| 4. | The coefficient of retro-reflection R' of the retro-reflective areas, when measured after a recovery period of 48 hours as specified in Annex 7, at an entrance angle of β2 = 5° and an observation angle of α = 20', shall be not less than the value in Table 9 or more than the value in Table 10 respectively. Before measuring, the surface shall be cleaned to remove salt deposits from the saline mist. | a0c0 |