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.
