Safety
News
18th EDITION / ISSN 1793-1665 MAR 2011
SAFETY IN
EXCAVATION
Featured Articles
02 Safety Measures for the Double Wall Cofferdam Construction in the Sea
04 Tunnel Safety
07 Thematic Exercise on “Safe Lifting Operations” at LTA Worksite
09 Achieving the Watermark Award and Beyond
11
Safety Features of Downtown Line Trains
13
Road Safety Reviewer Accreditation Course
SAFETY MEASURES FOR THE DOUBLE WALL COFFERDAM CONSTRUCTION IN THE SEA
Introduction
The Marina Coastal Expressway (MCE) Contract 485 involves the
construction of a 700m dual 5-lanes expressway of which 420m
of the tunnel is built 20m under the mean sea level at the Marina
Channel.
Methodology for Double Wall
Cofferdam Construction
Tubular pipe piles were driven into hard ground to create a
robust temporary earth retaining structure. Installation work
commenced from the land side at Marina East using the guide
frame and vibro-hammer. It then progressively advances towards
the sea section. Crane mats which are made of structural steel
members were placed on top of the double wall cofferdam to
serve as a working platform for machinery used to install the
tubular pipe piles in the sea. Material barge storing the tubular
pipe piles and crane barge were also mobilised for the work.
Figure 1: Aerial view of MCE Contract 485 taken in April 2010
The temporary earth retaining structure system consists of two
rows of tubular pipe piles for the undersea tunnel construction.
This double wall cofferdam retains the earth and prevents the
sea water entry into the work site which provides a dry area for
the execution of ground improvement work, foundation work,
excavation work and tunnel structure work.
Figure 4: Earth Retaining or Stabilizing Structures (ERSS) layout for
Stage 1 cofferdam
This article will explain how the installation of temporary works is
carried out and the safety measures implemented for the double
wall cofferdam construction in the sea.
Staged Construction
The undersea tunnel is constructed in two stages to avoid
causing disruption to the water discharge from Marina Barrage
into the sea and to allow small crafts and vessels to access into
Marina Bay. Stage 1 cofferdam construction in the sea began
in June 2009 and was completed in December 2009. Stage
2 cofferdam construction would commence after the Stage 1
tunnel is completed.
Figure 5: Cross-section view of double wall cofferdam
Figure 2: Artist impression for Stage 1 cofferdam
Figure 6: Stage 1 double wall cofferdam construction in progress
Figure 3: Artist impression for Stage 2 cofferdam with completed
Stage 1 tunnel
Figure 7: Stage 1 double wall cofferdam completed in December 2009
2
Lifting shoe
Lifting shoe capacity: 68 ton
Max. weight of pipe pile: 39.5 ton
Figure 8: Installation of tubular pipe pile in the sea
Figure 12: Ensure sufficient lifting Figure 13: Reinforce the top of
shoe capacity is provided
pipe pile by welding
of additional stiffener
plates at lifting points
Safety
provisions
for
heavy lifting work include
ensuring that sufficient
capacity for the lifting
shoe, lifting angles are
provided and lifting points
are strengthened.
Figure 9: Lifting and shifting of crane mat as pipe pile installation
progresses
Figure 10: Deck beams and panels replaced the crane mats to serve as
a working platform for next stage of work
Figure 14: Ensure sufficient lifting angles
are provided
Figure15: Daily check on the
vibro-hammer clamps
by the competent person
before operation
Figure 16: Training on the use of
life vest
Safety and Risk Mitigation Measures for
Double Wall Cofferdam Construction
For the installation of pipe piles, vibro-hammer clamps are
checked daily by a competent person. Workers are also educated
on the use of life vest while working at the sea section.
The major risks involved in the cofferdam construction include
lifting work, installation of tubular pipe piles and working in the
sea.
Some safety provisions for works in the sea include the provision
of proper working platform and fixing of blinking lights on
barges to warn nearby vessels at night.
Some safety provisions are illustrated below –
Figure 17: Provision of working
platform for hot works
in the sea
Figure 11: Safety provisions on the crane mat include life buoy, guard
rail and blinking light
All working personnel were required to put on life vest when the
double wall cofferdam was still under construction. A safety boat
is always on standby for any emergency rescue operation.
Figure 18: Provision of blinking
lights on perimeter of
barges to warn nearby
vessels at night
Tan Wee Thong
Project Engineer
MCE C485
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TUNNEL SAFETY
Introduction
Tunnel construction is generally considered to be more hazardous
than other construction works carried out above ground. The
confined working environment, absence of natural light and
ventilation, with use of heavy machinery create additional
occupational safety and health hazards for site personnel.
