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I had the opportunity to assist a customer recently with their experiencing some issues with a marked point targeting assembly. When used on something like a divided crowned highway, it forms part of some of the more interesting or advanced assemblies to construct.

After investigating, experimenting and reading up on these sub-assemblies and their use, I took it upon myself to reverse-engineer one of the most fun roads I know to navigate. Set against the slopes of a mountain, there is a divided crowned highway, each side of which is a dual lane that follows its own alignment and its own profile.

Firstly, we recognize that the base of the subassembly followings a sacrificial assembly and profile (in the case where each of the sides follow their own alignments and profiles, the base alignment and profile serve only to have the corridor exist and serves no other design purpose).

Next, we observe that the left crown and the right crown are positioned some distance away from the base assembly by the Generic LinkWidthAndSlope subassemblies. These subassemblies can take profiles and alignments as width and elevation targets, which makes them perfect for positioning the crowns. However, they must not form a part of the corridor for quantification or surfacing. Do this by setting the “Omit Link” property of the LinkWidthAndSlope subassemblies to “Yes”

The and the left side groups of the assembly is now created with the crowns at the LinkWidtAndSlope points. The slope and width of the LinkWidthAndSlopes do not matter in this case because they are going to be targeted to slave the crown to a specific alignment and profile anyway.

Then you also want to place a marked point at the left of the right hand assembly group (or right of the left side assembly group if you want to target to the left instead).

Now use the LinkToMarkedPoint subassembly on the left grouping to target the Marked on the right grouping.

It is at this stage when you may set the LinkWidthAndSlope property “Omit Link” to “Yes” on both the left and right grouping. Note, you will be able to target them to the relevant alignments and profile even when they are omitted as links.

The next thing to do is to set the relevant superelevation properties of the subassemblies.

Use Superelevation Slope = Right Outside Shoulder

Shoulder Slope Direction = Away from Crown

Use Superelevation = Right Lane Outside

Shoulder Slope Direction = Away from Crown

Potential Pivot = Yes

Inside Point Code = Crown

Outside Point Code = Edge of Lane (Lane)

Use Superelevation = Right Lane Inside

Shoulder Slope Direction = Away from Crown

Potential Pivot = Yes

Inside Point Code = Crown

Outside Point Code = Edge of Lane (Lane)

Use Superelevation Slope = Right Inside Shoulder

Shoulder Slope Direction = Away from Crown

The left assembly grouping’s subassemblies follow the same naming pattern and superelevation properties.

After creating the corridor, the targeting of the subassemblies is easy enough, provided you have the alignments and profiles for the crowns, and the alignments for the width of the lanes and the shoulders.

We only use three profiles. One is for the left crown which is a proper design profile. The same goes for the right crown profile. The sacrificial base profile is simply for creating the corridor in the first place.

Once the corridor is properly targeted, we must apply superelevation.

I recommend you then use the Superelevation Wizard to perform superelevation calculations.

Roadway Type = Divided Crowned with Median

Pivot Method = Centers

Median Treatment = Distorted Median

2-lane symmetric.

Shoulder control.

Set the attainment method.

The more lanes you use, the bigger the factor is that is applied to the transition length, as can be read in this discussion.

“With respect to the transition length table, I suggest that you read Chapter 3, 3.3.8.2 “Tangent to curve transition” of AASHTO 2018. Once you do it you’ll get a sense of how the transition length changes depending on the number of lanes rotated.

I guess C3D gives us just the 2 and 4-lane options because those are the most used. Anyways, regardless of the transition table as designers, we know we end up adjusting the whole diagram depending on our needs and any of the outcomes is a good start.”

Here we can see the superelevation being applied in section (x5 vertically exaggerated). The left and right groups superelevated to impart a normal component to the vehicle reaction forces (making the vehicle “hug” the corner).

Here is the overall result. I zoomed in and investigated most of the length of the corridor and I am satisfied that the result. The finer one sets the frequencies around the bends and the straights the smoother the result. Shown at the end is the clear definition of the roadway. Everything looks to be working as designed.

If you need help adopting the AEC Collection or the Autodesk Construction Cloud in your practice or you are looking to invest in hardware, please contact Micrographics so that we may be of assistance.