AT 08.18 on March 4 2010, at the height of rush hour in southern Taiwan, the ground began to shake, buildings moved, and people held their breath.
Earthquakes are not unusual in Taiwan; indeed with the island situated in the Pacific "ring of fire" on the western edge of the Philippine plate, around 22,000 incidents of seismic activity are reported every year, 500 of which are noticeable. However, the scale of this event was unprecedented in recent memory.
Measuring 6.4 on the Richter scale at its epicentre in the heart of the mountainous area of Kaohsiung county near Jiashian, it was the largest earthquake in the region since 1900, causing damage to buildings and temporarily disrupting electricity supply to 545,066 homes and businesses.
Thankfully no-one was killed in the incident and the casualty list of 97 might have been higher if suitable precautions had not been taken to protect key pieces of infrastructure.
This includes Taiwan's high-speed railway network, which was operating six passenger trains in the impact area at the time of the earthquake.
Anything above 4 on the Richter scale automatically triggers an emergency brake application. And while five of the trains were stopped without incident, the lead bogie on T110, which was 47km from the epicentre and travelling at 298km/h at the time of the earthquake, derailed after the emergency brake was deployed. This happened one to two seconds after the automatic train control (ATC) stop signal was received, with the derailment occurring at 273km/h. The train came to a halt after 68 seconds, or 3.3km down the track, without causing injury to passengers.
The derailment inevitably damaged the line's slab track, while two sections of overhead catenary were destroyed by the force of the quake. However, following a three-step recovery programme, full bi-directional services were restored to the line within three days of the earthquake as Taiwan High Speed Railway Company's (THSRC) disaster management strategy and recovery procedures came into force.
The frequency of natural disasters and extreme weather in Taiwan substantiate THSRC's claim that it is the most vulnerable railway in the world. In seven years of operations, the network's disaster warning system (DWS) has issued alarms for earthquakes on 162 occasions, or 23 times a year, and on 10 occasions operations have been stopped for more than 30 minutes. The island also suffers from typhoons, and THSRC has faced 38 such warnings since it began operating in 2007, enacting its emergency operations centre (EOC) on 25 occasions with operations halted seven times.
Mr Alex Chang, chief operating officer of THSRC, says the emergency management strategy follows a philosophy of preparation, response, recovery and mitigation to deal with whatever Mother Nature might throw at it.
First and foremost the railway's infrastructure was designed with the potential impact of extreme weather and natural disasters in mind. Seismic design principles have been incorporated such as the use of elastomeric bearings on bridge piers and viaducts which use extra reinforcement, and shear keys and structural movement joints.
The structures are also designed to withstand horizontal winds with a force of up to 3.8kN/m2, and allow permissable operations to continue in 1.5kN/m2 winds. Similarly a proven catenary and pantograph interface fit for typhoon conditions is in use which can withstand wind speeds of 55m/s. In addition both longitudinal and transverse drainage appurtenances are used with a drainage run-off coefficient of 1.0 to minimise the impact of erosion and scouring from fast moving rain and river water during and following a typhoon.
THSRC's preparation and response efforts are aided by the use of a network of detection and diagnostics systems which comprise DWS. Detectors measuring heavy rainfall are installed at 18 locations along the 345km line along with 43 flood level and 21 wind velocity sensors, which are all connected to the signalling equipment room and operations control centre (OCC), and depending on the severity of an alarm, can force speed reductions or trigger an emergency stop signal. For example a Level 2 rain alarm will reduce the maximum operating speed to 170km/h, Level 2 wind imposes a 120km/h restriction, and in floods operating speeds will fall to 70km/h. In Level 3 rain speeds are reduced to 70km/h, while a Level 3 wind and flood alarm stops operations immediately.
Similarly 71 landslide, 94 rock fall, and 32 intrusion sensors are situated in the track wayside, which if triggered immediately issue an emergency stop signal to trains and an alarm to the OCC or EOC.
Earthquake detection stations are also located in the vicinity of the line, with 11 primary stations each with a range of 30-35km in place, along with 40 secondary spots. Two types of sensor are used at each of the primary stations: an electronic sensor which issues a Level 1 alarm for an earthquake of 4 on the Richter scale, Level 2 for a force 5, and Level 3 for a force 6, while a mechanical type issues an alarm for a force 4. Each of these detectors is connected to the train control system network via the ATC ground system as well as the DWS to alert the OCC.
Following the Jiashian earthquake and derailment, a review was undertaken of the existing detection system in an effort to reduce the time it takes to trigger emergency brakes. As a result 13 additional sensors were installed in existing wayside signalling units. And as Mr Lawrence Chi Ming Tam, senior engineer in the system engineering department, at THSRC, revealed at the first UIC conference on Natural Disaster Management for Railway Systems in Taipei in May, the project was concluded in April and has reduced the density of the detection locations from 30-35km to 10-15km.
"Although the advanced warning time is only reduced by a few seconds, and results in limited train deceleration improvements, every single second we can save contributes to risk reduction," Chi Ming Tam says.
