k ~J1kLdR 1I- V X1117 NX X %-I PI "Xk,3x L.JPX X TECHNICAL FIELD This invention relates to devices which may be placed in between tram tracks above or below the ground for displaying information to waiting tram passengers. BACKGROUND In the operation of tram services, tram stops and shelters are a necessity to tram users for the smooth running of the tram services. Due to trams generally arriving at regular intervals of a few minutes, advertising companies have a small window frame of time to grab the attention of the tram user to advertise a product. Advertising companies have realised this potential time and have made advertising more attractive by locating light boxes to highlight their advertisings. All of the current points of advertising at tram stops rely on the target customers viewing the advertisements in the vertical plane, which requires a special vertical mounting. This current vertical mounting is normally displayed behind the targeted tram user. At most tram stops the users occupy the space at the edge of the tram stop and consequently do not face the traditional advertising hoard behind them, instead facing the tram track in front. It's not very often you will ever see seats set-up at tram stops, facing away from the tram tracks. Bearing this in mind, the main focus of people's vision is usually vertically downwards i.e between the tram tracks themselves. Subsequently this makes the perfect placement to grab the attention of the tram user to advertise a product. [t's well known that to grab someone's attention is one thing, to keep it is another. Advertising between the Lram tracks opens a new ball game in the advertising field of tram stops. To start with a single advertising between tram tracks is a start to getting tram users attention, but to advance and keeping it from here needs to be a way of having multiple advertising displayed. SUMMARY OF THE INVENTION In one aspect, the present invention provides an information display system including a display means and securing means for fastening the display means between a pair of rails for a tram, wherein the display means displays different information at different times. The different information may be displayed electronically, in which case still images or video, for example, may be displayed. The display means may include a rotating belt having two or more printed images attached thereto. For example, the rotating belt may have a number of different posters displaying several different advertisements attached to it. In one particularly preferred embodiment, the display means includes at least one flat panel display. The flat panel display is preferably an LCD screen, but may be any suitable substantially planar display device. In one embodiment, the display means includes two or more flat panel displays, and the information displayed on one of the flat panel displays at time t depends on the information displayed on at least one of the remaining flat panel displays at time t. This allows for advertising to be linked to run over not just one screen but many screens, this giving a more dynamic effect to draw the tram user's attention. The display means may be installed in a cavity between the rails to allow the device to be kept flush with the surface between the rails, thus reducing or substantially eliminating the risk of theft of the display secured above the concrete. The option of advertising with a screen can keep the tram user occupied throughout their whole waiting time for the next tram giving a great selling point. Another advantage of advertising on a screen is 'aving something flashing draws the attention of the tram user. With the added bonus use of sound, this would make the optimum advertising technique to keep tram users attention, giving fantastic advertising >otential. These screens could not only be used to advertise but has potential to demonstrate other information i.e tram use, tram routes, new systems introduction etc. DESCRIPTION OF PREFERRED EMBODIMENTS Referring to Figures 1 and 2, there is shown a display means in the form of an LCD screen (6) fastened >etween a pair of tram tracks(3) using frame (4) and locking mechanism (2). The screen displays a still or noving image displaying information such as advertising. The screen may be installed between tram tracks 3) in a cavity (8) keeping the device substantially planar and flush to the tram tracks(3), displaying nformation visible to a person located to the side of the rails. Furthermore, the fastening within a cavity so is to keep the device flush with the surface reduces or substantially eliminating the risks of the device being stolen, this also substantially eliminating any tripping hazards associated with the device. The LCD screen (6) may display varied advertising or other information including still images and .ull movies, optionally including sound. The display means may extend along the tram tracks (3). For example, it may include one large LCD screen, or many interlinked screens, thus allowing a large amount of information to be displayed. To protect the LCD screen (6) from damage, a sheet of polycarbonate (5) or alike may be placed on op and secured to the concrete (11) greatly reducing or stopping any impact and damage to the LCD screen '6). To secure the polycarbonate(5) or alike to the concrete(1 1), a locking mechanism(2) will be used that .equires key(1) access, this will greatly reduce theft and give easy access to the engineers for future naintenance. The LCD(6) screen(s) can be secured on top of the surface or placed in a cavity (8) keeping the ,creen planar to the tram tracks(3). Powering(7) the LCD(6) screens can come from a number of sources ie. battery, mains and/or solar power. To display many images and movies, a storage medium such as a hard-drive(18) may be installed to ;tore information, images and movies to display onto the LCD(6) screens. The storage medium(l 8) may be nstalled in or in close proximity to the LCD screen (6), or alternatively in a separate location. If the storage -nedium (18) is installed in close proximity to the information display device, it may be kept in a separate locked storage compartment. Communication between the storage medium(18) and the LCD(6) screens can be achieved using either cabling or a wireless connection. In an alternative embodiment, shown in Figure 3, there is provided a system(12) which will have a rotating belt(1 5) mechanism. This mechanism(12) rotates a belt(1 5) which has a number of different posters(14) secured to it, thus displaying several advertising displaying to a person located(20) to one side of a pair of tram tracks(3). The rotation of the belt(1 5) will be determined by a timer(19), each poster(14) will be displayed for a pre-selected time until the mechanism rotates by means of a motor(16), displaying a different advertisement(14) to the surface. Preferably the device will be installed into a cavity (8) between the tram(3) tracks keeping the device planar and flush to the tram(3) tracks, a source of powering(7) the device to rotate the belt(1 5) will be powered(7) by battery, mains power, and/or solar panels or alike. Inside the rotating device(12) a lighting system(1 3) may be installed to illuminate the poster exposed to the surface. These lights(13) may be switched on by means of a timer(1 9) or light detector(19) to reduce electricity(7) cost and saving bulb life(1 3). The rollers(21) and belt(1 5) configuration of the device need not be limited to only two rollers(2 1); many rollers can be used giving an increased belt(1 5) length, this increasing the number of advertisings(14) available to display. 2 Diagrams Number Index 1. Key 2. Locking bolt mechanism 3. Tram tracks 4. Frame 5. Protective layer (ie. Polycarbonate) 6. LCD screen 7. Power supply (ie. Mains, battery or solar) 8. Footings 9. Bolt footings 10. Power cable 11. Concrete between tram tracks 12. Rotating display device 13. Lighting - Illuminating advertisings 14. Posters (shown in red, green, blue & purple) 15. Rotating belt with posters attached 16. Motor - driving belt 17. Sequence direction 18. Hard-drive 19. Timer/Light sensor 20. Side of tram stop 21. Belt roller(s) 22. LCD bolts 4