This blog’s entry covers the assembly group’s construction and logic for a 4-way intersection that maintains both roadway crowns. My next blog entry will cover tee intersections that contain offsets.
When creating the intersection assemblies, it is a challenge to determine what assembly configurations are needed to complete the intersection. The assembly configurations are determined by the type of
intersection you are designing. When the intersection is a 4-way and holds both crowns the curb return assembly builds the intersection. See the right side of Figure 1.
The reason for this difference is how the secondary road completes its portion of the intersection. In a 4-way intersection holding both crowns, the curb assembly completes the intersection between the primary and secondary roads. See Figure 2.
Assemblies – Primary Road
The assemblies for the primary road are found in Figure 3. When the intersection is a 4-way and it holds both crowns, the design uses only the Primary Road – Full Section.
The Primary Road Half Sections –Right and Left are used only if the primary road has any widening. Both assemblies must be assigned to the intersection even though they may not be used.
Figure 3: Primary Road Intersection Assemblies
Assemblies – Secondary Road
The secondary road assemblies are in Figure 4.
The last assembly in Figure 4 is the curb return assembly. The curb assembly follows a curb return alignment and creates the intersection. The intersection creation process prefers the right curb assembly.
The Secondary Road Half Section –Daylight Left and Right sections are used when there is a secondary road widening.
With a 4-way intersection with no widening, only the secondary road full section and curb return are used to create the intersection.
Intersection Assembly Assignment
When creating the 4-way intersection, you must assign the correct assemblies. Figure 5 has the assembly assignments for a 4-way Intersection that holds both roadway crown elevations.
Corridor Properties – 4-Way Intersection Maintain Both Crowns
The resulting intersection from a 4-way intersection holding both roadway crowns with no widening uses the minimum number of assemblies. See Figure 6.
Happy intersection designing!