Question:

In MX Road, there is this option in surface analysis for viewing the flow based on the ground surface called flow arrow and I can see that in InRoads there is this option called slope vector. Is slope vector actually similar to flow arrow? How do I get the flow arrow analysis inside InRoads?

Solution: 

Here are two options to view the flow of your surface with flow arrows.

Evaluation>Hydrology and Hydraulics>Trickle (Hydrology and Hydraulics is an Application Add-In, Tools>Application Add-Ins> Hydrology and Hydraulics, this command will be placed on the InRoads dialog box at Evaluation).

The Trickle command dynamically traces the path of a drop of water down a selected DTM surface or up the surface to the water source. You can also display the path or paths at a selected XY location. The path lines are always
drawn from high to low so that you can use your own linestyle to indicate the direction of slope.

Or

Surface>View Surface>Annotate Feature (Slope Direction)

This command annotates the slope direction of a feature in plan view. You can define a cell to use as the arrow, the offset, and the option to annotate at every segment or at a specified interval.