@Krishna Bejawada? - I've tried to provide some answers below:
(a) Can we edit the ERM dataset? In it's present form, ERM Data cannot be edited by the users. You may use the Persistent Updates option to make the engine prefer/avoid any particulars segments. Umesh can tell better about this.
(b) I would like to know how we can add extra road type.. Can we keep a new road type like railway crossing for few segments of the national highway ? Presently, if a new Roadtype is required to be added to the ERM Data, it should be done in the raw data, which then needs to be built into ERM binary files. We'll also need to first check if the required roadtype information is available in the source data or not. For your question about the railway crossings, we do have railway lines available with us in the source data and some more associated attributes. We'll need to check this further...looks like we can dig the railway crossing segments out with some further research.
(c) If Yes, How do we find those roads and edit the specific link and change the type of that link ? Data-wise, there are various ways of identifying such railway crossing segments. We can either assign a particular roadtype to these. We could also have an extra logical attribute like RAILWAYCROSSING and set it to True/False. We could also add a particular 'railway' specific restriction to the data. Engine-wise, we;ll need to check with the software folks how they would like to approach at it.
(d) If we are successful at editing and giving the new type for the road link. Can we see those road types while we set the priority or avoid list in ERM ? Currently, the engine does identify Toll Roads (by means of a logical True/False attribute) and respects certain types of restrictions too. So, I am sure if the right kind of data is available, the software team should be able to update the engine to be able to handle railway-crossings. However, again, Umesh or Balkrishan (from ERM team) would be the right people to comment on the software parts.
Also, you should be able to get a lot of guidance @Dr. Nishant Sinha? , the PM for Routing portfolio, esp regarding future possibilities!
Hope this helps!