In my work properly to implement the passenger and mail classes feature in the pakset in respect of rail vehicles (this work is complete for all other sorts of vehicle), I have been spending some time improving the provision in the pakset in respect of very early railways (pre-1850s), which has been very limited and not very accurate. Those subscribed to the Facebook group might might already have seen some of the work, but I thought that it would be sensible to post it in the forum, too, as not everybody uses the Facebook group.
The work is not yet complete, but here is a brief overview of some of the changes.
Firstly, here is a stagecoach on rails, of the sort used by the Stockton & Darlington Railway from 1826 onwards:

To accompany this, there are now rail versions of the three main breeds of coach horses and a rail version of the staging post, as this early railway stage coach did not use railway stations, but rather set down and picked up passengers in the same manner as a stagecoach.
Note that this stagecoach can be pulled at a good speed by a single horse, just as it was in reality. This is owing to the much lower rolling resistance of rails compared to roadway.
Here is a train of Liverpool & Manchester Railway carriages behind Stephenson's "Rocket":

The locomotive (in common with all of the early locomotives) and carriages have been re-rendered to take advantage of the new transparent workflow that greatly improves the appearance of these smaller vehicles with fine details. The carriages have been re-scaled to the correct size (they were previously too large), and the liveries have been made of a more realistic set of colours. There is now the option for a covered second class carriage (the Liverpool & Manchester Railway initially only carried first and second class passengers, the second class being in open wagons). The mail carriage now carries passengers (as it did in reality) at a lower density, and higher comfort/class than the first class carriages (these are set to "very high" by default), with the mail being carried in a separate mail locker, which works in the same way as the holds on the ships.
There are now early and late forms of these carriages, the early forms having the short wheelbase and dumb buffers that these carriages had when new, the later form having the longer wheelbase and sprung buffers that these carriages had later, which made them more stable at high speeds and more comfortable for passengers. The early forms can be upgraded to the later forms at a cost.
Here is a train of Leicester & Swannington Railway carriages of 1832/3, hauled by a new Stephenson Goods 0-4-2 locomotive of a type used on that line:

These are a cheaper, lighter, slower alternative to the main line carriages used on the Liverpool & Manchester Railway, and may be more suited to local lines than the LMR vehicles.
Another one of the new engines to fill the large gap that had formerly existed in the late 1810s/early 1820s is this, Stephenson's Improved Engine of 1816, as used in the Killingworth collieries:

A number of other early engines have been added, including Stephenson and Dodd's Patent Engine of 1815, Hackworth's Sanspariel of 1829, the "Lancashire Witch" of 1828, the "Royal George" of 1827 and the "Vulcan" of 1834.
The waggonways have also had entirely new graphics, with a distinction now being drawn between the original purely wooden waggonways:

and the later waggonways topped with cast iron plates:

Note the earlier style of makeshift buffers.
The wooden waggonways are much cheaper to construct, but wear out much more quickly than those topped with cast iron plates, introduced in 1767. The maximum weight allowable on these waggonways has been increased considerably to allow early steam locomotives to use them, but using steam locomotives on these waggonways will wear them out quickly - on the wooden waggonway, very quickly indeed.
Note also the re-scaled chauldron wagons re-rendered using the new transparent workflow.