In the passenger calibration thread, I wrote that we need to be working to a figure of about 1,250 potential passenger trips per head of population per year, constrained by journey time tolerances.
Turning to some actual data about mail, in 1992, there were about 54,000,000 letters posted a day according to "A History of Britain's Post" by Nance Fyson (ISBN 0-946003-99-8).
Google tells us that the UK population was about 57.5 million at the time. That gives an average of 0.93 letters per person per day or 343.02 letters per person per year.
The current weight of a mail bag in the code is 50kg, but that is obviously far too big (the size of a small person), as mail bags were often easily carried by hand. This needs to be reduced by more than fourfold: according to
this website of the people who make the current mail bags for the Royal Mail, their limit is 11kg. On the basis of that weight, about 550 first class letters per bag could be carried (based on the maximum permissible weight for a first class letter).
If we divide 343.02 by 550, we get 0.62, meaning that each head of population should generate 0.62 bags of mail at 11kg per year. If we assume a waking day of 16 hours (as we are doing for the passenger generation, different to the 13 hour day suggested above), each head of population would generate 0.000106164 bags of mail per game hour. A small town of 2,000 would generate 0.212328767 bags of mail per game hour (or take five game hours, nearly a game month at 250m/tile and 21 bits per month or 125m/tile and 22 bits per month) to generate one bag of mail. On another view, it would require a passenger to mail ratio of 2,016:1 if we assume 1,250 potential passenger trips per head of population per year.
On that basis, a town such as
Slough with a population of around 140,000 would produce 14.86 bags of mail per game hour. This suggests a need rather to increase the size of towns, largely by increasing the level of larger buildings - this is in any case something that has been identified as necessary for passenger generation.
Currently, the mail carrying vehicles in the game are calibrated on the same basis as passenger carrying vehicles, especially as to their capacity. Unfortunately, finding real capacity data for mail carrying vehicles is not easy: the foremost Google search results for 'capacity "bags of mail"' are web pages about Transport Tycoon vehicles. There are some pages that give the mail capacities of sunken ocean liners, such as the
RMS Empress of Ireland, which was carrying 318 bags of mail at the time of its sinking in 1914, or the Titanic, which according to
this website, had 3,364 bags of mail and between 700 and 800 parcels when lost on her maiden voyage in 1912.
This source suggests that the capsules of the London Pneumatic Dispatch Company could carry 35 bags of mail each. Sadly, these are unusual vehicles and it is not clear how these compare in size to ordinary mail vehicles, except that it is clear from the article that their capacity was higher than that of carts.
More useful information appears
here about the Postal Special, the train that featured in the famous 1936 documentary the "Night Mail" (and the poem of the same name). There, it states that the whole train carried about 3,000 bags of mail. Page 276 of the same text records that each "R. P. O. car" would contain between 250-280 bags (suggesting that the train was up to 12 carriages long). Page 275 records that this was the largest of all special mail trains, running from London to West Scotland at nigh, although dropping off and collecting mail at many destinations and transfer stations along the way.
I wonder whether the modern size of 11kg per bag might even be too much for our bags. Older pictures seem to show smaller bags, not filled as much as the modern bags are when at their top filling line. It might be quite rare for postal bags to reach their maximum capacity. Even if we assume half that, at 5.5Kg/bag, that still gives us, however, only a very small amount of mail generation.
Thoughts on this situation would be much appreciated.
Edit: A somewhat unusual piece of research on mail bag weights: according to
this somewhat angry forum thread, "Mr. Grumpy", who is apparently a postal worker, after his tirade against the original poster, states that he delivers 12 bags per day averaging 130Kg, or 10.83Kg/bag.
According to
a plaque in an American city, a large seed company was receiving about 100 bags of mail per day in 1917.
According to
this source about the now defunct underground narrow gauge mail only railway in London:
Jane Rendell: The Post Office railway runs under here. It was started in 1913, but halted by the First World
War, the tunnels were only completed by 1926, and opened in 1927. Thirty four new trains were added in
1981. The railway is six miles long and runs from Paddington to Whitechapel, with six sorting offices, plus
the main sorting office at Mount Pleasance. The trains are 27 foot long and consist of 4 containers, each
carrying 15 bags of letters in 6 bag panels. Trains run in each direction every four minutes at peak times,
moving 50,000 bags of mail per day. The GPO Headquarters is under the King Edward Building, where there
is a maze of tunnels in a figure of eight shape. These include two twin blind tunnels under Angel Street. Here
the shaft connections to the deep level post office tunnels stop abruptly. There were to be extensions to the
south east to Elephant & Castle/Waterloo and to Victoria.
