Table 2: External factors and explanation.

VariableNameTypeExplanation

Effective widthContinuous variableThe effective width of bicycle lane
Travel speedContinuous variableThe average travel speed for the survey internal
Car volumeContinuous variableCar volume in the adjacent lane (veh/30 s)a
Curb parkingBinary indicator1 if there are curb parking cars along the bicycle lane, 0 otherwise
Retrograde motionBinary indicator1 if there are retrograde bicycles in the lane at the
observed interval, 0 otherwise
Safe gapBinary indicator1 if the adjacent lane is clear of moving car, 0 otherwise

a“veh” is the abbreviation of vehicle.