Four-lane undivided cross-sections have reduced safety and operational performance compared to other alternatives and should be avoided. lists preferred optimized cross-sections for various combinations of volume, driveway activity, and truck percentage. Conversion of a two-lane highway to a four-lane highway facility should include a median when possible. If an existing two-lane highway has rolling terrain or restricted right-of-way conditions that affect the feasibility of widening to a four-lane divided highway, conversion to a Super 2 highway, a two-lane highway with TWLTL, or a Super 2 with TWLTL may be considered to improve passing opportunities and traffic operations. , , and include the general geometric typical section features for four-lane highways.

Before converting the existing two-lane roadway, a crash analysis should be conducted to identify specific areas with high crash frequencies so that corrective measures can be taken where appropriate. See for additional information on roadway cross-section optimization and Super 2 design.