How to assign different roadbed layers by zone?

Summary

In the templates of MDT, roadbed layers are assigned per platform vector, so that each zone (roadway, sidewalk, curb, hard shoulder, berm...) can have its own package of thicknesses and materials. This article explains how to make that differentiated assignment, how the overlap works in order to apply different materials on the hard shoulder or the berm, and how to solve the most common problems: the "Roadbed layers" dialogue that does not open, "undetermined" vectors that leave the volume calculation at zero, layers that cannot be left empty, and steps in the transition between the sidewalk and the road.

Applies to

• MDT — Professional version. The documented cases expressly mention MDT 25 Professional; the remaining enquiries do not state a version. In MDT26 the reference manual documents roadbed layers and their overlap with the same behaviour, with one important proviso: it states that the definition of roadbed layers «only affects vectors of type lane, hard shoulder and berm». The procedures in this article that refer to the sidewalk and the curb come from cases solved by support on MDT 25: if you work in MDT26 and the program does not let you assign roadbed layers to them, follow what the manual for your version states and consult Aplitop technical support.

• Templates functions (definition of platform vectors and roadbeds).

Symptoms

• You need to define different roadbed thicknesses and materials for the roadway, sidewalk, hard shoulder or berm, and cannot find where to do it.

• When applying different roadbed thicknesses, no thickness appears on the roadway and it cannot be assigned.

• When clicking on an element (for example, the curb), the "Roadbed layers" option "flickers" but the dialogue never opens.

• The calculated roadbed layers are not parallel to the grade line or have odd shapes, and the measurements of some material do not add up.

• The roadbed layer volume calculation returns zero.

• In the transition between the sidewalk and the road a step appears that does not match the roadbed packages defined.

• You cannot get a single material (for example, aggregate) applied on the berm instead of the full roadway package.

Cause

Roadbed layers are defined on the platform vectors of the template and cover the width of each vector. The problems above are due, depending on the case, to:

• Not having defined the roadbed layer in the assignment made, or trying to open "Roadbed layers" on a vector that has no value assigned yet.

• Platform vectors defined as undetermined (I3, I2... D2, D3), to which the roadbed definition of the "Roadbeds" tab is not applied.

• Not using the overlap when a different material is wanted on the hard shoulder or the berm (a defined roadbed layer cannot be left empty).

• Vectors with value 0 on one side of the section, or no package defined on the curb, which causes the step in the transition.

Solution

Case: assigning different roadbed layers to the roadway, sidewalk or other elements

1. In the template definition, define different roadbed layers for each zone: the sidewalk vectors, the auxiliary vectors and the running surface vectors each have their own definition.

2. For a specific element of the platform (for example, the sidewalk): select it, press the right button and choose Assign roadbed layer.

3. For different thicknesses or materials in cut and in fill, define two different sidewalk vectors in the platform (one for cut and one for fill) and, in each of them, edit it by double-clicking to state whether it applies in Cut or in Fill. Do not assign the same material separately to cut and to fill on a single vector: it would be counted twice in the measurement; in that case use "Both".

Case: the thickness is not shown or the "Roadbed layers" dialogue does not open

1. If, when applying different thicknesses, the roadway is left with no thickness and it cannot be assigned, check the roadbed assignment made: the roadbed layer is missing within that assignment.

2. If, when clicking "Roadbed layers" on an element (for example, the curb), the dialogue does not open (it flickers and nothing appears), the cause is that this vector has no value assigned. Assign a value to the vector first: the minimum value the program accepts is 0.005, but to avoid rounding errors and overlapping sections on tight curves it is advisable not to go below 0.01–0.02 m. The value refers to the dimension of the vector in the table, not to the vertical dimension.

3. Place the cursor on the cell where you assigned the value, press the right button and select Roadbed layers in the menu.

Case: step in the roadbed transition between the sidewalk and the road

1. Check that you have no vectors set to 0 on the affected side of the section: there must be a minimum vector. The minimum value the program accepts is 0.005, but to avoid rounding errors and overlapping sections on tight curves it is advisable not to go below 0.01–0.02 m.

2. Define the roadbed package on the curb as well: if the curb is left with no package, the transition between the sidewalk package and the road package produces the step.

Case: checking the extension of a vector (widening) up to a polyline

Once the polylines have been assigned to the vectors, there are two ways of checking that the assignment has been made correctly:

1. In the Templates window itself, at the top of the display, open the Plan view tab: there you can see how the result looks.

2. Or draw it in the CAD: once the segment has been generated, run Roads/Segments > Generate Proposed Terrain.

To assign material layer thicknesses on the lanes (not only on the sidewalks), the procedure is the same as in the first case: define different roadbed layers for the sidewalk and for the running surface.

Case: applying a different material on the hard shoulder or berm — how the overlap works

A defined roadbed layer cannot be left empty: a material must always be applied to it. So that the full roadway package does not extend into the berm or the hard shoulder, the overlap of each layer is used:

1. What the overlap is: it is the amount of material from a layer defined on the roadway that extends (overlaps) into the hard shoulder or berm area. The rest of the width keeps the different material defined on that tab, and is distinguished in the roadbed layer measurements.

2. Overlap material: specify the material so that it can be identified in the measurements (for example, in one documented case the overlap was applied on the 2 upper layers of the berm with the material "Hard shoulders").

3. Overlap distance: it is the distance the material continues from the lane into the hard shoulder or berm. For example, with 0.5 m the roadway material extends the first 0.5 m into the hard shoulder or berm.

4. Beware of the value 0: if you enter 0, the program understands that there is no overlap and applies the roadway material on the whole vector. Therefore, if you want the hard shoulder or the berm to be almost entirely of another material (for example, lane with asphalt and berm with aggregate), do not type 0: enter at least 0.01 m, so that the whole hard shoulder or berm is filled with the other material except for that minimum overlap.

5. Slope: it is the slope applied to the overlap; you can enter a value of 1/1 or the same one as the roadbed layer.

Case: "undetermined" platform vectors break the roadbed calculation

If the calculated layers have odd shapes, the measurements do not add up or the roadbed layer volume comes out as zero, check the type of the platform vectors:

1. If the vectors are defined as undetermined (I3, I2... D2, D3), the roadbed definition of the "Roadbeds" tab is not applied to them.

2. Press the right button on each column and change the vector type to lane, berm or hard shoulder.

3. Alternatively, press the right button on each undetermined element of the vector and apply the roadbed layers one by one.

4. If, because of the composition of the platform, you cannot avoid an undetermined vector (for example, after a sidewalk), type the thickness of each layer manually; the volume will not be calculated automatically and the layer will not be extended.

Case: removing an unwanted selected soil layer from the roadbed package

In the documented case, the simplest way indicated by support was:

1. Cancel the selected soil in the roadbed tab.

2. Add a layer directly in the roadbed package with the thickness needed (0.32 m in that case) and a similar material.

3. Modify the slopes so that they start from the foot of the roadbed.

If the problem persists

• If materials appear counted twice in the reports, it is not an unsolved case: check whether the same material has been assigned separately to cut and to fill on a single vector, as explained in step 3. Other related measurement questions (for example, when to use "singular vectors" instead of "all vectors" in roadbed layer measurements) have no documented answer in the cases behind this article: if you are in that situation, contact Aplitop technical support.

• The support team has videos showing the complete procedure for defining roadbeds by zone, made even on the customer's own segment: attach your segment when opening the enquiry.

• See also What is "Roadbed Layer Overlap"? if you need to assign a different material at the ends of the roadway (Outer Shoulder and Berm vectors).

Category: Templates and roadbeds · Level: Intermediate