Safety Personnel
The LTA’s contractors are required to engage adequate numbers
and suitable levels of competent staff with relevant tunnelling
experience to provide the required level of expertise to complete
the tunnelling works in a safe and professional manner.
For every 25 or more workers working underground at any one
time, the occupier has to ensure that at least 5 of the workers
are trained in rescue, resuscitation, use and maintenance of
breathing apparatus and fire fighting equipment.
Control of Access and Egress
TUNNEL SAFETY
During any emergency it is important to ensure all underground
workers are safely evacuated to surface. In the event that
someone is trapped underground, it is important to be able
to locate the worker. To account for every site personnel, a
tally board at each entrance to the underground work place is
displayed and updated with the names of persons working in the
tunnel and their work locations.
Figure 1: Tunnel construction in process
Any person undertaking underground construction works on
Land Transport Authority’s (LTA’s) projects must be familiar with
the following documents –
1. LTA General Specification Appendix A: Safety, Health &
Environment
2. LTA General Specification Appendix O & P: Tunnelling and
Tunnelling Machines
3. LTA General Specification Appendix H: Requirements for Site
Electrical Installations
4. Workplace Safety and Health (WSH) Regulations – all aspects
applicable to tunnelling works
5. British Standard BS 6164: Safety in Tunnelling in the
Construction Industry
6. HSE 1996 & 2001 Recommendations for Working in
Compressed Air
This article will touch on some of the safe practices adopted in
LTA worksites for tunnelling work.
Training
The confined working conditions and engagement of
mechanized tunnelling requires a well-experienced team with
trained supervision and support from the management.
All workers employed in tunnelling works must attend the
Construction Safety Orientation Course (Tunnelling) conducted
by the Ministry of Manpower (MOM) and shall be trained in the
operation of equipment and the safe working procedures.
4
Figure 2: Tally board at entrance to tunnel
Communications
To assist daily operations and in the event of an emergency
accident or incident, an effective and reliable means of
communications such as a telephone network needs to be
installed and maintained at all times at the following locations:
•
•
•
•
•
•
•
•
•
Guardpost;
Working chamber at the face of an excavation;
At intervals of 100 metres along the tunnel;
Working chamber side of the manlock near the door;
Interior of each chamber of the manlock;
Lock attendant’s station;
Compressor plant;
First aid station; and
Outside the portal or at the top of the shaft.
Figure 3: Telephone network communication
Lighting
All lighting levels in tunnels shall be adequately illuminated at
not less than 100 lux. Emergency generators shall be provided
to ensure adequate illumination of the tunnels and work areas in
the event of a failure in the normal power supply.
In addition, battery-powered emergency exit lights are necessary
for emergencies which shall have sufficient capacity to provide
power for the emergency exit lights for at least 2 hours in the
event of power failure.
Ventilation & Airborne Contaminants
Figure 4: Fire point in tunnel
Welding and cutting can generate sufficient heat to ignite
combustible materials. Gases such as methane can also seep
into the tunnels, creating fire and explosion hazard. Therefore,
a permit to work system is essential for any hot work in tunnels.
A fire emergency procedure approved by the Singapore Civil
Defence Force (SCDF) must be displayed at prominent positions
inside and outside each tunnel.
Fire fighting facilities inside tunnels must include a fire alarm
system that is connected to the ground level. There should be
sufficient number of dry chemical fire extinguishers and water
supplies allocated with adequate maintenance and checks.
TUNNEL SAFETY
The sensitivity and susceptibility of individuals to airborne
contaminants varies, therefore it should not be assumed that
conditions safe for some individuals will be safe for others. The
best practice is to maintain concentrations of all atmospheric
contaminants to as low as reasonably practicable and below the
Permissible Limit Level (PEL) as stipulated in the WSH (General
Provisions) Regulations.
To prevent asphyxiation due to inadequate supply of air, the air in
all work areas underground must contain at least 19.5% oxygen
by volume. Tests for oxygen deficiency must be conducted
before the commencement of works and thereafter at 4-hourly
intervals. Oxygen-enriched atmospheres are as hazardous and
can cause combustible materials to burn more freely, therefore
oxygen levels should not exceed 23.5% by volume.
Fire Safety
In a confined area such as a tunnel, the importance of fire
prevention is of greater significance. The amount of combustible
materials and gases present underground should be kept to
the minimum and suitable fire-fighting equipment should be
conspicuously located nearby.
