Please see the VGG entry for the original Transport Tycoon for more details.
Transport Tycoon Deluxe
Two Transport Tycoon games were released, dubbed Transport Tycoon and Transport Tycoon Deluxe. The deluxe version, as its name implies, is an expanded and improved version of the original game. (A "World Editor" expansion pack was also released for the original Transport Tycoon, but was overshadowed by the Deluxe version released shortly afterward; interestingly, it featured an alternate, Martian set of graphics, which did not appear in TTD).
The primary difference between the games is how signals operate. The original Transport Tycoon allows only bi-directional signals, which allow trains to pass in either direction. The deluxe version introduced uni-directional signals, that only allow a train to pass in a single direction.
The change in gameplay from this relatively minor alteration to signals is significant, as the old bi-directional signals would allow a train to travel in both directions. This is similar in concept to having a single lane street that would allow traffic from either end. Unsurprisingly, it was possible for two trains to try to travel in opposing directions towards each other on the same run of track. While this would not result in crashes on a properly signaled route, it required either the building of extra track to allow the trains to pass each other, or the building of a great many tracks in parallel to avoid the problem in the first place.
The new uni-directional signals allowed one-way tracks to be built, which gives the player much greater control over how the railway network could be run. This allowed for efficient routes to be built, and prevented trains from trying to travel the "wrong way" down a section of track. By incorporating both uni-directional and bi-directional signals, effective switching yards, junctions, and other useful designs could be built. It also unlocked the ability to build continental-length railroad systems by incorporating one-way rails in both directions and the ability to merge other rails with the main one. This is a highly used strategy because it allows for intercontinental transport of goods which results in high return rates for the user.
The deluxe version also expanded the game to provide tropical, Arctic, and toy-town environments, as well as the classic temperate environment. The new environments came with different industries and challenges. For example, towns in the Arctic environment would not grow without regular deliveries of food, and those in the tropical environment also need access to fresh water.
Due to copyright issues with using names of real vehicles in the original Transport Tycoon, the default names were replaced with fictional ones in Transport Tycoon Deluxe. Players however are allowed to rename their vehicles and stations as they please, which can be useful for identifying individual services in a network. Players are also able to rename towns, which provides for a more personalized game play.