(16-09-2010, 09:26 AM)greensky52 Wrote: In part b2, why do you think it means 3 aspect at 2010m spacing?
According to the calculation, 3 aspect can not fit for the requirement. Min signal spacing means the distance between any two signals, or between Red and Green signal? If take 4 aspect and signal spacing as 0.5*BD, isn't it the min spacing?
I agree that 3 aspects would not meet the headway requirement specified on the notes of the layout. It depends if you read the question paper itself literally. I think that you could perhaps make a case for interpreting "at minimum spacing" to be "at minimum spacing that not only respects the braking but also the headway requirement" but you did not state that as an assumption.
The wording of the question referred to the categories of traffic and speed but certainly did not mention capacity / headway and therefore I read into the wording is that this was deliberately not to be included within the consideration.
The fact that other bits of your answer seemed to be following the pattern of an approach which was suitable to other years rather than what was requested on this occasion, adds to the view that the examiner is likely to form. That is why you need to be very careful to state your interpretation when a question seems a bit ambiguous- apart from anythhing else it demonstrates that you have read carefully and are trying to answer
PJW