The Challenge

In 2016, the NZ Transport Agency released the Speed Management Framework, setting out how Safe and Appropriate Speeds (travel speeds appropriate for the function, design, safety and use of a road) should be assessed. Road Controlling Authorities (RCAs) were expected to assess the Safe and Appropriate Speeds of their roads and develop a programme of safety interventions for high risk roads where safe and appropriate speeds did not align with the speed limit. 

To support RCAs, Abley developed a process to calculate safe and appropriate speeds for every road in New Zealand. Input attributes were derived from existing datasets using advanced geospatial analytics. The outputs were released to RCAs through the Safer Journeys Risk Assessment Tool (“Mega Maps”), allowing them to identify where safety interventions, such as speed limit reductions, should be prioritised.

The Solution

A geospatial segmentation and assessment methodology was developed using existing spatial datasets. This included modelling land use using a combination of urban/rural boundaries, zoning maps, OpenStreetMap and LINZ topographic layers. Other inputs were derived from the centreline dataset itself, including curvature and intersection density.

In addition to presenting safe and appropriate speeds, infrastructure risk rating (IRR - a road risk measure derived from road stereotype, alignment, lane and shoulder width, land use, traffic volume, roadside hazards, and access and intersection density) is calculated for every road in New Zealand, Mega Maps includes additional contextual layers and enables users to select and export road data, access Street View imagery, and generate template letters for speed limit reviews by selecting roads from a map and entering additional information. 

An additional enhancement in Mega Maps is Engagement and Consultation functionality which involves following a legal process for ensuring stakeholders are correctly notified, including identifying which roads are affected. Mandatory questions and steps ensure users follow the correct process and standardised letters mean that every RCA provides the correct information to stakeholders.

Screenshot Infrastructure Risk Rating

The Outcome

This project supports RCAs by identifying and prioritising roads where speed management will reduce deaths and serious injuries. Mega Maps provides a standardised view of road risk and opportunity, prioritised nationally and regionally. This allows RCAs to focus on implementing high-benefit speed management interventions, rather than spending significant time and effort assessing roads at a local level. This represents a substantial cost saving to RCAs. The Engagement and Consultation Tool also drastically reduces effort and ensures compliance with legislation, with the added benefit of standardising how proposed speed limit changes are communicated nationally.

Mega Maps collates several road safety metrics developed specifically for the local government sector. Without this, RCAs would be expected to do this themselves, and in many instances, this would have been undertaken using non-spatial tools such as spreadsheets, rather than applying a spatially enabled approach to assessing road risk. Being able to overlay multiple measures of risk and contextual layers provides new insights for developing speed management programmes.

New Zealand road users are the ultimate beneficiaries of this project. The implementation of speed management recommendations from Mega Maps could prevent 245 people from being killed or seriously injured annually.

Screenshot Safe and Appropriate Speeds