Attachment 2 - Traffic Report · MCU13/0251

APPENDIX B: PAGE 2 OF 5: JOINT EXPERT REPORT FROM PREVIOUS APPROVAL




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[OCR of page images]
HEH T CHE

HOLLAND TRAFFIC CONSULTING [2

APPENDIX B: PAGE 2 OF 5: JOINT EXPERT REPORT FROM PREVIOUS APPROVAL

Discussion of Traffic Engineering Issues in Dispute
1. Impacts of Generated Traffic

The traffic engineers are reliant on manual traffic counts undertaken in May 2007 at the site access
intersection and automatic traffic counts undertaken around the Heron Street roundabout in
January 2009. It was noted that the 2007 afternoon peak counts probably did not commence until
sometime after the actual afternoon peak period.

The traffic engineers have interpreted this basic data, and made projections of design traffic
generations of the subject development and of future traffic volumes.

The traffic report originally submitted in support of the application estimated future background
traffic growth as 5 percent per annum. It was agreed that such a growth rate is unreasonably high,
and that it would be more reasonable to assume background traffic growth of 3 percent per annum,
or 33 percent between 2009 and 2020, the appropriate traffic design horizon.

The basic data and the future traffic estimates made by the two engineers are set out in the
attached Table 1.

It will be noted that Mr Beard’s future traffic volume estimates through the subject intersection are
only marginally different from those prepared by Mr Holland. The estimates of design traffic
generations made by the two engineers are substantially similar, although there is slightly greater
difference between the estimates of turning traffic volumes without the subject development,
particularly in the afternoon peak period. :

Both engineers have assessed the future performance of the site access intersection with David
Low Way using the SIDRA Intersection analysis package.

Mr Holland assessed the future performance of the site access intersection with the subject
development as satisfactory, based on the use of design gap acceptance parameters of:

critical gap 5.0 seconds,

follow-up headway 3.0 seconds,
based on his interpretation of Table 13A.1 of Chapter 13 of the DMR Road Planning & Design
Manual, and the recommendations of the Austroads publications “Guide to Traffic Engineering
Practice”.

Mr Beard assessed the future performance of the site access intersection with the subject.
development as unsatisfactory, based on the default gap acceptance parameters used in the SIDRA
package for the nominated intersection geometry, a different interpretation of Table 13A.1
referenced by Mr Holland, and Table 4.3 from Austroads Guide to Traffic Engineering Practice
Part 5 — Intersections at Grade. He believes that the SIDRA default values (7.0 seconds and 4.0
seconds respectively) are generally appropriate, and considers that the minimum values which
could be reasonably assumed at the subject intersection are:

critical gap 6.0 seconds, and

follow-up headway 4.0 seconds.

The differences between the assessments made by Mr Holland and Mr Beard depend more on the
assumptions as to the gap acceptance parameters than they do on their traffic volume forecasts.

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