Figure 5: Fire fighting facility in tunnel
Clearances, Walkways and Refuge Areas
safety news
The exhaust fumes of petrol engines can contain up to 10%
carbon monoxide and should never be used underground.
Diesel engines can only be used if no fumes or sparks are
emitted and no air enters the engine without first being cleaned.
Gasoline, liquefied petroleum gases and other highly flammable
substances shall not be stored or used underground.
The use of heavy machinery and rolling stock in a confined
space creates a potential hazard of serious injury. LTA specifies
that there should be fitted an elevated walkway maintaining a
separation between workers and by locomotives or other mobile
equipment in a tunnel.
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safety news
Figure 6: Elevated walkway
Risk management to address crushing and entrapment should
be carefully evaluated. Warnings, refuges and procedures shall
be established; complemented by thorough training to prevent
such occurrence.
Rail Operations
Tunnel tracks typically follow a gradient. If the brakes of a
locomotive fail, the train will start to move uncontrollably unless
the train’s motion has been effectively halted by the deployment
of wheel chocks/stops. The train will gather speed and unless
the loco driver can get the train back under control, or there is a
device such as a Manchester gate at the portal to bring the train
to a halt and prevent further travel, it will continue all the way
down along the temporary track and this could potentially cause
derailment and cause impact to workers and machinery.
Figure 8: Monitor site conditions from site office through CCTVs
Emergency plans need to be thoroughly disseminated to all
workers through safety induction and familiarization tours on
site. A culture of safety can be enhanced by in-house training,
communication through toolbox meetings and display of
procedures and escape plans on notice boards.
All stakeholders should be involved to develop an open
safety culture. Accountability for safety performance must be
appropriately allocated through the entire safety management
process, in particular to the emergency plans. As a minimum,
table top exercise and regular drills shall be conducted once
every six months.
Figure 7: Manchester gate installed to prevent overrun of train.
Emergency Planning & Mitigation of Risk
Emergency planning and mitigation of risk through a systematic
risk management process is essential to ensure safety of tunnel
workers and other stakeholders of the tunnel project.
Figure 9: Emergency drill conducted with SCDF
Summary
Tunnel construction may present many hazards. However, with
the implementation of safe working procedures, and with
additional precautionary measures in place, one can be sure
that the risk can be reduced to its minimum and work can be
accomplished safely.
Blaise Pearce
Senior Project Manager
DTL1 905
6
Thematic Exercise “Safe Lifting Operations” at LTA Worksites
Introduction
In 2001, LTA introduced a new initiative known as “Thematic
Exercise” aimed at improving its safety performance. The
exercise focuses on a specific theme with thorough evaluation.
Potential weaknesses identified would be brought to the
prompt attention of all of our contractors for their immediate
rectification, thereby eliminating the likely occurrence of an
accident. Such pro-active exercise complements the regular
site inspection regimes carried out by the various levels of the
project team and enabling LTA to seek continuous improvement
to its safety performance.
• The contractors had appointed sufficient numbers of
competent Lifting Engineers who coordinated all lifting
operations that are supervised by the lifting supervisors. The
Lifting Engineers also formulated and prepared lifting plans to
ensure that the cranes’ accesses and ground conditions
(footing) are taken care of with due considerations for the
stability and siting of the cranes.
• The contractors had also assessed the competency and
qualifications of the lifting team, i.e. crane operator, rigger,
signaller, lifting supervisors etc. to ensure that they possessed
the necessary safety knowledge and skills to perform the
intended tasks safely before appointing them in writing to be
in the lifting team. These key personnel were easily recognizable
as they wore identification vests on site.
Figure 1: Thematic exercise scheduled against construction phase
Figure 1 above is an example of the approach in the scheduling
of the themes for the respective exercises. The theme-based
exercises are pegged to the various phases of construction
works on site. Through focusing on specific risks identified at
each phase, these exercises zoomed in to ensure that risk
control and mitigating measures are in place and complacency
does not set in. It also helped to increase the safety awareness
of contractors and their workers for their full compliance to the
legal requirements and our General Specifications (GS).
During the last quarter of 2010, Safety Division conducted
thematic exercise at Downtown Line 2 (DTL2) project. The
theme, “Safe Lifting Operations” was chosen as the project
was still largely in its excavation phase, with extensive usage of
Lifting Machines (LM). This article aims to share some of the
salient findings of the thematic exercise carried out.
