Traffic response · MCU18/0019

Information required
5. Investigate and provide amended plans locating the access further south along Val Crescent.
Response
The proposed driveway on Val Crescent has been positioned to:
    • maximise sight distance in both directions i.e. to the right, towards traffic approaching from the
        Goodchap Street roundabout, and to the left, towards traffic approaching around the horizontal
        bend on Val Crescent;
    • minimise impact upon residential amenity i.e. minimise the number of dwellings that traffic
        associated with the development (both light and heavy vehicles) will need to travel past to access /
        egress the development; and
    • avoid the tree protection zone surrounding the existing gum tree to the west of the proposed access
        driveway location.
In light of the above, it is not considered feasible or desirable to reposition the driveway.
6. Should the proposed Val Crescent access location be utilised, demonstrate the achieved sight lines are
in accordance with Austroads Safe Intersection Sight Distance (SISD) requirements on a scale plan in
both directions along Val Crescent from the driveway, and justify those sight lines. The plan should
include any proposed fencing, landscaping, and retaining walls in that vicinity.
Response
The Safe Intersection Sight Distance (SISD) recommendations in Austroads Guide to Road Design are
typically applied at intersections, as opposed to site access driveways. Furthermore, Austroads is a
guideline document only. The statutory requirement for sight distance in this instance is that stipulated in
Australian Standard AS2890.1.
As outlined in the Traffic Report which accompanied the development application, a sightline assessment
was undertaken in light of the proximity of the proposed driveway to adjacent road features.
In order to achieve adequate sight distance from the exit side of the driveway towards traffic turning left
from Goodchap Street into Val Crescent (noting that these traffic volumes are expected to be low), it was
recommended that the area as identified in Figure 1 over page be kept clear of any obstructions, including
fences or landscaping. This would provide approximately 40m – 45m of stopping sight distance (SSD)
which achieves the desirable minimum assuming a (conservatively high) vehicle approach speed of
40km/hr and a reaction time of 2 seconds, based upon the provisions of Austroads Guide to Road Design
Part 3 – Geometric Design (Table 5.4). This would also exceed the minimum SSD stipulated in Figure 3.2
of AS2890.1, assuming a (conservatively high) frontage road speed of 40km/hr, which is 35m.
Furthermore, this would provide a 5 second gap for heavy vehicles to exit the site (which is the minimum
recommended in AS2890.2) assuming an average approach traffic speed of 30km/hr, which is considered to
be a more realistic travel speed for traffic turning left from Goodchap Street into Val Crescent.
Sight distance from the exit side of the driveway towards traffic approaching from the west (i.e. the bend in
Val Crescent) would also exceed the 35m – 40m minimum required under the provisions of Austroads
Guide to Road Design and AS2890.1, and the 42m required under the provisions of AS2890.2, assuming
that vehicles take this bend at 30km/hr or slower. Given the radius of this bend, it is considered unlikely
that traffic would travel around this corner at greater than 30km/hr.
The observation angle in both directions is approximately 110 degrees, which achieves the recommendation
in Section 3.2.3 of Austroads Guide to Road Design Part 4a: Unsignalised and Signalised Intersections
(notwithstanding the fact that the access is a driveway, not an intersection).
In light of the above, subject to the area identified in Figure 1 over page being kept clear of any
obstructions including fences or landscaping, the proposed access driveway location is considered to be
acceptable from a traffic engineering perspective, taking into consideration the existing site conditions and
other design requirements.

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Our Ref: 290_KNG01                                                                                 2 May 2018