I think the 45% will be found to be a 45% increase on the average haulage capacity of the existing fleet over the ruling grade on the system which is northbound through the ryhndaston tunnel.
On the information available to me I have calculated the weighted average capacity of the existing regular mainline fleet (not Y's and ZB's) to be 467 tonnes over this section. 45% increase results 677 tonnes per loco which roughly concurs with the 700 tonnes through the tunnel per loco target I have heard mentioned previously. My information may not be up to date or the mix of the fleet slightly different when the calculation was made which may account for the difference.
I think that is close to the figures I have read.
For those who are interested, once again from the 1978 Working Time Table engine loads on the Colebrook - Rhyndaston Section.
1 - X = 210 tonnes
2 - X = 410 tonnes
1 - Y = 360 tonnes
2 - Y = 610 tonnes
Bridgewater - Parrattah Section.
Auto Coupled Trains
1 - Z / ZA=670 tonnes
2 - Z / ZA=1320 tonnes.
Steam loads from the 1957 Working Time Table on the Colebrook - Rhyndaston Section
1 - C = 110 tons.
1 - CC, CCS, M or T = 150 tons.
1 - E = 160 tons.
1 - G = 250 tons.
1 - H or Q = 210 tons.
1 - R = 170 tons. Loads for double headed steam was 90% of rated load of the two engines on all lines.