bevans
*Site Admin*

bevans
*Site Admin*

bevans
*Site Admin*

X'Trapolis-904M
*Deputy Commissioner*

Belgrave

Suspended • 1 hour agoBetween Bayswater & Belgrave due to a tree that has fallen across rail tracks at Upper Ferntree Gully. Replacement buses are in operation. Please listen for announcements.

Train services have resumed between Carrum and Moorabbin after an earlier issue with fallen trees. Customers may experience delays to 15 minutes as we get our trains and drivers back in position.

Between Macleod & Eltham due to a tree that has fallen across rail tracks at Macleod. Buses replacements may take some time to get in position, please listen out to announcements

Train services have resumed between Ringwood & Lilydale after an earlier issue with a fallen tree across rail tracks at Croydon. Customers may experience delays to 10 minutes as we get trains and drivers back into position.

Delays up to 15 minutes due to a tree that fell across rail tracks at Hampton. Trains need to travel at reduced speed until the area is fully cleared.

The line has reopened between Bell & South Morang after a fallen tree was removed from across rail tracks at Ruthven. Delays to 15 minutes as we recover. Please listen for announcements.

Between Frankston – Stony Point due to a tree fallen across rail tracks in the Tyabb area. Replacement buses will be in operation. Please listen for announcements.

Customers may experience delays to 10 minutes in both directions as a knock effect from the signal issue on the Werribee and Sunbury lines.

X'Trapolis-904M
*Deputy Commissioner*

bevans
*Site Admin*

X'Trapolis-904M
*Deputy Commissioner*

X'Trapolis-904M
*Deputy Commissioner*

X'Trapolis-904M
*Deputy Commissioner*

DalyWaters
*Chief Commissioner*

Valvegear
*Oliver Bullied, CME*

712M
*Chief Commissioner*

raudteejaam
*Train Controller*

Is this the first "once in a hundred years" weather event for this year?

Just to clarify, when people say a "one in one hundred year storm", what it actually means is there is a 1% chance in a given year that the storm/flood/whatever will occur. That's why it's possible to have such events multiple times a year or in successive years, it's a mathematical formula, not a guaranteed weather cycle.

My SES crew are still mopping up today, though we have just cleared our last task. We had a tree leaning against was either a power staunchion or signal gantry on Tuesday that required a lot of back and forth with Metro, who eventually took responsibility for clearing it. I assume they did before it created any problems.

Valvegear
*Oliver Bullied, CME*

Just to clarify, when people say a "one in one hundred year storm", what it actually means is there is a 1% chance in a given year that the storm/flood/whatever will occur. That's why it's possible to have such events multiple times a year or in successive years, it's a mathematical formula, not a guaranteed weather cycle.

Without wishing to appear rude, I do not believe your definition. The words mean what they say, i.e one in a hundred years. That is plain English. Without going into details, I have had this debate with idiot Consulting Engineers, and they believe they are designing for one event, and one only, and it will occur only once in a hundred years. The concept is, of course, nonsense, but enough of them believe it.

xxxxlbear
*Token Booking Clerk*

bevans
*Site Admin*

SAR520SMBH
*Train Controller*

bevans
*Site Admin*

It's on it's way bevans. The wind is starting to pick up here in Adelaide. Forcasting rain to hit around early arvo, gail force winds up to 100kph, hail and possible thunderstorms. Brace yourselves over there guys.

lots of false pics from Bunbury. The wind is picking up.

ZH836301
*Chief Commissioner*

raudteejaam
*Train Controller*

Without wishing to appear rude, I do not believe your definition. The words mean what they say, i.e one in a hundred years. That is plain English. Without going into details, I have had this debate with idiot Consulting Engineers, and they believe they are designing for one event, and one only, and it will occur only once in a hundred years. The concept is, of course, nonsense, but enough of them believe it.

The Bureau of Meteorology backs me up. You can choose to believe them as the experts or not. The phrase is just a phrase, the actual maths and science behind it really means there is a 1% chance that it will occur in a given year. I'm not going to comment further, but you can read the link below and see for yourself.

