2016-02-02 I&S Committee - Item 4 - Attachment 1 - Noosa Traffic Study

achieved with implementation of a single lane roundabout at that intersection, although with a
second short lane on the southern Ernest St approach for through/right turn movements. To fit
an appropriate roundabout at that location would most likely require removal of that part of the
existing building on the south-west corner of the intersection that appears to encroach into the
road reserve, as well as resumption of a truncation on the north-eastern side of the intersection.
Ideally, a dedicated right turn lane would also be provided on the eastbound Hilton Tce
approach, but it is doubtful that this could be achieved without further property resumption (the
analysis results outlined below do not include this additional intersection feature).

With those improvements, under predicted 2036 conditions, the intersection is predicted to
operate with a degrees of saturation of 0.80 and 0.67 in the 2036 AM and PM normal peaks,
and 0.84 and 0.71 in the AM and PM holiday peaks.



5.2.4 Year 2036 – Memorial Ave / Doonella St intersection

The Memorial Ave / Doonella St intersection is already approaching its 0.85 DOS limit during
the AM peak and will need upgrading in the short term future.

The issue arises at the intersection during the AM Peak when there is a very heavy right turn
movement from Doonella St (west) into Memorial Ave (south) that must give way to traffic
travelling north through the roundabout on Memorial Ave, and also from Memorial Ave (south)
into Lake St (east). These opposing movements are relatively low, but due to their random
nature, are sufficient to cause a capacity issue with the heavy right turn movement from west to
south.

Upgrading to achieve sufficient capacity to the year 2036 would involve provision of separate
approach lanes on the southern Memorial Drive leg, with the left turn lane separated from the
through/right lane using a raised median, so that the through/right lane can be separately
metered, while leaving the high left turn volume from Memorial Ave (south) into Doonella St
(west) to continue to occur as a free flowing “give way” controlled movement as it does at
present.

The proposal is to meter the movements that oppose the heavy right turn from west to south,
so that those movements move through the intersection in a “block” rather than randomly, and
thus only interrupt the heavy right turn movement for short, defined periods of time, thus
significantly increasing the capacity of the heavy right turn movement.

Although Sidra analysis does not indicate any improvement in operating conditions at the
roundabout as a result of implementing the additional roundabout approach lane without
metering, it is possible that there would be some improvement in operating conditions with only
the additional lane. Hence, the works could be staged, with the additional lane implemented on
the southern Memorial Avenue leg first, potentially providing some operating improvement.
The roundabout metering to that leg of the intersection could be implemented as a second
stage as operating conditions worsen.

Importantly, the need for roundabout metering would only be only activated at the critical times
of each day, which in this case would be during the weekday morning peak hour only. At all
other times of the day and on weekends, the roundabout would operate without metering.

With those improvements, the intersection is predicted to operate with a degrees of saturation

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