Figure 2: Lifting team wore identification vests on site
safety news
Key findings
Good Practices/Compliances
•
About 30 LM were randomly picked but thoroughly checked for
compliance to the legislation and our GS requirements. Safety
Division noted that many of our contractors are now more aware
of our stringent requirements and have put in concerted efforts
to comply with the legal and contractual requirements. In this
exercise, some of the notable findings were as follows:-
• The auxiliary load-lines were tested by Approved Examiners
(AE) and the results reflected in the LM Certificates.
• All the LMs being checked were found to be less than 15 years
old and inspected by an Approved Examiner within the
6-month inspection frequency, as stipulated contractually;
Appropriate communication system between the crane
operator and the lifting teams via walkie-talkie were in placed.
In situation where communication system was not available,
the signaller would position himself in a safe manner to
maintain visual contact with the crane operator.
• All LMs operated within the Safe Working Load (SWL) as
specified in the LM Certificates.
• There was no visible structural damage of the LMs used on sites
and their safety switches were generally found to be
acceptable and in good conditions.
• Monthly colour coding system for all lifting gears were in
placed to ensure that the LG are regularly checked and paintmarked monthly before they are being used on sites.
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safety news
Figure 5: Externally fitted visual/audible alarm
Figure 3: Monthly checks on LG and colour-coding by contractors
• All lifting zones were clearly demarcated and cordoned
off, with warning signs prominently displayed to prevent
unauthorized entry.
Areas for improvement
Two areas of concern were indentified as follows:
• Some LMs still have their load charts displayed inside the
crane cabin not translated into languages easily understood
by the crane operators; and
• One LM was spotted with its boom length different from
the readings shown in the Load Radius Indicator (LRI). All
LRI are to re-calibrated whenever there is a change in the LM
configurations.
These areas of concern were promptly highlighted to our
contractors for their corrective actions.
In addition, Safety Division conducted a series of briefings to
all lifting supervisors, project teams as well as our Qualified
Persons’ (Supervision) teams of DTL2 project in Dec 2010 / Jan
2011. About 300 personnel attended the sharing sessions on the
findings of the thematic exercise.
Figure 4: Demarcated lifting zone with warning signs in placed.
•
Proper foothold and access to crane cabin are provided for
crane operator.
• All LM had an additional audible alarm fitted externally to
raise attention to nearby workers of its presence and to keep
away from the demarcated zone.
Figure 6: One of the sharing sessions held on site
Conclusion
Our continuous efforts in conducting such thematic exercise
are well received by project teams as well as contractors. LTA is
confident that such exercises and sharing sessions would help
to achieve greater level of safety for the construction industry.
Tan Jway Kwee
8
Safety & Health (Enforcement) Manager
Safety Division
Achieving the watermark award and beyond
Introduction
On 30th September 2010, LTA joined a list of distinguished
organisations and individuals who have made significant
contributions towards Singapore’s water cause by clinching the
prestigious Watermark Award from the Public Utilities Board
(PUB).
Good Planning
All activities and sequence of works are planned in advance,
giving due considerations to the impact they may have on the
environment. Wherever feasible, land clearance is carried out in
stages. This minimises the amount of bare earth surfaces that are
left vulnerable to the effects of rain.
Contractors also engage Qualified Erosion Control Professional
(QECP) to advise them on the necessary earth control measures
(ECM) that must be implemented before any earthwork can
commence. This is to ensure that all works to be carried out
in the immediate phase have been considered and that the
controls put in place can adequately cater to the amount of silt
generated. The QECP shall review his initial ECM plan at least
once a month (recommended) or when the works move into a
different phase.
IMPLEMENTATION OF GOOD PRACTICES
Effective Erosion and Sediment Control
Figure 1: Proud recipients of the Watermark Award posing for a group
photo with the Guest-of-Honour: Dr Yaacob Ibrahim, Minister
for the Environment and Water Resources
This was made possible through the concerted efforts of various
Groups within LTA and support from our contractors.
The high visibility of our projects and as one of the largest public
developers in Singapore, LTA is well positioned to influence the
construction industry and the public to do their part in protecting
and conserving water. As a recipient of the Watermark Award,
we have an added responsibility to be a role model for other
organisations in Singapore. We can achieve this by:
Upholding our high standards in managing and protecting
our water resources
•
Promoting good water conservation practices through active
participation in seminars, conferences, workshops and sharing
sessions
•
Encouraging an innovative culture and collaborating with
other agencies
This article aims to share with readers LTA’s measures in managing
and protecting our water resources on our construction sites, in
our journey towards achieving the Watermark Award.
