Conditions - Light
From Wiki
Light conditions is a STATS19 field which indicates the conditions at the time and location of a crash. it is represented by a MAST dimension.
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In STATS19
Lighting conditions are recorded by combining the prevailing natural lighting conditions when a crash occurred with the presence or otherwise of systems of stree lighting and whether or not they were operational. Hence, raw STATS19 data provides seven possible combinations of lighting conditions:
- Daylight: street lights present
- Daylight: no street lighting
- Daylight: street lighting unknown
- Darkness: street lights present and lit
- Darkness: street lights present but unlit
- Darkness: no street lighting
- Darkness: street lighting unknown
Darkness is defined as half an hour after sunset to half an hour before sunrise. Daylight means all other times. Scattered or isolated street lamps which are lit are recorded as street lights unlit.
In MAST
Light Conditions is available as a dimension in MAST reports. This dimension contains three alternative hierarchies, representing different possible approaches to grouping the STATS19 data. Users should consider which hierarchy is most appropriate for each report, based on the meaning of the highest levels as defined below.
Crash_Conditions_Light_Daytime hierarchy
Day between half an hour before sunrise and half an hour after sunset
- Day_LightsPresent
- Day_NoLights
- Day_LightsNK
Night between half an hour after sunset and half an hour before sunrise
- Night_LightsLit
- Night_LightsUnlit
- Night_NoLights
- Night_LightsNK
Crash_Conditions_Light_Lighting hierarchy
This is the default hierarchy which is used when the Conditions - Weather dimension is added as a report category, series or filter without a specific hierarchy being selected.
Present a system of street lighting is present at the crash location
- Day_LightsPresent
- Night_LightsLit
- Night_LightsUnlit
Absent no system of street lighting is present at the crash location
- Day_NoLights
- Night_NoLights
Unknown street lighting at crash location unknown
- Day_LightsNK
- Night_LightsNK
Crash_Conditions_Light_IsDark hierarchy
Light Driving conditions were illuminated, by natural or artificial means
- Day_LightsPresent
- Day_NoLights
- Night_LightsLit
- Day_LightsNK
Dark Driving conditions were not illuminated by any means
- Night_LightsUnlit
- Night_NoLights
Unknown illumination uncertain
- Night_LightsNK