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Table 2 List of explanatory variables, with their symbol, unit and data source
From: Safety assessment of Czech motorways and national roads
Element type | Symbol | Variable [unit] | Data source a |
|---|---|---|---|
Interchange conflict points | AADT | Annual average daily traffic [veh/day] | NTC + own survey |
Type | Type of conflict point (merging, diverging, etc.) | online maps | |
Signal | Traffic control device (unsignalized/signalized) | online maps | |
Channel | Channelization by road marking (no/yes) | online maps | |
Directions | Number of driving directions | online maps | |
Interchange ramps | AADT | Annual average daily traffic [veh/day] | NTC + own survey |
L | Length [m] | RMD | |
Ramp | Type (on-ramp, off-ramp, etc.) | online maps | |
Curve | Horizontal curvature (straight/curved) | own GIS | |
R | Horizontal radius [m] | own GIS | |
Sections between interchanges | AADT | Annual average daily traffic [veh/day] | NTC |
L | Length [km] | RMD | |
Access | Number of accesses per kilometre | RMD | |
Parking | Number of available parking space | RMD | |
Intersections on national/secondary roads | AADT | Annual average daily traffic [veh/day] | NTC |
Location | Location in rural/urban areas | online maps | |
Control | Traffic control device (yield, stop, signals) | online maps | |
Bypass | Bypass lane (no/yes) | online maps | |
Turn | Turning lanes (no/yes) | online maps | |
Legs | Number of roundabout legs | online maps | |
ICD | Roundabout inscribed circle diameter [m] | online maps | |
Island | Roundabout central island diameter [m] | online maps | |
Entry | Average of roundabout entry angles [°] | online maps | |
Deviation | Average of roundabout deviation angles [°] | online maps | |
Circ | Width of roundabout circulatory lane [m] | online maps | |
Apron | Width of roundabout track apron [m] | online maps | |
Sections of national/secondary roads | AADT | Annual average daily traffic [veh/day] | NTC |
L | Length [km] | RMD | |
Urban | Ratio of location in urban areas | own GIS | |
Minor | Number of minor intersections per kilometre | online maps | |
CCR | Curvature change rate [gon/km] | own GIS |