Attachment 2 - Traffic Report · MCU13/0251

5.4 Intersection capacity analysis

Capacity analysis of the existing intersection has been undertaken using the widely accepted Sidra
package, using default settings, with a single lane approach on the unnamed road leg, and a short right
turn lane in David Low Way.

As indicated by Colin Beard in the JER, operation of the existing intersection, with the current approval
under year 2020 PM peak hour conditions with the current approval, using default Sidra gap acceptance
parameters, indicates unsatisfactory operation. The summary output from that analysis is attached at
Appendix D. This issue was overcome in the JER by adopting slightly lower gap acceptance parameters
than the Sidra defaults.

Obviously, if further traffic is generated by the proposed development, then the operating conditions
would be worsened compared with those associated with the existing approval. The standard Sidra gap
acceptance parameters could not be reasonably lowered to accommodate the additional traffic
generated by the latest proposal in a satisfactory manner.

There is an option to increase capacity of the existing intersection configuration by increasing the width
of the existing median in David Low Way at the intersection to 7.0m, and thus satisfy the requirements of
the Austroads Guidelines for a staged right turn arrangement, where the critical right turn movement from
the unnamed road firstly crosses the northbound David Low Way traffic stream, and then waits within the
wide median area before entering the southbound traffic stream. The 7.0m width requirement for such
an arrangement is documented in the Austroads Guide to Road Design – Part 4A, where Section 7.8.2
refers to Figure 4.13 as a form of 2 stage crossing, and Figure 4.13 states that medians of 7m or greater
are sufficient to shelter a car.

A sketch shown how this could be achieved follows:




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