Automation versus driver-operated vehiclesIntroduction IntroductionTraditionally, rail rapid transit systems have been operated manually with one or more crew members on-board each train responsible for driving the rail vehicle or train, operating doors at stations, obeying signals and maintaining safe rail operations in co-ordination with centrally located control staff responsible for overseeing system operations as a whole (scheduling, service alterations, emergency response, communications). Since the 1960s, rail systems have been employing various degrees of automation to improve capacity, safety and reliability while also seeking to control costs. For the purposes of this discussion:
The decision to implement driver-operated or automated train technology in Ottawa will need to be considered in conjunction with other technology issues, including:
Other questions which need to be answered include: How advanced a system does Ottawa need or want? Will the public embrace full automation the way they have in other cities? Can automated systems operate reliably in the extremes of Ottawa’s climate? Overview of AutomationAutomatic train operation, or ATO, can be superimposed on any form of continuous supervision-based Automatic Train Protection (ATP) and as a consequence, the introduction of ATO on urban transit railways was closely linked to the transition from wayside signalling technology to cab-signalling technology in the latter half of the last century. The initial ATO applications used fixed block, coded track circuit technology with “speed codes” to indicate the maximum enforced speed. ATO functionality can also be provided with fixed block “digitally encoded”, profile-based track circuit technology as well as Communications-Based Train Control (CBTC) technology which can support moving-block operations through continuous train-to-wayside and wayside-to-train data communications, and train location determination that is independent of track circuits. Reference should be made to the paper on Signalling Systems in order to gain an understanding of the interaction between signal control systems and automated train operations. London Underground’s Victoria Line, which entered service in 1968, is generally regarded as the first ATO metro line. The Victoria Line signalling is based on fixed-block technology and the train driver (in actuality the guard) closes the train doors and presses a pair of "start" buttons to depart a train from a station platform; his position was more attributed to the union pressures of non-acceptance of the ATO system at that time. If the way ahead is clear, the ATO system drives the train at a safe speed to the next station and stops there. The Victoria Line would therefore be classified as semi-automatic train operation (STO). The implementation of ATO on other lines in the London Underground network is currently underway. Similar STO systems appeared in the U.S.A in the late 1960’s with the PATCO (Port Authority Transit Corporation) Lindenwold line in Philadelphia in 1969, the San Francisco/Oakland BART system in 1972, the Washington Metro (WMATA) system in 1976, the Atlanta Metro (MARTA) system in 1979 and the Miami Metrorail in 1984, for example. The Hong Kong MTR system also adopted fixed-block STO technology when that system first entered service in 1979. In Canada, the Montreal Metro is an example of a system using semi-automatic train operations. The first example of STO operations using CBTC technology was the Scarborough RT line in Toronto, which entered service in 1985. Other examples of STO utilizing CBTC technology include San Francisco MUNI (1997), Ankara Metro (1997), Hong Kong KCRC West Rail (2003) and New York City Transit Canarsie Line (2006). An example of a driverless train operation, but with an onboard attendant would be the London Docklands system that entered service with CBTC technology in 1994. The first examples of unattended train operation on a metro line, with no person aboard (UTO), were in Kobe (Japan) in 1982, Lille (France) in 1983 and Vancouver (Canada) in 1985. The Kobe and Lille systems were based on fixed-block technology, whereas the Vancouver system utilized CBTC technology. Other examples of UTO utilizing CBTC technology would include, for example, Lyon Line D (1992), Paris Meteor Line (1998), Kuala Lumpur (1998) and Singapore North-East Line (2003). Examples of UTO based on fixed block technology would include Osaka (1982) and Copenhagen Metro (2002). The examples above are not intended to be an exhaustive list of all ATO systems world-wide, but rather to demonstrate the widespread application of ATO technology over the past 40 years, and to provide an indication of the maturity of this technology. System CharacteristicsTo assess the different modes of operation, we need to consider those characteristics which differentiate automatic from driver-operated trains. These are primarily:
CapacityThe first fully automated systems introduced tended to use relatively small vehicles compared to modern LRT or metro vehicles, as the desire was to implement cost-effective technologies in corridors, which could not justify the use of traditional subway/metro technology. Some of these systems (Vancouver, Lyon) have upgraded their original rolling stock to larger vehicles as demand has increased in the decades since these lines were opened. The distinction of vehicle size and mode of operation is disappearing as more systems adopt automated operation on existing and new lines and vehicle-type is no longer a barrier to implementation. ATO operation can allow closer headways between trains, which increases the carrying capacity of the line over that of a driver operated system, which must account for variances in individual operator behaviour and provide a larger safety margin between trains. The ability of automated systems to closely control vehicle performance results in a more reliable operation, which would allow per-train planned capacity to be increased without increasing the chance of overcrowding. In fully automatic systems, additional capacity can also be quickly added or removed from the system to respond to changes in peak demand or special