I'll quote the clearest part for you:

It is important to note that an ARI (average recurrence interval) of, say, 100 years does not mean that the event will only occur once every 100 years. In fact, for each and every year, there is a 1% chance (a 1 in 100 chance) that the event (in this example, 48.2 mm in 1 hour) will be equalled or exceeded (once or more than once).

http://www.bom.gov.au/water/designRainfalls/rainfallEvents/why100years.shtml

Valvegear
*Oliver Bullied, CME*

However, using proper English, "one in a hundred years" cannot possibly mean, "a one percent chance in any given year." The two expressions are mutually contradictory. Once in approximately 36,500 days is blindingly obviously considerably less than the one percent definition you quoted. I do not dispute the Bureau of Meteorology's expertise, but I do not understand the reluctance of people/firms/ writers/ Departments to use clear, concise,

ZH836301
*Chief Commissioner*

If you understood statistics, you would realise it is impossible to express figures in the way you desire - I'm not having a go or expecting that you should, as it's university level stuff, but there is a reason things aren't as simple as you would naively expect.

One in 100 years is an expectation value - the average number of events expected over a 100 year period will be one. The expectation value is simple for discrete events like flipping a coin, for example, the expectation value for heads of 100 flips is 50. However, to deduce such things for continuous events you need to use calculus, and it gets messy.

In this case the probability for a one in T year event occurring once (or importantly, more) over n years is:

P = 1 - (1-1/T)^n

Ie. over 100 years the probability it occurs once or more is 63.40%, and thus for it not occurring 36.6%. Over one year the probability of at least one event is 1%, with a 99% chance it doesn't occur. The messiness comes from the need to consider infinitesimal time (ie. the probability of the event occurring over a infinitely small time frame) which allows for the possibility of more than one event in a given year. There is also a static assumption, which explains why 1:100 year events tend to be clustered.

Consider simply a 1:5 yr event, ignoring for simplicity the possibility of more than one event a year (ie. simply stating that the event either does or does not occur in a given year):

The probability of it occurring in a year is 1/5, and not 4/5, then the probability of N events in five years is:

Pr(N) = A(N) x (4/5)^(5-N) x (1/5)^N where N is the number of possibilities of the order of the event occuring, ie.

For 5 years, there are 2^5=32 possibilities of how the events are ordered

N=0: Pr=1x[(4/5)^(5)][(1/5)^0]=32.769%

N=1: Pr=5x[(4/5)^(4)][(1/5)^1]=40.96%

N=2: Pr=10x[(4/5)^(3)][(1/5)^2]=20.48%

N=3: Pr=10x[(4/5)^(2)][(1/5)^3]=5.12%

N=4: Pr=5x[(4/5)^(1)][(1/5)^4]=0.64%

N=5: Pr=1x[(4/5)^(0)][(1/5)^5]=0.032%

The expected number of events is the probability of that number of events by that number of events:

Ie. Expected value = ~0.33*0+0.41*1+0.20*2+0.051*3+0.0064*4+0.00032*5 = 1

Note that 2 events has a probability of 20%, and three of 5%, so not completely unexpected. For completion we really need to consider multiple events in a year which will change the probabilities slightly (since we have possibilities of N=6,7,8...) but isn't really necessary for low probability events, and won't change the expected value.

However, using proper English, "one in a hundred years" cannot possibly mean, "a one percent chance in any given year." The two expressions are mutually contradictory.

As you can see, a probability of 1% in a year gives an expected 1 event in 100 years - they mean the same thing.

justapassenger
*Minister for Railways*

However, using proper English, "one in a hundred years" cannot possibly mean, "a one percent chance in any given year." The two expressions are mutually contradictory. Once in approximately 36,500 days is blindingly obviously considerably less than the one percent definition you quoted. I do not dispute the Bureau of Meteorology's expertise, but I do not understand the reluctance of people/firms/ writers/ Departments to use clear, concise,accurateEnglish.

Valvegear
*Oliver Bullied, CME*

And, for the benefit of the condescending

My comments about correct English stand. The purpose of language is to communicate, and the expression under discussion obviously fails to do this with a large number of the public whom it is meant to inform. This "large number" includes people who did "university level stuff".

And,

ZH836301
*Chief Commissioner*

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