Endlich hat sich mal jemand Gedanken gemacht.
It comes from a bunch of textures which were posted here a few days ago. As well as reducing these textures to four bits, I made some improvements. No longer does dirt and sand go right up to the white line at the edges of the track, nor does grass any longer grow perfectly in a line against the road or a dirt area. Instead, you see the ragged edge of the asphalt just beyond the line, THEN the dirt, sand or grass (and in the case of dirt, a ragged edge for the grass on the outside). Similarly the grass above the curbs no longer grows perfectly straight, but has some blades falling on top of the curbs themselves, for a more natural appearance. The grass outside of where dirt is at the edge of the race track now has the appearance of dirt having been thrown onto it. Sand is sandier. Also, I added two new textures, improving the look of the start/finish line and the grid markers (previously they were done all in a solid colour; now they use a full palette of 15 colours -- plus one for transparency -- to look more natural). Unfortunately, the white lines around the race track are done in the track's 3DO as untextured polygons, so they must remain solid white unless you want to edit the 3DO!
For Watkins Glen:
These came from Berca's kit. The asphalt has been made brighter and smoother. The hay now is coloured like hay. There was some editing of edge textures to reduce obvious "loops". I have replaced Berca's modern-style Armco with Matt Knutsen's historically accurate Armco (see pictures of the 1967 USGP and look at the Armco -- notice how the struts protrude above the metal barrier). I also added new textures for the long white lines (and improved the dotted white lines), the grid boxes and the side road, and applied a Kendall ad on the haybales at Turn 1.
The trick to making four-bit textures from the 16-bit ones is to do more than have PSP reduce the colour depth to 16 colours. When you do that, the image takes on a dull, desaturated appearance. So you must resaturate the colours on the textures, and in many cases increase or reduce contrast before or after reducing the colour depth. Any textures which contain bits of road (edge or dotted line textures) must have careful attention paid to them, to make sure that the colours used for the piece of road are actual colours used in the road's main texture. Otherwise, textures like the dotted line will appear obviously as a long line texture with white bits, rather than looking like it's actually a series of short lines placed on the road. It's far more difficult to make that look right with a 16-colour palette than it is with a 16-million-colour palette!