Evaluating Highway Traffic Safety: An Integrated Approach

Table 2

Definition of the indices that affect traffic safety.

Index; Category	Index; Name	Designation	Unit
Planning indices	Functional grade	FG^a	-
	Highway classification	HC	-
	Land use	LU	-
	Service level	SRL	-
Alignment indices	Straight length	SL	m
	Grade length	GL	m
	Horizontal curve radius	R	m
	Sight distance	SD	m
	Longitudinal gradient	G	%
	Superelevation	e	%
Intersection indices	Intersection density	D	Intersections / km
	Sight distance	S	m
	Intersection Type	Type^b	-
General indices	Road width	RW	m
	Pavement drainage	PD	-
	Climatic condition	C^c	-
	Truck proportion	T	%

Functional grade, a principle grade designed by the Chinese Highway Management Institution, reflects the service level provided by the highway. It is a surrogate measure of traffic volume.
This is a nominal variable that is equal to 1 for nonsignalized intersections and zero otherwise.
This is the climatic condition at the time of the crash.