KiwiRAP

Road Protection Score

Star Ratings are derived from a Road Protection Score (RPS); this risk score is determined via evaluation of each of the road’s design elements. For example, the risk of being involved in a crash on a road with no sealed shoulders is greater than on a road with wide sealed shoulders of 1.2-metres or more).

Using the three primary crash types (run-off road crashes, head-on crashes and intersection crashes), the RPS is calculated for every 100-metre section of road.

Star Ratings have been presented in map form and tables in this report. Since risk scores and therefore Star Ratings, often fluctuate over a given length of road, the predominant Star Rating is assigned to each given section of road.

The Risk Worm graph below shows a 70-kilometre stretch of road from Bombay, south of Auckland, to Hamilton. The blue line denotes the 100-metre sections and the pink line shows the predominant Star Rating for each five-kilometre segment.

The graph shows that the first 30-kilometres of road is rating highly with a predominately 4-Star Rating. However, from 32-kilometres through to the 70-kilometre mark, this falls to a 3-Star and then poor 2-Star Rating.

Risk Worm

State Highway 1 – Bombay to Hamilton

Star Rating bands

The Road Protection Score rating bands in the table below describe the typical features found within each Star Rating.

Rating scale

Description of features

Divided road

Undivided road

5-Star
*****

Straight with good line marking, wide lanes and sealed shoulders, safe roadsides and occasional grade separated intersections. Roads with a local, minor or major at-grade intersection cannot achieve a 5-Star Rating.

No undivided road can achieve a 5-Star Rating.

4-Star
****

Deficiencies in some road features such as lane width, shoulder width or roadside hazards.

Straight with good overtaking provision, good line marking and safe roadsides. Such a road will not achieve a 4-Star Rating if it has high traffic volumes.

3-Star
* * *

Major deficiencies in some road features. These may include poor median protection against head-on crashes, many minor deficiencies and /or poorly designed intersections at regular intervals.

Deficiencies in some road features such as alignment, roadsides, and /or poorly designed intersections at regular intervals.

2-Star
**

Many major deficiencies such as poor alignment, poor roadside conditions and median protection, and poorly designed intersections at regular intervals.

Major deficiencies in some road features such as poor roadside conditions and /or many minor deficiencies such as insufficient overtaking provision, narrow lanes, and /or poorly designed intersections at regular intervals.

1-Star
*

Poor alignment, in mountainous terrain, narrow lanes, narrow shoulders, severe roadside conditions and many major intersections.

Poor alignment, in mountainous terrain, narrow lanes, sealed shoulders, poor line markings and severe roadsides conditions.

Examples of Star Ratings

The following images show what 1-, 2-, 3-, 4- or 5-Star roads may look like. They also explain why that particular stretch of road has been allocated its Star Rating.