How to construct back-to-back clothoid transitions?

Question

I need to construct reverse curves with transitions that have a common tangent point, as shown in this standard figure here. 
 I need both arcs to be of 145m radius and the back-to-back spirals to be 25m long. How should I go about doing that? 
 Thanks.

Ross Brown · Answer

Yes you can do this in ORD but best to have the latest version as some of the older versions couldn't do this... I am using version 8.1. ie 2020 release 2 
 So first lay out your first tangent line ie line between points. Then use arc to element NOT arc from element as we usually have to pass thru a point in geometric design. 
 Lock in your 145m radius by hitting the enter key. 
 From there please watch your prompts... you may need to hit the shift key to switch hands of your curve now pick the point you want to pass thru, I usually lay this construct point out via a cad line or an ORD construction element. Then select trim back. 
 Next you will have a tangent that you need to connect your reverse curve to so construct the final tangent line. Use line between points. 
 Now the tricky bit...Use this command.. complex transition from any element and arc it is last one in the bottom of the arc list. 
 So trick with this is what it says any element and arc so pick the straight first.., Not the arc... so pick in the reverse order... 
 When you select this command lock in the offsets of zero first... . Another tricky bit look under the ahead transition look for type pull down from there and choose the type "double spiral" 
 Enter your reverse curve spiral lengths ie 25m. Remember to type in your back spiral of 25m. 
 Then follow your prompts .. back element is the straight ahead element is the arc trim both job done! 
 Let me know if you can follow this workflow otherwise I can record a video for you! 
 Ross