-44. Sorry. Couldn't resist.
If my memory serves me correctly...
With HS20, you have a 20 ton vehicle with 4 tons on the front axle, and 16 tons on the rear dual or single axle combination. I would have to look at the sketch to see the distance between axles.
With the HS20-44, you have a 44 foot overall length, 14 foot tractor and a 30 foot trailer, with 4 tons on the front axle and 8 tons on the rear of the tractor at the hitch, and 8 tons on the rear axle. There are tweeks to this arrangement too.
You can verify this either with AASHTO or the 1963 California Highway Design Manual. I know - dating myself here.
Mike McCann
MMC Engineering