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Problem 4 - Page 2 of 2 |
ID# C104002 |
Problem 4:
Actuated Control
The traffic-actuated
timing procedure requires three control parameters:
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Minimum
phase times, considering driver expectancy and pedestrian requirements. The minimum times from the pretimed example (sub-problem
1b) will be used here. |
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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 multiple-lane 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/Styner-Lauder Avenue intersection:
Sub-problem 4a: Estimating phase times
for actuated signal control
Sub-problem 4b: Effects of Unit
Extension on intersection operating characteristics
Sub-problem 4c: Coordinating a system of
actuated controllers
Sub-problem 4d: Coordinated operation of
an actuated controller with left-turn protection
[ Back ] [ Continue ] to Sub-Problem 4a |
