Field and laboratory data have been re-analysed from a number of studies relevant to night driving visibility. For unlit, open road conditions it has been shown that the visibilities of tail-light, disc objects and pedestrian dummies can be related on a single luminance-visual area characteristic. A set of luminance increment-visual area characteristics has been established for predicting visibility under varying conditions of background and glare veiling luminances. For small angles of glare (<100') it was found necessary to use the veiling luminance formula, lv = 9.2 etheta-3.44. Predictions have been made of the required reflective performance of road studs located under street lighting. Various visibility criteria are discussed. Field experiments are also described in which the visibilities of a pedestrian dummy and disc objects of varying size and contrast were measured under dynamic night driving conditions. It was found that a contrast multiplier of 4 was required in applying laboratory 50 per cent probability of detection thresholds to a 'just visible' criterion level of visibility in the field experiments. However, if such laboratory thresholds were to be applied to practical night driving conditions, a contrast multiplier as large as 28 Might be required to allow for factors such as the unexpected appearance of an obstacle to an unalert driver. /TRRL/


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  • Accession Number: 00142754
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Files: ITRD, TRIS, ATRI
  • Created Date: Jul 19 1977 12:00AM