The American Truck Simulator 1.40 patch includes a new lighting system, an extended chassis update, a Western Star 49X update, New Mexico & Oregon DLC Viewpoints, and more.
For the new lighting system, changes had to be made to the graphic renderer, its code, and existing in-game world objects such as in-game assets, textures, and materials to better work "with the new physical model of the new light system." This is the biggest graphical update to the game in years, and it gives the game a fresh new look for the game. If you would like to know more about the nitty-gritty of the new system, you should check out the blog post here.
Interestingly, this new lighting system isn't completely finished and there will be more changes and improvements to be done in the future. Basically, while the open beta for this lightning system is complete, the American Truck Simulator team would like feedback and opinions on the new graphics update for both this game and other games in their library (namely, Euro Truck Simulator 2 one imagines.
The Extended Chassis update brings players long and short chassis types to customize your truck. The update includes 4x2, 8x4, and 8x6 chassis types that can be used for a bunch of different trailers. If you don't know your trucking lingo, the 4x2 chassis is a type of single-axle truck that is frequently used for local distribution deliveries and for hauling doubles. The 8x4 and 8x6 chassis are the big boy trucks that can do heavy hauls and are used for pretty much every heavy load.
The Western Star 49X has received 2 additional sleeper cabin options and 36 chassis variants, which are comprised of different lengths and fuel tank options on 6x2, 6x4, 8x4, and 8x6 axle configurations. There are also 5 lengths for both the Set-Back and Set-Forward axle configurations, so you can use this truck for pretty much everything you want.
The new viewpoints for New Mexico and Oregon have been added, which are certain spots across the map where players can activate an in-game cutscene to show off a near location or place of interest. These can be found on your GPS as a gray question mark, so be sure to check them out when you drive by them.
For the full announcement, be sure to check out the Steam blog post here.