System

Basic Operation

The passenger uses the system by going to the nearest station on the network. Stations are distributed around the area served like bus stops or cab ranks. At each station there are a series of berths at each of which the passenger can select their desired destination. This is done via a smart card process. Because each passenger can be identified by their smart card the service can be personalised to respond to any special requirements of the passenger. The passenger destination selection is passed to central control which provides movement instructions to the vehicle assigned to the berth.

The passenger boards the programmed vehicle which takes them to their desired destination automatically, non-stop and by the best available route. At the destination the passenger leaves the vehicle, which may either wait there for the next fare or, alternatively, be redirected by central control to places with known demand.

Central Control

The central control system responds to the passenger’s request by allocating a vehicle for the journey and instructing the vehicle on the required path and timing for that journey. Each path is unique ensuring there is no interaction between vehicles. This provides the first level of active safety in the system. The central control system also controls the empty vehicle management process which ensures that vehicles are sent to where they are needed.

The central control function has been the subject of extensive simulations by ATS since the start of the project and the functionality has been well developed and tested. Simulation results show that average waiting times will typically be under 15 seconds and the 95% of passengers will be served within a minute.

The simulation uses a "synchronous" control system which allocates vehicles to slots in the same way as an aircraft control process. Some further comments on this are provided in the comparison section (LINK).

Vehicle Control

The vehicles are controlled autonomously. Once the vehicle has received its instructions form central control it will continue to its destination without any need for further central control input. Extensive tests have been done of various forms of vehicle control. ATS has performed full scale system evaluations tests on the various test sites to examine control methods based on wire guidance, optical and radar sensing, embedded track magnets and local sensors based on ultrasonics or lasers. The last two of these approaches were found to be significantly more reliable and robust. A combination of these approaches will be used in the final system.

Automatic Vehicle Protection System

The ultimate protection on the ULTra system is provided by an independent Automatic vehicle Protection (AVP) system. This is based on a fixed block signalling system parallel to that used on railways. The fixed blocks are defined by inductive loops set into the track which interact with sensing circuits on the vehicle.

Regulatory Approvals

The overall approach to automatic vehicle control has been approved by HM Rail Inspectorate, who have provided their consent to the carriage of passengers on the prototype system. This followed on a full hazard analysis and failure modes and effect analysis undertaken in conjunction with industry safety specialists. The documentation resulting from these analyses provided the basis for the HMRI evaluation and consent. HMRI have also provided consent in principle to the approaches to be used in the initial Heathrow scheme which includes operation in tunnels.