Protecting Our Water Resources on
Construction Sites
LTA has a sound environmental management system to effectively
manage impacts arising from our construction activities. In
general, LTA adopts the following approach to manage our
water resources at construction sites:
•
•
•
•
Good Planning
Implementation of Good Practices
Monitoring
Education
For exposed work areas, erosion control blankets or canvas
sheet are used to cover these areas at the end of each work day
and before a rainfall.
safety news
•
All vehicular access routes in LTA sites are concrete-paved where
possible. This immediately reduces the surface area of bare
earth and limits the effects of erosion. Concreting also has a
lot of other environmental benefits such as eliminating ground
depressions which can breed mosquitoes. Dust generation can
also be considerably controlled with reduced bare earth.
Figure 2: Implementation of the “Brown to Clear” bio-ball filtration
system on site and treating silty water with a treatment system
at the final discharge point
While a set of good erosion control measures is the first line of
defence against silt discharge, sediment controls aim to capture
and retain silt within the site for treatment so that only clean
water (of TSS, Total Suspended Solids < 50mg/L) is allowed to
be discharged.
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safety news
Water Pollution Control
LTA enforces the use of spill trays for diesel-operated equipment
and at each diesel transfer point. Additionally, all machinery on
sites have to be inspected and serviced on a regular basis to
ensure that they are in good working conditions.
Monitoring
To ensure that the above measures and good practices are
strictly adhered to, LTA carries out a monthly environmental
assessment on the contractors using the Environmental Safety
and Security (ESS) Annex of Environmental form. This gives an
indication of the site’s performance for that particular month
and identifies areas for improvement. The quality of the treated
water is also monitored at every final discharge point using a TSS
probe and a CCTV. This allows the contractor to immediately
stop the discharge of water into public drains if the allowable
limit of 50mg/L is breached.
Education
Educating the Workforce
LTA believes in educating and raising awareness amongst
the workforce as the foremost approach in managing the
environment.
Figure 3: A diesel storage tank is contained within a bund wall to prevent
spillages or leakages into our waterways
A diesel storage tank on site has to be placed within a concrete
bund wall with a capacity that is at least 110% that of the largest
tank stored within it. This is to ensure that the concrete bund
wall can adequately contain any leakages if a rupture occurs.
Recycling of Water
The treatment units at the final discharge point produce treated
water that is clean and can be recycled for other uses. Besides
being able to conserve water, this approach also provides
contractors with some cost savings.
LTA strongly encourages the reusing and recycling of water
on site. Most contractors will reuse treated water at vehicular
wash bays or for wetting the ground before work commences.
Treated water from the membrane treatment units can even be
used to water plants.
A proactive supervisor can influence the behaviour of his workers
under his supervision. A worker’s simple act of choosing not to
litter but to bin his packet drink properly can go a long way in
maintaining the cleanliness of our waterways.
To reach out to the workforce, LTA has produced several
environmental guidebooks and posters which are prominently
displayed on site. Through daily toolbox meetings,
environmental campaigns and even rewards for exemplary
workers, environmental messages are constantly communicated
across to all site personnel. Safety Division also conduct the
environmental awareness training course twice a year to train
site staff to supervise environmental matters on site.
Conclusion
Singapore’s water demand is expected to double in the next 50
years. Even though two-thirds of Singapore will become water
catchment by the end of this year, it is still not sufficient. The
NEWater capacity needs to be tripled while the desalination
capacity will have to increase by almost 10 times.
This growth in water demand is expected to come from nondomestic users, hence it is imperative that organisations
emphasize on the protection and conservation of water resources
in their daily operations.
The achievement of the Watermark Award is an affirmation and
recognition of the commitment LTA has towards Singapore’s
water resources. It is now LTA’s role to act in its capacity to
influence and inspire other organisations to do their best in
protecting and conserving our precious water resources and
likewise, become the next Watermark Award recipient.
Mataias Chew Boon Bwan
Environmental Manager
Safety Division
Figure 4: Storage of treated water on site for future use
10
S afety features of downtown line trains
Brake Control System
DTL trains utilize EP2002, a mechatronic braking system that
integrates brake electronics with pneumatic valves to provide
service braking, emergency braking, and wheel slide protection
within a single compact unit.
The EP2002 valve units are
connected in a network
throughout the train and
communicate with each
other so that in case of a
faulty unit, braking effort is
redistributed through the
remaining bogies.
Introduction
The first two trains for Downtown Line (DTL) will shortly
commence testing for a period of 18 months in Changchun,
China. The trains are designed in Hennigsdorf, Germany, and
built in Changchun, China, by Changchun-Bombardier Railway
Vehicles Co. Ltd. In total, 73 driverless automatic trains will be
built for the 40km underground line.