events, as the system is not dependent on driver scheduling. In UTO systems, more of the vehicle floor space can be freed up for passengers if there is no requirement for a driver’s cab. Some passengers also enjoy the novel experience of riding in the front car. Some form of control panel is provided for manual operations during emergency situations. Safety and AccessibilityUse of ATP in driver-operated rail systems is the accepted industry standard in modern rapid transit applications. Going beyond this to different forms of ATO (with or without on-board service personnel) must consider issues of safety and accessibility both of the rail operations and the passengers using the system. In general, removing the human element increases the safety of the train operations but increases the burden of safety assessment of the whole system. One of the important aspects of automatic train operation is the segregation of passengers from the track. In most instances, this is carried out by platform edge doors at the stations, which prevent local access to the track. In other areas, physical barriers, such as security fences, detection systems and security personnel are used to reduce the ability of illegal entry to the track. Driver-operated systems require less sophisticated security and intrusion detection technology as human operators can detect and report suspicious activity before trouble occurs. In fully automated systems, the triggering of intrusion detection equipment, whether accidental or an actual event, results in system shutdown until the cause can be determined and corrective measures taken. Platform edge doors at stations improve safety and accessibility by defining passenger wait locations for boarding passengers and assisting with passenger flows on the platform. As trains stop at a consistent location on the platform each time, this allows passengers to queue up at the right location every time. This also helps to speed boarding and reduce the chance that a passenger with a mobility device will need extra time to get in position to board the train. Use of platform edge doors is restricted to ATO systems due to the complexity of vehicle alignment with platform door openings under manual operation. While the consistent door locations of automated systems provide predictability for the passenger, it is well understood that the presence of a driver or guard, who is responsible for operating the train doors, can provide a level of comfort and human response to passengers who are having difficulty boarding and hold the doors open for longer periods to allow people to clear the doors. MaintenanceATP, ATO and ATS require operator control centers and additional systems maintenance over driver-operated systems. The additional on-board components and the extra control centre equipment add to the amount of equipment that needs to be maintained. In addition, diagnostics and maintenance of communications equipment also need to be considered. Regular systems testing, in addition to maintenance, will be required to maintain safe operations. For both automated and driver-operated systems there will need to be a regular program of preventative maintenance to complement the minor and major maintenance cycles. CostsCapital costs for automation include the additional on-board equipment, enhanced communications equipment, control centre, control system and dispatch system. There are also initial costs related to system development, testing commissioning and maintenance. When new requirements are added, the system will have to be updated and retested, which can add to costs. Off-board systems include incident management and intrusion detection. These capital costs can be offset by operating cost savings if unattended operation is implemented. The literature is mixed on overall operations cost savings associated with automated systems. Proponents argue that automation offers financial savings due to reduction in staff as well as energy and wear and tear costs because trains are driven to an optimum specification. System ImplicationsDegree of Corridor SegregationThe primary implication associated with automatic train operation is the degree of corridor segregation required to permit driverless operation. By definition, automated train systems must be grade separated from all other traffic to ensure public safety. Without an on-board driver to respond to people or objects in the path of the train, the access must be completely controlled to prohibit trains from coming into contact with those people or objects. Automated systems use intrusion detection systems to determine if someone has accessed track level, or if objects have been placed or landed in the train’s way. SkyTrain has local intrusion detection in the station areas, although this is unreliable in heavy snow conditions and requires manual supervision in extremes of weather. Reports also indicate that it is susceptible to vehicular vibration and false alarms. As this intrusion detection has an important safety function it requires regular testing to ensure correct operation. Single versus Multiple Vehicle-typesAutomation technology can be supplied by the vehicle manufacturer or from multiple sources. In most systems the vehicles and automation technology are combined and supplied as one package to reduce the issues of incompatibility and inter-operability. The system integrator pulls the elements together and provides the transit operator with a complete package that has been thoroughly tested. Given the different corridor segments which together make up the TMP rapid transit network and the constraints which partially-segregated rights-of-way impose on the use of ATO, implementation of fully automated technology will likely require the acquisition of a fleet consisting of multiple vehicle-types to serve those corridors where ATO is not possible. The implications of this are discussed further in the Single versus Multiple Vehicle-type issue paper. Acquisition of a single vehicle-type which can operate under automatic or driver control is possible, and operations involving a mix of automatic and driver operated control are discussed below. Signalling SystemsAs