06-02-2016, 03:35 PM
(03-02-2016, 10:03 AM)dorothy.pipet Wrote:(17-06-2009, 04:48 PM)JPM Wrote: Here is the worked example of the question that we went through yesterday.
An attempt for comments please.
This was done with no time limit, and books open; I had a few more ideas but stopped at one page as I wasn't sure how much I'd have got down under exam conditions.
I think the format of presentation worked very well.
1st row. Traction interference. Definitely right that in the modern traction world, track circuits are difficult- not insuperable but have to be increasingly complex so certainly a disadvantage. Rather naïve to think that axle counters are not vulnerable; there certainly are issues (they use magnetic fields around the running rail and typically have potentially sensitive electronics in close proximity after all), but you are correct that in general the current equipment is adequately designed to be relatively immune. I have no direct experience of on-board but again I doubt it is as easy and clear cut as you suggest; at least the positioning of the potentially sensitive equipment it is a fixed known configuration with the traction equipment on board the train and so is a problem that can be solved.
2nd Row. I took this to be the vehicle-infrastructure interface definition.
There are some compatibility issues with axle counters (e.g. wheel size, axle spacing) and obviously any system whereby the train reports its position relies on being able to communicate that information back to the infrastructure in a safe manner and indeed relies upon some absolute position references in order that oometry is sufficiently accurate in critical areas. Therefore the "not requireds" rather over-optimisitic!
3rd Row. Broadly agree
4th Row. Agree.
5th Row. Agree.
6th Row. Might have been better to treat recovery after possession and power failure separately.
Its the same for track circuits (i.e. neither a problem), but rather different for the others.
The real issue for train positioning purely relying upon info from the trains is when communication is lost. It is bad enough if it is just one but if there is a failure and you need to reinitiate the railway without even knowing how many trains there may be out there is when it gets horrible!
Do cover this a bit in row 8, but not to this extent; also should have considered tunnels etc both for impact on radio transmission and any GPS utilisation since clearly need to use an alternative and therefore there could be safety risks associated with boundary / transition.
7th row. Agree
9th row. Probably better titled Train Integrity (initially I read it to be about the limit of train detection area!)
I think that overall this was a very good answer to the question with a lot of content in a compact presentation
PJW