Being a driverless system, like North-East Line and Circle Line,
DTL is designed to the highest safety and reliability levels.
This article aims to highlight some key safety design features
included in the DTL trains.
Crashworthiness Design and Simulation
Although the train is fitted with train-borne Automatic Train
Protection (ATP) signaling equipment to prevent train collisions,
its car body is designed to withstand crash scenarios in
accordance with EN15227, the European standard for railway
vehicle crashworthiness.
The pneumatics of the train
brakes are configured to
provide safe braking and
continued running in the
Figure 2: Brake Control Unit
event of an air leak. Trains
with defects will still be able to move and stop at the next station
where passengers will be able to exit with minimal disruption.
Emergency braking is triggered when the emergency braking
electrical loop is de-energized. This occurs during critical
operational situations such as obstacle detection on the track
and train car separation. Brakes will be applied at emergency
brake pressure, which is higher than the usual service braking
pressure. This allows the train to stop as fast as possible.
Fire & Smoke Protection
To prevent the occurrence of a fire on the train, strict fire
requirements in line with internationally recognized standards
are put in place. Materials used to build the train are chosen
carefully to ensure that in the event of a fire, they have low
toxicity, low flammability and generate minimal smoke.
Smoke detectors are installed within the air circulation ducts
of the saloon. Heat detectors, also known as fire wires, are run
throughout the equipment cubicles. Once exposed to heat, the
alarm signal will be triggered.
Anticlimber – corrugations engage
in a collision to prevent mounting
Crash Absorber –
deformed after impact
Figure 1: Anticlimber and Crash Absorber after Crash Test
All car ends have anticlimbers installed. In case of a collision,
the anticlimber corrugations of the colliding train cars are
designed to interlock and prevent the train cars from mounting
one another. Additionally, at the ends of every train, an energy
absorbing device is installed behind the anticlimbers.
When a fire develops within the saloon, emergency ventilation
flaps open, allowing smoke to be expelled out of the train.
Should smoke be detected in the fresh air inlet, the fresh air
flaps are closed and interior air is re-circulated to prevent smoke
accumulating in the saloon. An analysis of smoke emission
during an interior fire was carried out to determine the optimum
flap position using computational fluid dynamics software.
The train is also designed to withstand an underfloor fire for at
least 45 minutes, which is duration sufficient for passengers to
evacuate the train safely. Under the car body floor, a sandwich
of stainless steel and insulating material is installed to function
as a fire barrier. Intumescent coatings and sealants are used
at all joints, openings, and exposed aluminium surfaces not
covered by the fire barrier. The intumescent coating swells at
high temperatures to create a thermally resistant foam coating,
enhancing the fire protection provided by the fire barrier.
A “metal knife” type technology will be used on the crash
absorber of the DTL trains. This technology deforms the crash
absorber by cutting through material, thus absorbing energy
impacted on the train. The crash absorber performance was
verified in an impact test with a 80 tonne concrete-filled wagon,
and the overall crashworthiness design validated by Bombardier
using state of the art LS-Dyna crash simulation software.
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safety news
The DTL detrainment door is
deployed during endurance
testing,
simulating
worst
case tilt due to curved track.
The endurance test has been
specified by LTA to ensure
that the detrainment door
has high reliability and can
be depended upon in an
emergency.
Figure 3: Fire barrier and intumescent coating after fire test
Power Loss
In case of power loss from the third rail, the trains have
batteries on board that provide backup power to the lighting,
communication, and ventilation systems for up to 60 minutes,
allowing the Operations Control Centre (OCC) to assess the
situation on board before determining an appropriate response.
Figure 5: Detrainment Door
Assembly
The detrainment door provides
an avenue for passengers
to escape onto the tracks
during emergency. The door
is locked under supervision
of ATP. Before it is deployed,
ATP ensures safe conditions
are met for detrainment. After
deployment, the door can
be re-stowed by one person
in under 10 minutes to allow
quick resumption of services.
Train Communication System
Doors
DTL trains use electrically operated sliding bi-parting doors to
allow passenger boarding and alighting.
The doors have a ‘push-back device’ that allows the doors to
spring back to their original position when pulled back (by
up to 50mm per door leaf). For large objects, there will be a
difference detected in the driving motor current and this will
cause the doors to reopen momentarily. This reopening allows
for the withdrawing of any obstacle.
If any train door is damaged, it is possible to mechanically lock
the door set to prevent accidental door opening during service.
One doorway per car allows for crew access from the train
exterior in case of emergency.
