|
Class 21 - 5 April 2007
Objectives for today:
- Understand traffic controller
subsystem
Topics:
- Review results from Exam 2
- Precedence diagrams
- Scheduling concepts
- More background on VB and
controller logic
Research paper
Due today:
Task 1. Submit a bibliography or reference list, using correct citation
format (see pp 9-10 of
Transportation
Research Board format), on relevant papers and reports by April 5th
(Class 21).
Class notes:
Written notes
Questions on today's class:
1. Figure 1 from the article "Modeling
Traffic Signal Operations using Precedence Graphs" shows a precedence
graph representation for a single phase. The legend below the picture
shows the various interval and the elements of the graph. So we have
here Fixed Duration Interval (solid arrow) and Variable Duration
Interval (zigzag arrow). There is also precedence graph for the
T-intersection on Figure 3. Here we have overlap D and one of its parent
phase is phase 1. The article further says that overlap inherits all
clearance interval times form the parent phase. I wonder why for the
overlap D the duration of Yellow and Red are presented as Variable
Duration Interval (zigzag arrow)? Shouldn't it be the same as for the
parent phase 1-Fixed Duration Interval?
Response: I think that this is a mistake as the yellow and red
intervals should be fixed duration. Thanks for catching this! 2. Three types
of overlaps are mentioned. They are as follows: minusGreenYellow (which
is used when the distance form two T-intersections is short, for
example). There is also normal type of overlap. And the table 3 says the
third type is "other"? What would be the other types of overlap?
Response: I don't know the response to this question and will try to
find out.
3. The same table has modifier phases.
I do not understand this term modifier phase? Could you please explain
to me this term? .
Response: I don't know the response to this question and will try to
find out.
|
