ULTra Personal Rapid Transit System

Operational Robustness

The ULTra PRT system is purposefully designed to be robust and adaptable to a variety of exceptional circumstances that could otherwise impact on service during real-world operation. In addition to the safety and security provided in all aspects of normal operations, ULTra is able to continue to operate in a number of more extreme scenarios, as described below.

Adverse Weather Conditions

ULTra is designed to cope with a variety of weather conditions, and can operate as normal in heavy rain, bright sunshine, and strong winds, as has been confirmed by the extensive testing program run by ULTra PRT.

The ULTra system can also cope during periods of snowfall; as soon as snow begun to collect on the guideway, measures would immediately come into effect to prevent it accumulating. A dedicated snow and ice removal vehicle will be deployed and make regular sweeps of the guideway to keep it free of snow. De-icing fluid will be deposited on the guideway to ensure any remaining snow will melt sufficiently to run off as water.

Additionally, in areas where snowfall is common an "open" guideway design further prevents its accumulation and aids dispersal

View of elevated ULTra grid-style guideway from below.

Snow and Ice Testing Program

A testing program was undertaken in Denver, Colorado during the winter of 2007. The objective of the work was to obtain a better understanding of the potential impacts of snow and ice on the operation of automated small vehicles (specifically the ULTra vehicles) running on an elevated guideway and to investigate the effectiveness of an open glass reinforced plastic (GRP) grating for mitigating these impacts. A ground-level test track was constructed and testing was conducted using simulated freezing rain and natural snow. In addition to general observations, friction measurements were made using a V-Box manufactured by Racelogic.

Most snowfalls (except for wet snow with large flakes and snow under blizzard conditions) resulted in much lower accumulations on the grid than on surrounding surfaces because the snow tended to fall through the grid openings. Under light snowfall (<25mm on the grid) an average deceleration of 7.5 m/s² was measured. Under heavy snowfall (>25mm on the grid) an average deceleration of 7.7 m/s² was measured. These results indicate that snow that does not pack down and is forced through the grid by vehicle passes should not be problematic.

Furthermore, these tests were carried out at ground level, and it is likely that an elevated GRP track will be even more successful in mitigating the effects of snowfall.

Guideway Blockage

The ULTra system is designed so that guideway blockages are prevented from occuring wherever possible, for example by the employment of extensive Health Usage Monitoring Systems (HUMS) on the vehicles which ensure vehicles are taken out of service for maintenance well before any problem can develop to the point of stopping the vehicle mid-journey. As ULTra is expected to operate to aircraft standards of reliability, the possibility of breakdown is kept to a minimum, and the design of ULTra eliminates most of the reasons that cause cars and other transport modes to fail during a journey.

Even with these preventative measures in place, guideway blockage is still a possibility, and so ULTra PRT has developed a comprehensive action plan to deal with such an occurrence:

Firstly, any guideway blockage will be detected early by the control room operators using the CCTV system; the CCTV system covers the whole guideway and is constantly monitored.
In case of blockage, operations in the area of the system affected would be temporarily halted whilst a technician is dispatched to remove the offending item.
Once the blockage is removed the passengers will be able to complete their journeys.
Passengers will be kept informed throughout the process by the control room staff.

Therefore in the extremely unlikely event that a vehicle does break down a service vehicle will go and retrieve it immediately. The vehicle also has emergency exits and with the vehicles being self-powered, when no vehicles are travelling on the guideway it is entirely safe to walk on

Mains Power Failure

In case of mains power failure the control room has a battery powered back up which allows all vehicles on journeys to complete them. With this in place, and because the vehicles are all individually battery powered, the system is not brought to an immediate halt by power failure.

The system will at this stage not allow any new journeys to be booked and the control room staff will arrange for alternative transport for passengers until power is restored.