Publishing in a Procedia journal versus a 'proper' one I’m torn between asking for my (somewhat weighty) conference paper to be included in an issue of Transportation Research Procedia, versus submitting it separately to a journal with an impact factor, e.g., Transportation Research B. The conference paper will have to be peer reviewed to qualify, but the journal advice says,


  The Transportation Research Procedia does not have, and is not eligible for, an Impact Factor as it does not publish primary research, full length, peer-reviewed articles.


Is a separate submission likely to be worth it (i) for dissemination of the research, and (ii) for REF (Research Excellence Framework) return?
The journal information site says the following:

What is the Transportation Research Procedia?
The Transportation Research Procedia is an open access product focusing entirely on publishing full sets of conference proceedings, enabling fast, world-wide dissemination so that conference delegates can publish their papers in a dedicated online issue on ScienceDirect. (see link: Website)

Which means that this is actually NOT A JOURNAL. And, essentially not equivalent to a journal in any sense. It publishes the proceedings of the recently organized conferences in the related fields. Simply put, it indexes online the papers which are accepted and presented in the conferences.
Why it can not get an impact factor?
Actually, it can not; because, it is not a single proceeding. It is a collection of multiple proceedings. Say for example, International conf. on Transportation Engineering A, International Conf. on Civil Aviation (these are just names, ignore).
Even if it tries to get any impact factor, then it would be completely biased given the number of conferences and their corresponding standards of accepted papers.