Transition from 3 to 4 aspect - Junction signalling

[NJK]

Dear Members,

Is transition from 3 to 4 aspect possible in junction signalling ?

Kindly clarify. Thanks in advance.

Regards,
NJK

[PJW]

Absolutely- it has to be!
If some of the railway only necessitates 3-aspect but some of the railway needs to be 4-aspect unless transition were possible then the whole railway would have to be provided with 4-aspect and that would be a very poor solution- excessive initial cost and ongoing maintenance burden.

Perhaps your question should have been phrased: "How can it be achieved?"

There are several posts on this website that should help you.
Look at the various attempted aspect sequence charts for the past papers and the comments raised on them.

Also if you look at
http://irseexam.co.uk/thread-974.html
you will find links to some Powerpoint presentations you can download that should be helpful. In particular, look at the one rehardng aspect sequence and headway. I haven't got time to find the exact reference now but I am absolutely sure that this is discussed at length within the Module 2 Exam Study Pack.

Actually there is now quite a lot of material on this website, but I admit that it takes some effort to locate. However it is always worth using the Search facility in the top bar in the Green are underneath the title; typing "transition" in there has produced around a dozen hits and just looking at the titles of the threads it produced I think that about three quarters would indeed be the sort of thing you want regarding aspect sequence transitions.

Also remember that to find attachments I have made a thread with an Excel spreadsheet of these. It reminds me that I probably ought to update this again, but actually not much has been added to the website recently (it seems that the 2012 exam students have not been particularly active or are using other methods than this Forum) so in reality there won't be many missing from this listing.

Dear Members,

Is transition from 3 to 4 aspect possible in junction signalling ?

Kindly clarify. Thanks in advance.

Regards,
NJK

[Peter]

I have been asked the following question

I have some doubt regarding junction protection signal that which type of signal aspect should we use at junction 3 aspect or 4 aspect? which one would be best option.

If I opt 3 aspect signalling in that case at junction I need transition from 3 to 4 aspect signalling.

There is some relevant information linked in the posts above, but put simply, it depends on the situation.

You will need to provide an appropriate system for both lines - the appropriate number of aspects for each of the two lines that come together at the junction.

Depending on the relative speeds of the two lines or the points at the junction, moving from, say, 3 to 4 aspects may be simple with a 3 aspect junction signal because you may have full braking between it at Y and the next (4 aspect) signal at R. If the layout allows higher speed, then following a standard 3-4 aspect sequence transition before the junction (having a YGY signal at about half braking distance between the last 3 aspect signal and the first 4 aspect signal (probably the junction signal) signal may be needed.

Please let me know if this does not answer the query.

Peter

[naina.dubey]

Thanks Peter, now my doubt is clear.