City of Greater Sudbury Transportation Study Report

4.6. Model Validation
Validation of the model involves comparisons of model simulations for a base year with
observed data collected in that base year. In the case of the Greater Sudbury model, the
observed data consists of the household survey data discussed in Section 3.1, which is
summarized in a trip table, and count data collected from Greater Sudbury and the MTO,
which is summarized, on a screenline basis.
The p.m. peak hour survey data is compared to the p.m. peak hour simulated trips on an
aggregated trip table basis with the aggregation being on the former Municipalities. A
comparison of the observed and simulated
trips is shown in Figures 4.6.1 and 4.6.2.
Figure 4.6.1 shows a direct comparison
between observed and simulated trips while
Figure 4.6.2 shows a comparison of the
natural log (LN) of the observed trips with the
LN of the simulated trips. The R-square
indicates that the model is producing
reasonable estimates of travel between the
former municipalities.
Comparisons of simulated p.m. peak hour
volumes with traffic counts at the screenline
level are shown in Table 4.6.1. Also shown is
Observed
Figure 4.6.1 Observed vs. Simulated P.M. Peak Hour Autos
14000
12000
10000
8000
6000
4000
2000
0
0 5000 10000 15000
Simulated
y = 0.9999x + 10.684
R 2 = 0.9961
Observed
Linear (Observed)
the screenline summary of the home interview survey data. The “inbound” represents trips
traveling towards the center of the City while the “outbound” represents trips traveling away
from the center of the City. The household survey was geo-coded to the traffic zone level
then assigned to the base year road network then summarized by screenline. In some cases
the count data was lower than the model simulation and the results of the household survey.
The p.m. peak hour count data was acquired from Greater Sudbury and from the MTO.
Some of these counts were in the form of intersection counts collected manually while others
were collected by Automatic Traffic Recorders (ATR) as part of the AADT count program.
Counts were not always available for recent
years, which meant that prior counts had to
be used. Also, in a few instances the p.m.
peak hour counts had to be estimated from
the AADT counts. Also, some of the
screenlines cross minor roads for which
counts were not available. Ideally, for model
validation purposes, the count data should be
collected using the same method and the
counts should all be done at the same time.
The lack of consistency in terms of timing and
the fact that some of the counts had to be
estimated makes it difficult to use for model
validation purposes. In spite of this,
Figure 4.6.2 LN(Observed) vs LN(Simulated) P.M. Peak
Hour Autos
0
0
-2
2 4 6 8 10
y = 1.0198x - 0.2318
R 2 = 0.8962
comparisons at the screenline level between the model simulation, the observed data from
the household survey, and the count data indicates that the model has been well calibrated
and validated. Figure 4.6.3 illustrates the screenlines used for the model validation.
LN(Observed)
10
8
6
4
2
Ln(Simulated)
LN(Observed)
Linear (LN(Observed))
CITY OF GREATER SUDBURY
OFFICIAL PLAN BACKGROUND REPORT
September 2005 Page 49