LEGO Train History

The history of Lego trains can be divided in four distinct eras.

The blue era (1966-1979)

The blue era is named after the colour of the rails.
1969 saw the introduction of Lego trains with Lego set number 080. The first train sets were push trains. Set number 115 introduced 4.5V battery operated trains (a railcar carried the batteries to supply power to a motor in the locomotive), which are probably the most compatible to tracks of all LEGO trains, and train sets numbered 720 (1969) and up operated on 12 Volt electrified rails.

The gray era (1980-1990)

In 1980 the trains theme got a major overhaul. The color of the tracks changed to grey (hence the name) and the transformer changed to support utility functions as remotely-controlled points, signals, wagon de-couplers and crossings. Not just the tracks changed color - the models themselves changed to a much more realistic appearance. Models were offered with much longer carriage/wagon bodies (although still considerably short of true scale length), proper swivel bogies and special windows which simulated having a pull-down glass section.
The 1980 train catalog enticed Lego fans with nighttime dioramas featuring lampposts and lights inside the trains. Notable train sets include the Electric Intercity (7740) and Steam Locomotive (7750) (for its large wheels). Many old 12V models (such as 7740) are now highly-prized additions to some 9V layouts as a change of motor is all that is required for compatibility.
Trains and tracks of the blue era after power was added to the tracks are compatible with the gray era. Additionally, those blue era trains with internal batteries that do not take power from the tracks are compatible with all tracks.
Blue and gray era trains were never officially introduced to the United States - the first train sets to go on sale were 9V models.

The 9V era (1991-2007)

1991 saw again a major overhaul in the train line. Tracks gained a new realistic appearance with (9V) power coming directly from the rails - in the blue and grey era electric trains were powered by an extra electrified (12V) piece of track between the rails. The new line abandoned the 12V power in favor of the 9 volt system to make it compatible to the battery operated elements found in the Lego Light and Sound line of sets. The remote-controlled accessories from the 12V system were also abandoned, with only manual point control available and no signaling capabilities. This effectively reduced the maximum practical size of the layout as well as the complexity of train operations that could be supported. This product re-design was formulated by The LEGO Company thinking at the time, which promoted simplification in all product lines, but drew criticism for reducing the "playability" of LEGO toys.

The 12V locomotives were not compatible due to the change in voltage and means of powering the motor, but many can be retro-fitted with 9V motors. The gauge did not change, therefore older rolling stock could still be used. However, the rails and wheels now have a different profile, and some users have found that 4.5V/12V wheels may have trouble passing through 9V switches.

Currently, 9V train sets are available through the LEGO Shop at Home ordering service and to some degree through LEGO Brand Retail stores. Custom sets can also be designed and ordered online using the LEGO Factory system. The 9V train line will be replaced, along with the RC train line, by a new type which uses LEGOs Power Functions systems for operation.

The RC LEGO Train Era (2006-2009)

In 2006, Lego introduced a new line of remote control trains. In an effort to reduce the cost of the track and make it easier for newcomers to enter the Lego Train community, Lego started making track entirely made out of plastic (foregoing the metal rails), and introduced a new train motor that runs on batteries and is remotely controlled via infrared (IR) remote control. This move has proven to be controversial in the Lego Train community, as the system has proven to be unfavoured by the community.

As of March 2007, LEGO only sells 9V train hardware through its Shop at Home ordering service and to some degree through LEGO brand retail stores. The 9V line is now referred to as the LEGO "Hobby Train" and is aimed at advanced, older train builders. LEGO offers few 9V train models at this point but compensates via the LEGO Factory system. Through this system, builders around the world design their own train models using LEGO Digital Designer, a computer program distributed freely by LEGO. These models can then be ordered from LEGO or shared online. Through this system, hundreds of new LEGO train models designed by fans are available.

LEGO also released set 10183 Hobby Train Box in March 2007. This set, designed by ten well-known LEGO train fans, includes over 1000 elements that can be used to build a variety of models. This set, in conjunction with LEGO Factory, represent the future of the LEGO Hobby Train.

The RC Train System versus the 9V Trains System

The introduction of the RC train line has some benefits, notably:

-Less expensive track, as track sections do not have have metal strips on the rails.
-The decreased production costs have already resulted in a new track piece being added to the system for 2007 (the double flying cross-over).
-Remote control allows for the independent control of multiple trains simultaneously. The 9V system allowed the speed of the train(s) to be controlled only by varying the voltage of the track, so any trains on the track would be controlled at the same time. The first released sets (2006) have 3 different InfraRed (IR) channels available allowing 3 three trains to be run at different speeds and in different directions.
-Remote control also allows for one train to be controlled by multiple controllers—-useful for a user at each end of a line, particularly when the line ends are out of IR range of each other.
-More complicated track layouts can be created without having to worry about the electrical polarity of the rails (both the 12V system and 9V system have this problem because one center conductor (12V) or rail (9V) was meant for the positive terminal and the other rail for the negative terminal).

However, the RC system also introduces some new issues:

-Infrared is not an ideal remote control system, as fluorescent lights and physical objects may interfere with it. The range is inferior to radio control.
-The trains use regular 1.5V AA-cell batteries, instead of using a more powerful rechargeable system. Previous generations of (12V and 9V) LEGO trains were plugged into the wall, avoiding battery-charging issues completely. The remote control uses 3 AAs and the train power unit uses 6, for a total of 9 AA batteries in use at any given time.
-Initial anecdotal reports have raised concerns about the power output of RC motors, since they are now battery based, rather than picking up an almost infinite source of current from the tracks, as with the 9V system.
-The RC Engine is weaker than the previous 9 volt motor due to limited number of rolling stock recommended to pull as well as having trouble going up custom made slopes.

The "Power Functions" LEGO Train Era (2009-)

On October 1st, 2007, LEGO announced that they are discontinuing both the 9V and the RC train formats in favour of the Power Functions system, recently introduced in other themes such as Creator and Technic. The new system will retain the standard L-Gauge and will be as backwards-compatible as possible; basic dimensions will remain the same and rails will be interconnectable with both the 9V and RC rail systems, and therefore also with 4.5V era track. The system will be introduced in 2009, replacing the current trains.