While it remains impossible to predict earthquakes, THSRC can track typhoons in advance of reaching land, and prepare the railway, its staff and passengers for the expected impact of such events on operations.
Chang says that there is a three stage response to a typhoon. The first stage is initiated by sea warnings issued by Taiwan's Central Weather Bureau (CWB), at which point the OCC and some staff check the system data and provide feedback on pre-inspections of typhoon prevention measures.
"We then look to estimate the start of an 18-hour window before the typhoon arrives on land, which provides us with time to prepare as we transition to the second phase," Chang says. "At this point we ask each department to dispatch staff to certain locations where they can observe and manage operations, and ask staff in the EOC to check the readiness of the warning systems, initiate special inspections, and mobilise necessary resources. Eight hours before the typhoon lands we set up a company-wide EOC, where all divisions of the company dispatch their key personnel to sit in to discuss the operation strategy where key decisions are made as the storm progresses."
In addition to the DWS, the OCC and EOC can also monitor the position and movement of staff and vehicles. As a result there is an emphasis on keeping staff connected and using their observations to inform the decision making process. Mobile phones are the primary form of communication, utilising 4G and 3G connections where available, with 2G in use in more remote areas which supports voice and text messages.
Mr Tommy Jen, THSRC's deputy director of the OCC, informed the Taipei conference about a mobile application used by all staff, which provides live timetables and duty information, the latest versions of the company's manuals and bulletins, and live maps, which incorporate Google Street View.
"Traditional voice communications are often not enough to provide an accurate picture of what is going on, especially in emergency situations," Jen says. "We are using interactive multimedia platforms which support text, photographs, location services, audio and video so we can get the most comprehensive report about the situation. Using streetview for example can show potential hazards and conditions for passengers following an evacuation, such as if you have to cross a busy highway, which would require the police to stop the traffic."
Direct communications links are also in place with emergency service providers, cooperation with which is integral to coordinating THSRC's recovery strategy. Staff from the Bureau of High Speed Rail (BHSR) also provide assistance during emergencies, while agreements are in place with governments of 11 counties along the line to provide resources and support.
For full-scale evacuations, THSRC has contracts with 92 local shuttle bus companies which can travel direct to 192 designated exit points along the railway and were deployed to evacuate 2375 passengers during the Jianshian earthquake. In areas where road access is difficult, THSRC has contracts with helicopter companies which can evacuate a limited number of passengers and also allow engineers and managers to observe and assess suspected landslides and other issues which may have jeopardised the railway. Unmanned drones are also being used to monitor conditions in areas difficult to reach along with CCTV which is deployed along the line.
Communicating with its passengers is another major element of the response strategy. Chang says if THSRC needs to cancel services it aims to do this two hours before that particular train is scheduled to depart. In addition to posting information on its website and briefing staff at its ticket offices and call centres on the latest situation, THSRC regularly sends service status notifications to the 9000 convenience stores throughout the country from which its tickets are sold. Similarly its mobile phone booking service, T Express, is capable of distributing messages to passengers about the status of services and to offer travel advice. At the station 55-inch multimedia screens display the latest travel information.
THSRC also maintains a close relationship with media channels, communicating directly with television and radio station editors at times of crisis so that they might be able to distribute the latest information to as many people as possible.
However, communication to passengers on trains was criticised in the aftermath of Jiansian. While the EOC was set up within 12 minutes of the earthquake, the process of evacuating the 2375 passenger took more than four hours. THSRC was also scrutinised for its apparent poor communication with the passengers.
"The OCC didn't provide sufficient information to the train crew about the earthquake which they could then pass on to passengers to put them at ease," says Ms Irene Chen, senior specialist at the station operation department of THSRC. "They were able to gather more information from using their own smart phones."
Chen says procedures to enhance communications between the OCC and train crew are now in place, while other improvements were carried out including introducing temporary ramps to aid disembarkment during an evacuation, and the use of nets to block doors which may be opened to improve ventilation.
The performance of the shuttle buses was also addressed. Chang says that it became apparent in the aftermath of the earthquake that many drivers were not familiar with the designated meeting points and some did not know the roads around the exits.
He says solutions were identified during the company's scheduled review of its response to the incident held two weeks after the event. These meetings are an opportunity to suggest changes to regulations, staff training and equipment and it was decided to develop a new map that could be distributed to the drivers and to set up a common meeting point where station staff could brief them about the situation and conditions they might expect along the route.
Chang says that constantly reviewing its performance helps THSRC to remain as prepared as possible. Clearly it is difficult to predict how certain weather systems and natural occurrences will impact operations and he says the only thing that THSRC can do is prepare as best it can for the worst possible scenario. Its exemplary safety record despite this consistent threat is testimony to the levels of preparedness across the organisation - from the top management in the EOC, to station staff and people selling tickets at convenience stores. And its continuing efforts for improvement indicate that complacency is not an option.
"It is never an easy situation," Chang says. "But I am very proud of my staff and their performance in emergency repairs and recovery."