Field of vision (A-pillar geometry) - a review of the needs of drivers: final report.
It is the responsibility of the Department of the Environment, Transport and the Regions (DETR) to improve the safety of the UK road network. Driver vision has been identified as a significant factor and the possible causes of reduced vision require further investigation. This study was commissioned to identify the problems associated with restricted visibility for vehicle drivers, in particular the consequential risk to road safety of changes in A-pillar size and position, driven by the need for improved structural and aerodynamic performance, which can restrict driver vision. The experimental trials supported the findings of the literature review and the driver survey that A-pillars do impede the driver’s forward field of view. It was shown that: • Approximately one third of all the targets presented in the vicinity of the A-pillar were not detected. • A-pillar obscuration is a greater problem in newer, as opposed to older, cars (although this is only statistically significant for viewing past the off-side A-pillar). • If drivers make the effort to ‘look around’ their A-pillars the visual problems caused by A-pillar obscuration can be significantly reduced. However such a strategy cannot be relied upon and may be unsafe to encourage if the driver should also be concentrating on the road ahead. The study therefore shows that there are safety disbenefits due to the trend for wider A-pillars. Further research work into A-pillar design should be considered in terms of the drivers’ field of view which may include: • the use of accident statistics to quantify the effect of A-pillar design on driver vision, • a study to investigate the relationship between target detection and obscuration angle (ranging from 0° to 6°), this may also include an investigation into the location of the A-pillar in the drivers’ visual field, • creating awareness amongst interested parties of the visual effects of increased A-pillar thickness.
Department of Transport