mentioned previously, use of ATP (which is a prerequisite for ATO) is the industry accepted standard for urban rapid transit systems. However, automated systems often use “moving block” signalling rather than fixed block signalling, where the slower a train is going the smaller the “safety zone” becomes and hence the closer it can get to the train in front, this being because at slower speeds they require smaller braking distances between the vehicles as a result of the lower kinetic energy. An important distinguishing feature of driver-operated trains is that in the event of a signalling system failure, they can revert to a degraded mode operation (e.g. line of sight) and maintain service. As the train control and signalling are essentially the same system in automated trains systems, failure of the signalling system will prevent train operations from continuing until service personnel are positioned on each train to provide manual operation. Mixed Driver-Operated and Automated SystemsSeveral rail systems (Madrid, San Francisco MUNI) run with automated sections at the core of the network (both located in tunnels) and driver-operated sections on other corridor segments. This allows for maximum capacity and safety of operations on the busiest corridor segments of the network. At the changeover point, the system transfers control to the driver who accepts and begins to control the train. Similarly at the handover point, the driver would signal for automatic control to be initiated and allow the system to continue operation. In both of these cases, the driver remains on-board and is responsible for opening/closing the doors at stations. These would therefore be considered STO rather than ATO systems. The driver is still required in order to operate the vehicle on partially segregated corridors outside the core area. Theoretically, the driver could leave the vehicle at the handover point, with UTO occurring in the automated sections of the line. Nuremberg (Germany) is currently the only known example of a system that employs both fully automated (UTO) and driver-operated trains running over the same track. The driver-operated line is proposed for conversion to full automation in the future. Platform edge doors at stations are not possible due to the use of driver-operated trains on one line, so an alternative technology has been employed on the platforms to detect any intrusion on the track. There may also be instances where one train requires driver operation due to system failure or the need to transfer driver-operated trains over automated territory to reposition equipment. The systems can be configured to recognize non-automated trains in the system and maintain a safe distance during operation. While this is not a common operation, it does allow for maximum operational flexibility. Applicability to OttawaTMP Network CompatibilityA range of operational situations have been identified, all of which have unique operating characteristics that will influence the ultimate transit technology selected. These situations include:
Transitway/Fully-segregatedThe benefits of the either technology can be maximised on a fully segregated line as line speed can be increased. As there is little chance of intrusion onto the line passenger safety is improved. The passenger will experience very little difference in either operating mode. At-grade/On-street (median)Automatic operation at street level can increase the risk of passenger safety, not through system operation, but through the unexpected behaviour of pedestrians, cyclists or other traffic. Here, driver- operated vehicle have an advantage, as the driver can be trained to drive the vehicle defensively and pre-empt car driver reaction. In severe cases, emergency brakes can be applied to bring the rail vehicle to a halt and minimise any collision. GreenbeltAs with transitway, there is little difference between the two systems of operation. However, the automatic train will require separation from the public through barriers and security fences on either side of the alignment, which may be considered visually intrusive. The number of crossing points in the greenbelt could be limited, which may restrict travel. The security fences would also inhibit animal movements across the corridor and along the greenbelt. Solutions such as underpasses or land bridges can be installed if there are significant numbers of animal movements to be accommodated. ParkwayThe parkway carries the same issues as the greenbelt. Elevated/EmbankmentElevated embankments provide a natural and more pleasing barrier for vehicle running, however they do not fully separate vehicular running from intrusion. The embankment is very visually intrusive but can support some biodiversity. Embankments require regular maintenance and inspection and can be restrictive and give rise to safety hazards for maintenance personnel. Access is normally provided through the embankment as tunnels. UndergroundBoth systems can operate in tunnel areas. The Automatic train will require some from of override or manual control in the event of fire or tunnel evacuation. With driver-operated trains, this could be handled by emergency communications. ConclusionsAn automatic train system, as indeed will any rail system, necessitates a culture shift with regards to design, installation, maintenance and management. This culture shift should not be underestimated and will require significant training, expertise and ongoing reinforcement. Automatic train systems no longer require simple rail maintenance but require rigorous standards and training to ensure the system operates reliably and safely. The complexity of equipment, standards and records are of a higher level than that found in the operation of a road based transit system and will require personnel with skills that are already in high demand. The mission of any urban transit system is to provide safe, reliable, efficient, high quality service to its passengers in a cost effective fashion. To meet this business need, urban transportation systems around the world are increasingly being automated to achieve the following benefits:
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