Sunshine Butterflies - Attachments A - C - 010816

Rural Basic Right Turn Treatment (BAR) and Basic Left Turn Treatment (BAL) – Refer Drawing
No. 16520_SK_1

The BAR is the minimum treatment required to enable right turn movements from a through road to
an access point. The layout includes sufficient width for through vehicles to pass on the left side of a
stationary right turning vehicle, through widening of the road shoulder.

As there are good overtaking opportunities within this section of McKinnon Drive Tod Consulting
would recommend the installation of barrier centre line, to discourage passing manoeuvres.

As the majority of traffic will be coming from and returning top Tewantin there will be very few left
turns into the site. We therefore do not consider a BAL necessary.

Sight Line Requirements for Access

It is essential for safety reasons that drivers approaching from all directions can recognise the
presence of a driveway in time to slow down or stop to avoid potential collisions, with turning traffic. It
is therefore necessary to have adequate sight distances in relation to both horizontal and vertical
geometry.

Tod Consulting have undertaken an assessment of the sight line requirements for the proposed
access, in accordance with the Austroads Guide to Road Design – Parts 3, 4 and 4A.

This guideline states that sight distances at accesses should comply with the sight distance
requirements for intersections i.e. that Approach Sight Distance (ASD), Safe Intersection Sight
Distance (SISD) and Minimum Gap Sight Distance (MGSD) are achieved.

In accordance with these guidelines the calculation of all necessary sight lines has assumed a driver
reaction time of 2.5 seconds for rural areas. McKinnon Drive has a speed limit of 100km/hr, and as
such in accordance with the Austroads guidelines a design speed of 110km/hr has been used in
calculating the required sight distances.

When calculating sight distances we have included grade correction factors, in accordance with the
Austroads guidelines, where necessary to account for the additional distance that vehicles travel
when braking on a downhill grade and vice versa.

1.      Approach Sight Distance (ASD)

ASD is required on the main road approaches so that drivers can see the pavement and road
markings at the proposed access. ASD is measured from driver’s eye height (1.1m) to 0.0m.

                                Approaching from Cooroibah               Approaching from Tewantin
                                      (1.5% up grade)                         (1% down grade)
                                Austroads                               Austroads
                                                  Achieved                                Achieved
                               Requirements                            Requirements
  Approach Sight Distance
                                  202m *          Approx. 320m         216m *          Approx. 320m
           (ASD)
* Note: The required sight distances vary for each of the approaches due to grade correction factors.




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Tod Consulting Project No. 16520