At the bottom of the door sill, a platform gap filler rubber pad
is installed. This pad serves to reduce the gap between the
train and the platform to reduce the risk of feet or legs falling
into the gap, and its size can be adjusted to achieve an optimal
compromise between gap minimization and the filler pad
impacting against the platform screen doors as a train enters
the station.
As operational staff will not be stationed on every train, an
intercom system is installed in the Passenger Emergency
Communication (PEC) unit for passengers to communicate with
OCC staff when needed. There are four PEC units per car, one at
each pair of doorways.
There is also an on board Public Address system to allow OCC
to broadcast important audio messages. CCTV cameras are
installed in each car to record images within the train at regular
intervals. Video recording is activated upon certain safety critical
alarms or actions.
Train Integrated Management System (TIMS)
TIMS comprises train-borne software and equipment that
monitor the overall health status of train equipment. It sends
alarms to the OCC when events and equipment faults occur.
Most importantly, TIMS coordinates the activation and
deactivation of train equipment in response to events. For
example, when a fire is detected, TIMS sends an alarm to OCC
and switches the CCTV in the affected area to high speed video
recording. OCC will then be able to view the camera feed to
determine an appropriate course of action.
Detrainment Door
Conclusion
The concerns faced in planning for the safe operation of DTL
trains are neither new nor unique, for they are faced by every
railway system around the world and many solutions exist.
With the safety provisions mentioned in this article, trains
can operate even more safely and reliably under driverless
conditions.
These safety features will operate in tandem with those of
trackside signaling and station platform facilities to ensure the
safe operation of the Downtown Line metro system.
Ong Wah Wei
Figure 4: Door sill gap filler assembly
12
Engineer
Rolling Stock
Road safety reviewer accreditation course
Introduction
The Road Safety Reviewer Accreditation Course was first
introduced in Land Transport Authority (LTA) in 1999. A total
number of 174 students have obtained accreditation so far.
The primary objective of this course is to raise the knowledge
and understanding of road safety engineering principles in
Singapore. The course also aims to train staff and external
consultants to be Accredited Road Safety Reviewers so that
they will be able to perform safety reviews for road projects
undertaken by LTA.
Courses Conducted in 2010
The course conducted in March and October 2010 saw a total
of 39 participants from various disciplines in LTA, i.e. Design
Development (Road), Traffic Management, Safety, Rails, Road
Projects and Road Infrastructure Management. The course was
also attended by external consultants who are involved in road
works.
No rigid structure at the
central median
Figure 2: An example of clear zone concept discussed during the course
• Case studies
Participants were able to gain comprehensive understanding
of how road safety reviews were conducted through extensive
discussions on the case studies. It also helped prepare
participants for the hands-on activities, which are the site visits.
• Hands-on activities
The hands-on activities allow participants to apply what they
have learned into practice. During the exercise, participants
took up the role as road safety reviewers, undertook the safety
review and prepared the formal Safety Review Report.
Discussion
Before the actual site inspection, participants discussed about
the possible safety concerns they could identify based on the
drawing plans provided.
Figure 3: Course participants discussing on possible safety concerns
based on the drawing plans
Figure 1: Course participants and trainers
As the participants were from different disciplines and
background, they were able to gain great insights of various
road safety aspects through extensive interaction with each
other during the course.
Course Structure
The course was conducted in the form of:
• Lectures
There were a total of 12 topics taught during the course.
The lectures focused mainly on common road safety issues
associated with general alignment and cross section details,
junctions and interchanges, roadside hazard management and
temporary traffic control. Photos of good and poor examples
were shown to allow participants to have a better understanding
of the safety issues discussed
safety news
Actual Site Inspections
The site inspections were performed one during the day and
another in the eveing. It allows participants to identify potential
safety hazards that they could not pick up when reading the
drawings. For instance, participants could check whether the site
was adequately illuminated during the night inspection. It also
enabled participants to gauge if the recommendations proposed
to their findings were practical taking into consideration the
actual traffic conditions observed on site.
Figure 4: Course participants inspecting and observing the site to
identify major safety concerns
13
safety news
What the Participants said
“This course helps to strengthen
and reinforce my knowledge on
road safety. Now, I have a better
understanding of why certain safety
issues are critical which I don’t
understand in the past.”
Lim Hwee Min
Senior Engineering Officer from Traffic
Management, LTA
External participants
from Abu Dhabi
“The course is very relevant to my job scope back in Abu
Dhabi. I can now make comparisons between the practices
in Singapore and Abu Dhabi. Weighing the pros and cons
between the different practices, I can have a better judgment
of what is the better approach now.”
