Curve Widening: Methodology
Curve widening can be accomplished easily and in accordance with AASHTO 2004 by just a couple of clicks. Below is the procedure:
- You must have a valid autoshape input file. The input file is used to determine the curve radii and transition stations where the widening is to be drawn.
- Open the MicroStation design file (plan file) that your Project Manager "run" will be looking for concerning widening elements.
- Invoke Design and Computation Manager, and double click on
the "item" Curve Widening (with transitions) from the MVBA
Applications category, as shown below:
The Draw Curve Widening dialog will appear, as shown below:
Using the browse icon, (the little magnifying glass), select the autoshape input file, and click on Open, as shown below:
The shape input file and it's path will populate the upper dialog field as shown below. Notice that the Job Number, Chain name, Roadway Width, Design Speed and Superelevation eMax values are all populated for you. This is just an informational feature to show you what is being loaded into the application.
The next option on the dialog is how to apply the curve widening. You have 2 options:
- Only Along the Inside Edge of Travel Way
- Divide Equally between Inside and Outside Edges
AASHTO 2004 states "On simple (unspiraled) curves, widening should be applied on the inside edge of the traveled way only. On curves designed with spirals, widening may be applied on the inside edge or divided equally on either side of centerline". Ref: 1st bullet, page 214.
AASHTO 2004 further states, "Preferably, widening should transition over the superelevation runoff length, but shorter lengths are sometimes used". Ref: 2nd bullet, page 214.
If the second option is selected, Divide Equally between Inside and Outside Edges, the application is intelligent enough to know not to divide simple curves without spirals. If the application finds a curve without spirals, even though you may have the option set to divide the widening, these simple curves will only have the widening drawn on the inside edge.... Very cool!
The next option is Disregard Widening < 0.6m (in the case of a US Customary design, you would see < 2.0 ft. here).
AASHTO 2004 states, "It is suggested that a minimum widening of 0.6 m [2.0 ft] be used and that lower values (less than 0.6m [2.0 ft]) may be disregarded. Ref. last paragraph, page 210.
NOTE: You should always toggle this option ON as shown below:
The next option is Additional Widening. If additional widening is desired beyond the calculated curve widening, toggle this option ON and type in the additional widening value.
You have the option to temporarily display the graphics. If this is desired, toggle on Display Only. Remember, if you use this option and then zoom in or update the view, the graphics will not be visible.
The next option is to Generate Report. This option, when enabled, creates a .csv file containing the station ranges curve widening values and transition in/out distances.
This report can be opened using Excel. The text parameters and border symbologies can be formatted in Excel and pasted into MicroStation using Axiom Office Importer. If Axiom Office Importer is not installed on your computer, please contact the Help Desk.
Samples of both the raw and formatted curve widening report are illustrated later in this documentation. To jump immediately to these illustrations, click here.
NOTE: This report is now a requirement in all plan sets.
The final option is Vehicle Type. Use the "drop down arrow" to select from several Vehicle Types.
Before clicking on Draw Curve Widening.... you must select the D&C Manager item and toggle ON Place Influence, in order to set the symbology of the widening element. The example below illustrates using the item that will extend the pavement using the same cross slope as the superelevation shape:
You are now ready to click on Draw Curve Widening as shown below:
You should now have all the appropriate curve widening drawn into your MicroStation design file and at the correct symbologies. Text will also be drawn at each curve location illustrating the amount of widening drawn and whether the curve is less than the minimum radius.
Generate Report option:
When Generate Report is enabled and Draw Curve Widening is pressed, the Save Report As dialog appears as shown below:
An example of what the initial raw report might look like is shown below:
An example of how the formatted report might look like is shown below:
The final step is open the MicroStation design file where this report (or table) is to be placed, invoke Axiom Office Importer, copy the cell range from Excel and paste it into MicroStation.
NOTE: For the exact element symbologies and parameters, such as fonts, text heights/widths, weights, etc... please see the WFLHD Standard Format for Plans.