between vehicles departing from a queue, or
premature phase terminations will occur. For the purposes of this example, the
unit extension times will be set to 3 seconds for single lane operation and
2 seconds for multiplelane operation. 
This
problem illustrates some of the important elements of performing an analysis
of a signalized intersection operating under actuated control by addressing
the following issues as they relate to the proposed signal at the U.S. 95/StynerLauder Avenue intersection:
Subproblem 4a: Estimating phase times
for actuated signal control
Subproblem 4b: Effects of Unit
Extension on intersection operating characteristics
Subproblem 4c: Coordinating a system of
actuated controllers
Subproblem 4d: Coordinated operation of
an actuated controller with leftturn protection
[ Back ] [ Continue ] to SubProblem 4a 