The time of concentration method that the Oklahoma Department of Transportation specifies that we use is not one of the methods that are currently available within the OpenRoads Designer Drainage and Utilities software. Currently this is the only thing within our hydrology workflow that we cannot do within the software causing us to have to manually calculate the time of concentration and manually define that calculated time of concentration in the utility properties. It would be fantastic if the Oklahoma Department of Transportations time of concentration method could be added as an option within the software or if there was a way that we could add our own custom equations into the program. I have attached the relevant pages from their roadway drainage manual that contain the formulas they use below. Thank you!