Mohamed Ahmed Al Alawi
Traffic Service Centre Engineer from Abu Dhabi Municipality
“As a safety engineer, I find this course particularly beneficial
to me. I would recommend this course to others, especially
those working in the road safety discipline.”
Manea Salem Mohamed Al-Seari
Road Safety Engineer from Abu Dhabi Municipality
“The course participants were
a good mix of consultants, site
staff, designers and contractors.
This serves as a good platform to
exchange valuable information.”
Kevin Nicholson
Traffic Consultant from Traffic Consult
“I like the hands-on activity where we get to go to site for
day and night inspection. I get to apply what I’ve learned into
practice.”
Ong Wee Sheng
Engineer from Ang & Ong Consultants
“The issues discussed allow me to have a deeper
understanding on road safety. I hope that the accidents on
our road will reduce significantly and I believe this can be
achieved.”
Tan Peng Chuan
Senior Engineer from AY Consultants
“The topics taught in this course were very informative and
constructive. It helps to increase my awareness on road safety.
I will be more careful in road design now so that the road
system can be safer for motorists and pedestrians to use.”
Angela Yeo
Principal Engineer from AY Consultants
14
“I have a clearer understanding on issues relating to Vehicle
Impact Guardrail (VIG) now which I was unsure of in the past.
I would recommend this course to others.”
Yeo Bee See
Higher Principal Engineering Officer from Design Development
(Road), LTA
“From this course, I learned about
what road safety review is all about.
One thing I like about the course
is being able to interact with other
participants who are from different
disciplines.”
Lukman Lim
Executive Project Engineer from
Marina Coastal Expressway
Subgroup, LTA
Conclusion
Staff and external consultants who attended the course and
obtained accreditation can conduct Road Safety Reviews for
all the road and rail projects undertaken by LTA. With more
upcoming road and rail projects, it is important to provide
training to raise the knowledge and understanding of road
safety engineering principles. This will ensure that the roads in
Singapore are safe to use.
Chua Saw Seng
Engineer, Road System Safety
Safety Division
2010
accident statistics
* Based on Singapore Workplace Safety and Health Act Requirements
15
E DITORIAL PAGE
Behaviour Based Safety (BBS) Training
As part of the BBS consultancy services,
consultant Tsinghua University conducted
four sessions of BBS training for selected
staff from LTA project teams and contractors
in January 2011.
It covered understanding of conducting
safety culture surveys, BBS observation
and intervention techniques, use of the
BBS software as well as setting targets to
improve safe behavior.
The training was well-received by the
participants with clear understanding of
implementing BBS. Knowledge gained by
the contractors will allow them to train their
staff and implement BBS on site.
Participants from last session of the BBS training
Road Safety Reviewer Accreditation Course (March 2011)
The next Road Safety Reviewer Accreditation Course is scheduled for late March 2011. The 4-day course is targeted for
interested parties who wish to become Accredited Road Safety Reviewer in Singapore. With the accreditation, they can
undertake safety reviews for LTA road projects. Participants will also get to learn more about road safety engineering principles
and understand more about the road safety situation in Singapore.
As the course requires participants to read drawing plans consisting mainly of traffic layout plans, site plans, longitudinal and
cross sectional details, it is recommended for people with at least 1 year experience in road or traffic engineering.
Interested LTA staff can apply through the Learning Roadmap via HR Links. External consultants interested in this course can
obtain a copy of the application form from LTA Academy.
Updated List of Approved Codes of
Practices
The WSH Council has recently approved an
updated list of Approved Codes of Practices
(ACOPs). These include the newly developed CP
on WSH Risk Management and CP for Working
Safely at Height.
Safety Phoa says…
All lifting machines, lifting
appliances and lifting gears
used on site must be suitable
for the task, used within their
rated safe load capacity and
must be in good working
conditions.
Please visit www.wshc.gov.sg to download the list
of revised ACOPs.
Interested parties can purchase the ACOPs from
SPRING’s appointed sales vendor.
Editorial Committee
Contributions or Feedback to:
Advisor
Corporate Safety Committee
Land Transport Authority
Safety Division
251 North Bridge Road, Singapore
179102
Tel: (65) 6332 6150 Fax: (65) 6332 6129
Email address: joanne_teo@lta.gov.sg
Safety News is also available online at
http://www.lta.gov.sg/projects/index_
proj_safety.htm
Editor
Joanne Teo Yu Jing
Circulation Officer
Zaidani Bte Ramli