What We Do


SATURN is a “meso” or middle tier traffic model.  It stands for Simulation and Assignment of Traffic on Urban Road Networks and it allows the user to undertake a variety of area wide strategic through to more detailed local area assessments. 

SATURN is a “congested assignment” model, which means that it properly reflects congestion at intersections (or indeed midblocks) and it holds traffic at those congestion points, with the assessment of conditions based on arrival rather than demand flows.  It is possible to undertake multiple user class assessments, with bus services (and bus priorities) and other vehicle types (such as high occupancy vehicles or trucks) able to be modelled separately. 

Flow has used SATURN for many years and for a wide range of applications, including:

  • Development of the New Zealand Transport Agency’s model of Auckland’s Upper Harbour area, to assess the (then) proposed SH18 Hobsonville Extension, which was opened to traffic in 2011
  • Expansion of the above model for use in the 2010 Additional Waitemata Harbour Crossing study, which considered bridge and tunnel options across the Auckland Harbour 
  • Development of a SATURN traffic model of the western half of the Auckland city centre, to assess the effects of the proposed development of the Wynyard Quarter on Auckland’s waterfront, for Auckland City Council
  • Extension of the above traffic model to cover the entire Auckland City Centre, in order to assess a number of short term issues, such as the proposed traffic management during the Rugby World Cup in 2011, and longer term measures such as the various proposals set out in Auckland Council’s City Centre Masterplan.


Auckland City Centre SATURN Model