Engineering Solutions to Enhance Traffic Safety Performance on Two-Lane Highways

Table 4

Assessment criteria for potential crash hotspots on G109, Beijing.

Categories	Indexes	Units	Class 2	Class 3
Sharp curve	The horizontal curve radius	m	≤ 125	≤ 60
Heavy gradient	The longitudinal gradient	%	≥ 6.0	≥ 7.0
Continuous downgrade	The longitudinal gradient	%	≥ 4.5 (≥3 km)	≥ 5 (≥3 km)
Bad sight distance	Decision sight distance	m	≤ 150	≤ 80
Bad clear zone	The height of slope	m	≥ 4.0
	The distance to shoulder border		≤ 3.0 (Lakes, rivers, swamps, ditches)