Basic HTML Version
154
Traffic Signal Systems Operations and Design: Isolated Intersections
System component
Delay, sec/veh (level of service)
Base case (C = 90 sec)
Option 1 (C = 60 sec; green times changed)
Approach
Northbound
Southbound
Eastbound
Westbound
7 (A)
13 (B)
12 (B)
13 (B)
11 (B)
19 (B)
19 (B)
17 (B)
Movement
NBLT
NBTH
NBRT
5 (A)
11 (B)
5 (A)
10 (A)
15 (B)
10 (A)
SBLT
SBTH
SBRT
4 (A)
20 (B)
4 (A)
8 (A)
30 (C)
4 (A)
EBLT
EBTH
EBRT
10 (A)
30 (C)
10 (A)
5 (A)
15 (B)
10 (A)
WBLT
WBTH
WBRT
25 (C)
35 (C)
5 (A)
19 (B)
20 (B)
5 (A)
Table 14.
Performance data
Visualization and Numeric Data
The final step in the description of the performance of a system, and in the comparison of a base case with a
proposed change, is what you would “see” in the field and how you would describe what you see. You could
use such descriptions as:
•
The standing queue on the eastbound through lanes clears before the end of green
•
The traffic on the southbound left turn lane backs up out of the left turn pocket, thus delaying all traffic
on the southbound approach
•
Much of the green time on the eastbound through lanes is not utilized indicating a possible misallocation
of time for this approach and the others
•
Vehicles on the westbound through lane must wait through two cycles
This gets us to the final step in the “learning to see” process, integrating the visual observations that you
make (and your description of them) with the numerical data that you collect in the field or from a simulation
model. You will learn in this chapter when you construct your simulation model to see both the “visual” and
the “numbers” and the conclusions that you can make from one reinforcing the other.
Learning to integrate the visual and the numbers also takes us to the experience of the traffic engineer, and
understanding the connection between the traffic controller and its effect on the user. What do you see in the
field and thus what should you change in the traffic controller? This is learning to be in the mode of the traffic
engineer standing in the field: one eye on the traffic flow and other on the controller. Making these connections
is what this chapter is all about.
A
ctivity
25: M
icrosimulation
M
odels
and
the
T
raffic
C
ontrol
S
ystem