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USE OF TRIP TABLE ESTIMATION
TO IMPROVE PROJECT TRAFFIC
FORECASTS
13th TRB Planning Applications Conference
Reno, Nevada
The Corradino Group, Inc.May 12, 2011
13th TRB Planning Applications ConferenceReno, Nevada 1
Background
Estimate Future Project Traffic. I-95 in Southeast Florida. 64 mile Corridor Feasibility Study with
managed lanes. Model results must be:
Carefully reviewed.Adjusted.
Search for a Systematic Process.
The Corradino Group, Inc.May 12, 2011
13th TRB Planning Applications ConferenceReno, Nevada 2
Study Area Miami-Dade, Broward,
Palm Beach Counties Southeast Regional
Planning Model 3 time periods 4,284 TAZs Subarea with 2,123 TAZs
The Corradino Group, Inc.May 12, 2011
13th TRB Planning Applications ConferenceReno, Nevada 3
Subarea
Goals
Produce traffic estimates for morning and afternoon peaks.
Multiple target years: 2010, 2035, 2050. Make systematic adjustments. Minimize “post-processing”.
The Corradino Group, Inc.May 12, 2011
13th TRB Planning Applications ConferenceReno, Nevada 4
Method
Trip table estimation (Cube Analyst). Corrects for systematic errors. Productions and attractions not altered. Future volumes based on:
Adjusted Base
+ Growth (unadjusted future-base) Difference judged to be more reliable
than factors.
The Corradino Group, Inc.May 12, 2011
13th TRB Planning Applications ConferenceReno, Nevada 5
Requirements
4,284 TAZs seemed too big for Analyst. Subarea of 2,123 TAZs worked. Analyst worked better as an iterative
process (20), on a sample of traffic counts. Freeway counts chosen for every iteration. Arterial counts chosen randomly (about
10% used, each time).
The Corradino Group, Inc.May 12, 2011
13th TRB Planning Applications ConferenceReno, Nevada 6
Effectiveness
The Corradino Group, Inc.May 12, 2011
13th TRB Planning Applications ConferenceReno, Nevada 7
0 2 4 6 8 10 12 14 16 18 200.0%
5.0%
10.0%
15.0%
20.0%
25.0%
30.0%
35.0%
40.0%
45.0%
50.0%
Analyst %RMSE
AM
Off-PK
PM
Iteration
% R
MS
E
Changes in the Trip Table
The Corradino Group, Inc.May 12, 2011
13th TRB Planning Applications ConferenceReno, Nevada 8
AM PEAK
PM PEAK
OFF PEAK
0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00
7.11
6.96
7.65
6.60
6.31
7.30
Analyst Effect on Trip Distance
After
Before
Average Trip Distance (miles)
Tim
e P
eri
od
Conclusions/Caveats
Weigh against ad hoc or NCHRP 255-style adjustments.
Changes the average trip length, so some concern about the overall impact on traffic patterns.
Dramatic reduction in link-by-link assignment error.
Careful review of results still required. Post-processing adjustments still needed.
The Corradino Group, Inc.May 12, 2011
13th TRB Planning Applications ConferenceReno, Nevada 9
Acknowledgements
Florida Department of Transportation, District 4Shi-Chiang Li, AICPDerek Miura
The Corradino Group, Inc.May 12, 2011 13th TRB Planning Applications Conference: Reno, Nevada 10
