Following are the steps to convert the AutoCad elements to MX strings using the MXConversion option: 1. From the CAD menu, select 'File > Reference', from the 'References' dialog box select 'Tools > Attach' then select the AutoCad file to attach as a reference. Now, from the 'References' dialog box, go to 'Tools > Merge into master', give a data point in the view, and hit OK for the message.
2. Select the element that you want to convert to MX string.
3. From the MX menu, go to 'View > Toolbars > MX Conversion', if the option is checked marked it should already be docked, if not then select the option to activate the tool bar.
4. Select the model in which you want the MX string from the first drop down, and select the 'Feature Set' from the second drop down, in this case Road Centerline. Note: the feature sets will depend on the style set applied to that model.
5. A message will display to confirm the conversion, hit yes. The AutoCad element will be converted to MX strings.
Hope this helps. Do let me know.