When working with design speed labels within Civil 3D, you may have noticed that the application displays Imperial speeds as "mi/h" with seemingly no way to change it to display MPH, or any other speed abbreviation for that matter. If you were to look through the drawing settings abbreviations, you will find that there is no abbreviation that drives this speed unit value. If this issue is familiar to you, this blog post will help you get the design speed unit value you require on your projects.
To start, switch over to your Settings tab of your Toolspace and expand the alignment tree, and dive down into the alignment labels for Design Speed. Under the Design Speed tree, you will find Expression within it. Right-click on the Expressions, and choose New. Within the New Expression Dialog, name the expression we are creating. In the figures below, I used MPH to name this expression, but you can name it Speed or any other name as this technique can be used for any speed unit type. After giving this expression a name, add the {Design Speed} property tag by clicking on the Properties button found just to the bottom-right of the Expression field. Once the {Design Speed} property tag has been added to the Expression field, close the New Expression dialog. A new expression should appear in the Design Speed label tree denoted by a black dot to the left of the Expressions. Clicking on the Expressions will expose all expressions present for this category below in the details pain. Right-clicking on an established expression within the Details Pane at the bottom of the Toolspace, Settings tab will allow you to edit existing expressions.
Now that the new expression has been created, it can be utilized within any Design Speed label the same as any other property that can be added to the label via the Text Component Editor. Note when using this expression, the return will only be the raw design speed, allowing you to hard code the unit value you require. In my example, I followed up the expression property with MPH.
Once the label has been established, utilize it like any other Alignment label, including in Alignment Label Sets.
This is a simple solution, that may not be apparent, which should help you with displaying the speed unit values that you require rather than relying on the default design speed unit values provided with the Civil 3D application.
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