2 + 1 Highways: Overview and Future Directions

Table 9

Proposed classification of 2 + 1 highways.

Characteristics		Class
		I-a	I-b	II-a	II-b	III
Alignment	Could be divided in the future	Yes	No	No	No	No
	Target speed (km/h)	100	100	Variable	Variable	Variable
Number of lanes	Continuous three lane	Yes	Yes	No	No	No
	Alternating 2 + 1 and 1+1 sections	No	No	Yes	Yes	Yes
Cross section	Can be widen without restrictions	Yes	Yes	Yes	Yes	No
	Limited widening (1 m)	No	No	No	No	Yes
Left turns	Intersections	No	No	Yes	Yes	Yes
	Roundabouts	No	No	No	Yes	Yes