Making the case for conversion
Conversion from manual to full driverless operation, especially on intensively-used systems that form the backbone of cities, is a hugely complex project that requires careful planning and optimum timing to ensure technical and financial viability.
Existing signalling and control systems have to be upgraded, track protection systems (either platform screen doors or track detection) and rolling stock either needs to be replaced or extensively modified. Correlating the right time to make the switch to match asset life expiry is key to maximising the return on investment, which can be as little as ten years – but the human factor cannot be ignored during this process.
Lessons can be learned from Nürnberg, the first German city to implement such a conversion with upgrades to U-Bahn lines 2 and 3. Driving staff were retrained with customer service qualifications and are now stationed along the two automated lines; this offers the added benefit of giving passengers more points of contact on the system, but these staff also have the technical knowledge to address issues at stations, such as escalator or ticket machine failures – and of course driving in the event of a failure.
While much is often made by labour unions of the implementation of automation, in reality the effect of removing driver operations is usually a positive one with a broadening of the skills base by bringing together previously separate job roles and increasing job satisfaction.
The move to driverless operation in Nürnberg was driven by reducing operating costs; taking the opportunity to automate while re-equipping with higher capacity rolling stock and the facility to take stock into/from service near-instantly according to demand to serve the core section of shared track between U2 and U3. UTO has cut headways in half on U2 and U3, from 200 seconds to 100, and the rolling stock requirement has dropped (46 compared to 54 under manual operation on U1 that is a similar length with the same amount of stations), while capacity has been significantly increased. A mixture of short and long trains are run routinely and can be injected into the system as required by the operational plan given passenger demand, time of day or special events in the city. Energy savings of 15% have been reported.
Against the more usual trend of platform screen doors to prevent either intentional or accidental track access (currently 76% of stations in automated metro lines in operation are equipped with platform screen doors), Nürnberg operator Verkehrs-Aktiengesellschaft Nürnberg chose to mirror the technology used on Lyon’s VAL line D. Track areas at each station are continuously monitored by a high-frequency detection system located below the edge of the platform, with matching receivers mounted along the tunnel walls. These scan up to platform level, spaced at 150mm intervals, and if an object intrudes into the space and breaks two adjacent beams an alarm is triggered.
The system measures the size of any obstruction by counting the number of beams broken. Anything longer than 2m is deemed to be a train, and no alarm is issued. Transmitter failure is automatically reported to the OCC, and until it is reset, an obstruction breaking one beam to either side of the fault will activate the alarm.
Separate modules at platform mid-points detect anything falling between the coupled units of a four-car train; these are mounted at a lower level, with the transmitter in the track by the offside rail, and are only activated while the train is stationary at the platform.
As well as redundancy of driving and operational staff, and especially relevant in a climate of driverless automobile trials, is the recurrent concern of decision-makers around public perception of automated mass transit. However, UITP research suggests that, given the varied cultural contexts in which metro automation has been successfully deployed, this is not a significant barrier to implementation. Indeed, removing the human factor is often seen as a positive move for more reliable and more frequent services with greater capacity.
Another important indicator of this acceptance is that once a city has built an automated metro line, all subsequent lines follow a similar model.
As cities grow, more and more move towards the requirement for 24-hour mass transit services. To serve this changed passenger requirement and growth in passenger traffic, automation and digitisation are key.
Next-generation technologies and cloud-based services allow greater integration of operations and passenger information, while smart data analytics will give more detailed and precise control over infrastructure and vehicle service, and integrated resource management. As surface transport catches up, lessons will also be shared with other modes.
One of the most exciting and technologically advanced current schemes is the mega-project to deliver six fully-automated metro lines for the Saudi capital, Riyadh. The largest mass transit system ever created from scratch at 175km (109 miles), once fully operational the Riyadh Metro will be capable of transporting the equivalent of a small town’s population every hour.
Of course such a project requires the co-operation of many manufacturers and suppliers, and from 2018 Alstom, Bombardier and Siemens driverless trainsets will run at headways from 90 seconds.
With mega-projects such as this underway in China, the Middle East and Latin and Central America – plus conversion of existing lines elsewhere in the world – the future is increasingly looking driverless.
Feature originally appeared in TAUT April 2017 (952).