ATTCH 6 - IR Response - Traffic (TTM)

the normal design domain (NDD) criteria. The impracticality of satisfying NDD criteria is due to the
constraints imposed by both the vertical and horizontal geometry of David Low Way.

The SISD requirements (based on EDD) for the proposed site access have been assessed based on an 80kph
design speed (ie posted 70kph speed limit plus 10kph) for the ‘normal day’ car scenario, whilst the other
mandatory design case, the ‘truck day’ scenario, has been assessed based on a design speed of 70kph (ie
80kph car design speed minus 10kph).

To validate these design speeds, a survey of existing vehicle speeds was carried out by TTM between
Thursday October 26, to Wednesday November 1, 2017. The results are summarized below (and included as
an attachment):

Northbound traffic

          85th percentile speed for light vehicles = 68.22kph
          85th percentile speed for heavy vehicles = 67.59kph

Southbound traffic

          85th percentile speed for light vehicles = 73.44kph
          85th percentile speed for heavy vehicles = 73.80kph

These surveyed 85th percentile speeds are generally slower than those used for determination of the
required SISD.

Based on the 70/80kph design speeds, the resultant SISD requirements are 110m (normal day car scenario)
and 134m (truck day scenario).

Long section drawings prepared by Sheehy and Partners, indicate that these sight distances can be achieved.

TTM believe that an SISD can be achieved at the proposed site access which complies with the Austroads
EDD criteria, noting that there may be a requirement for vegetation clearance and/or benching of the local
landform.



14.       Modify the proposed site access design so that a HRV can turn into the site from wholly within the
          proposed BAL left turn lane, without using the adjacent through lane, so that the vehicle can wait in that
          lane clear of through traffic, if there is another vehicle waiting to depart from the access at that same
          time. Otherwise the site access should be redesigned to accommodate turning to the access by a HRV at
          the same time as a car is departing the site. Also, the taper for the proposed BAL treatment needs to be
          lengthened to comply with Austroads standards.