Estimating Cross-Slope of roads

I have been working with LiDAR point cloud data to find cross slope of roads using ArcGIS. I want to utilize plane fitting to the points in order to get the cross slope. I have done few steps like I have extracted my region of interest using buffer tool and generated transects with respect to the centerline at certain intervals. However, I am unable to proceed after this step. Can anyone please suggest me how to proceed further?

After creating the transects, I also generated points on those transects. Now I need to get the elevation of these points. I tried running Extract Multi Values to points tool. However, it showed error after running for around 2 hours and stated that your input features do not have any spatial features. Any kind of suggestion or help is truly appreciated.