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Research Report 065 Retroreflectivity: A recommended minimum value

Published: | Category: Safety, security and public health , Research programme , Research & reports | Audience: General

Roadmarkings are provided on roads to give guidance of the route ahead. To be effective at night-time, roadmarkings need to have adequate retroreflective properties. A recommended minimum value of retroreflectivity was established that is appropriate for roadmarkings used on New Zealand roads. This minimum reflective value is 90 mcd.m¯².lux¯¹.

The study method was a panel type, whereby a group of five roading professionals using a Delphi procedure reviewed photographs and video records of six sites, then identified the sites that they judged had roadmarkings of the minimum acceptable level of retroreflectivity. Cross-reference was made to the values of retroreflectivity measured at this site (using a Mirolux 12 retroreflectometer). These measured values were taken as the recommended minimum retroreflectivity value for roadmarkings.

Recommendations were made to determine the performance of existing roadmarkings relative to this minimum value, to develop appropriate test criteria for minimum retroreflectivity values that can be included in roadmarking material specifications, and to extend the principle of a minimum retroreflective value to other materials used for road signs and delineation devices.

Keywords: Minimum performance levels, New Zealand, night-time visibility, retroreflectivity, retroreflectometers, roadmarkings, visibility

Publication details

  • Author:
  • Published: 1997
  • Reference: 65