Nationwide Speed Management Framework Rollout

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As part of the Safer Journeys 2013 – 2015 Action Plan, NZ Transport Agency was responsible for the nationwide rollout of the Speed Management Framework included in the Speed Management Guide.  This rollout was needed to assist local authorities to target the highest benefit opportunities on their network through speed management interventions.  A crucial part of efficiently rolling out the framework was to automate the Infrastructure Risk Rating (IRR) methodology, one of the three metrics needed to apply the framework.


Abley developed a GIS workflow to automate the calculation of IRR.  This involved the development of GIS models that accurately extract road attributes from various transport datasets and applying some assumptions based on engineering and professional judgement.  The automated process was initially tested on the Top of the South road network and then on the Waikato region.  The key part of the process was to utilise spatial data to segment roads according to various IRR attributes including land use, alignment, road width, road stereotype, intersection density and traffic volume and then assign risk based on these factors.  The outputs were delivered through the integration of IRR with other risk maps through a single mapping website.


The IRR methodology was successfully automated to assess road safety risk on all roads in the country.  The automated process was found to be very cost effective compared to manually undertaking the IRR methodology and enabled the efficient rollout of the Speed Management Framework nationwide.  The convenience of GIS allowed the process to be easily adjusted as it was being refined.  This application is of particular interest to any road controlling authority wanting to efficiently identify parts of their network where speed management intervention may be an appropriate response to improving road safety performance.

Business Area: Strategic Road Safety

Nationwide Speed Mft Framework NZTA