Sustainable Transit Technology
Minitram GRT Systems
Minitrams are state-of-the-art, light urban transit vehicles (sometimes known as Group Rapid Transit) designed to operate in town/city centres, visitor attractions, airports, exhibition sites and park-and-ride applications.
The Minitram technology seeks to offer the system characteristics normally associated with conventional rail-based tram networks through the flexibility and cost effectiveness of automotive and commercial vehicle technology, combined with a concealed (below ground) wire guidance technology called 'Safeguide'.
Safeguide ensures accurate navigation along narrow transit corridors - just like invisible rails - and precise docking at stops/platforms and stations. This is especially relevant in historic town centres, where conventional bus lanes or tram lines would be impractical. Using this system, the vehicles can be driven in fully automatic mode (on segregated alignments only), semi- automatically or even manually with a driver where no guideway exists.
Minitram GRT systems are significantly cheaper than a conventional tram or light rapid transit system and do not require intrusive infrastructure such as overhead wires or electrified rails. The vehicles are small scale and can travel along roadways with shared occupancy, dedicated alignments, through pedestrian areas and even indoors within shopping centres or other building complexes.
Running every few minutes, a fleet of Minitrams can provide a continuous orbital service around any congested town or city centre. By virtue of Safeguide, they are able to navigate precisely within dedicated transit lanes on an existing highway or else along dedicated, paved alignments and in pedestrian areas. The core service can also connect with a network of radial or cross-town routes serving schools, housing estates, business centres, the local railway station, various park and ride sites and other important amenities. As they are non-polluting, small scale and accurately steered, they can also run though pedestrian priority areas as well as indoors - for example in shopping centres.
The modular design of the Minitram is such that cars can be manufactured in a range of sizes (in terms of length, width and interior seating arrangement) to suit the local operating environment and capacity requirements.
Each Minitram is individually powered by a high performance AC traction motor coupled to a software controlled, three phase inverter control unit. It is powered by multi-string lithium battery modules. These are capable of operating in extremes of temperature from -50°C to 75°C and delivering very high energy output from a comparatively lightweight battery pack. Depending on the type of lithium technlogy used, the batteries are also capable of high charge rates through a suitable fast-charge infrastructure to provide extended daily duty cycles. In comparison with a standard lead acid traction battery, the lithium cells have approximately four times the life expectancy (and cost about the same over a 20 year life cycle) and provide a superior stored energy to weight ratio.
Although the Safeguide system automatically steers the vehicle, in all other respects - including braking and accelerating - the driver remains fully in control. Based around the concept of detecting low frequency signals generated through underground cables, the breakthrough with Safeguide is its unique, high integrity watchdog steering system. This patented device is designed automatically to take over from the primary system should an emergency condition be detected. Such an approach differs significantly from previous forms of electronic guidance, which have relied on the driver to take evasive action in the event of failure.
To ensure the highest possible level of safety integrity, TDI has designed Safeguide against very specific performance criteria identified in a safety case strategy. This strategy has been developed through painstaking consultation with industry experts and Her Majesty's Railway Inspectorate (HMRI).
In terms of infrastructure, Safeguide is extremely cost effective. A pair of signal cables is buried down the centre of the guideway approximately 75mm below the paved surface and 400mm apart. Signal generators and transponders are located at stations/stops.
Aside from the obvious benefits of a fixed infrastructure transit system, the four-wheel steered Minitram, under Safeguide control, can improve on the performance of conventionally guided vehicles by achieving a virtually gapless, level boarding solution. This is of particular interest to operators and local authorities in meeting their obligations of stringent access requirements under DDA legislation.
Safeguide offers significant advantages over other forms of guidance such as O-Bahn (kerb guidance). The infrastructure is completely invisible; it is inexpensive to install (a complete Minitram system inclusive of vehicles and infrastructure is estimated to cost around £1m per km); it will work in all weather conditions and there are no trip hazards for pedestrians.
At the invitation of Earl Spencer, a prototype, rubber tyred Minitram was demonstrated during the summer of 2002 at Althorp House (last resting place of Diana, Princess of Wales). During the seven day week, three month season, the Minitram carried around 70,000 passengers - including many wheelchair users.
Stratford upon Avon
The first urban application for Minitram was in Stratford upon Avon, 2003, where a three month trial (funded by Warwickshire County Council, Stratford on Avon District Council, the West Midlands Regional Assembly and the Royal Shakespeare Company) was conducted successfully around the town centre. During the trial 1400 people used the Minitram with a 98% positive response rate. In conclusion, both the District and County Councillors supported the view that the Minitram as a new form of public transport would have a future in Stratford. The project went on to form part of the "World Class Stratford" initiative.
In November 2005, Bradford City Council, in conjunction with First Group operated a six-week trial of the Minitram. The service ran across the city centre, along pedestrianised shopping streets, connecting the city's two railway stations. Plans are now being developed to install a permanent system, incorporating electronic guidance on the off-street sections of the route.
TDI are working on the next generation Minitrams which will feature the ability to close-couple and articulate a number of modular elements to form higher capacity vehicles.