Land Transport Authority of Singapore

Singapore, Singapore

Land Transport Authority of Singapore

Singapore, Singapore

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Meng Q.,National University of Singapore | Qu X.,National University of Singapore | Wang X.,National University of Singapore | Yuanita V.,Land Transport Authority of Singapore | Wong S.C.,Land Transport Authority of Singapore
Risk Analysis | Year: 2011

Urban road tunnels provide an increasingly cost-effective engineering solution, especially in compact cities like Singapore. For some urban road tunnels, tunnel characteristics such as tunnel configurations, geometries, provisions of tunnel electrical and mechanical systems, traffic volumes, etc. may vary from one section to another. These urban road tunnels that have characterized nonuniform parameters are referred to as nonhomogeneous urban road tunnels. In this study, a novel quantitative risk assessment (QRA) model is proposed for nonhomogeneous urban road tunnels because the existing QRA models for road tunnels are inapplicable to assess the risks in these road tunnels. This model uses a tunnel segmentation principle whereby a nonhomogeneous urban road tunnel is divided into various homogenous sections. Individual risk for road tunnel sections as well as the integrated risk indices for the entire road tunnel is defined. The article then proceeds to develop a new QRA model for each of the homogeneous sections. Compared to the existing QRA models for road tunnels, this section-based model incorporates one additional top event-toxic gases due to traffic congestion-and employs the Poisson regression method to estimate the vehicle accident frequencies of tunnel sections. This article further illustrates an aggregated QRA model for nonhomogeneous urban tunnels by integrating the section-based QRA models. Finally, a case study in Singapore is carried out. © 2010 Society for Risk Analysis.


Meng Q.,National University of Singapore | Qu X.,National University of Singapore | Yong K.T.,Land Transport Authority of Singapore | Wong Y.H.,Land Transport Authority of Singapore
Risk Analysis | Year: 2011

Road tunnels are vital infrastructures providing underground vehicular passageways for commuters and motorists. Various quantitative risk assessment (QRA) models have recently been developed and employed to evaluate the safety levels of road tunnels in terms of societal risk (as measured by theF/Ncurve). For a particular road tunnel, traffic volume and proportion of heavy goods vehicles (HGVs) are two adjustable parameters that may significantly affect the societal risk, and are thus very useful in implementing risk reduction solutions. To evaluate the impact the two contributing factors have on the risk, this article first presents an approach that employs a QRA model to generate societal risk for a series of possible combinations of the two factors. Some combinations may result inF/Ncurves that do not fulfill a predetermined safety target. This article thus proposes an "excess risk index" in order to quantify the road tunnel risk magnitudes that do not pass the safety target. The two-factor impact analysis can be illustrated by a contour chart based on the excess risk. Finally, the methodology has been applied to Singapore's KPE road tunnel and the results show that in terms of meeting the test safety target for societal risk, the traffic capacity of the tunnel should be no more than 1,200 vehs/h/lane, with a maximum proportion of 18% HGVs. © 2011 Society for Risk Analysis.


Qu X.,National University of Singapore | Meng Q.,National University of Singapore | Yuanita V.,Land Transport Authority of Singapore | Wong Y.H.,Land Transport Authority of Singapore
Expert Systems with Applications | Year: 2011

This paper presents an interesting approach to develop a quantitative risk assessment (QRA) software tool for road tunnels. It first introduces a QRA model for road tunnels, consisting of event trees, fault trees and consequence estimation models. The model is developed by taking into account the unique characteristics of Singapore road tunnels. The paper proceeds to describe design of the QRA software tool based on the QRA model by means of the object oriented design (OOD) method and eXtensible Markup Language (XML) technique. The XML files are used to store the numerous tree structures in the proposed model thus making the programming much more efficiently and effectively. The QRA software tool is robust and flexible such that users can easily add or modify the event trees, fault trees and the consequence estimation models. An application to Singapore road tunnels has been carried out to assess the robustness and effectiveness of the QRA software tool. © 2011 Elsevier Ltd. All rights reserved.


Xia B.,Shanghai Tong Hao Civil Engineering Consultant Co. | Wu Y.,Tongji University | Huang Z.,Land Transport Authority of Singapore
Frontiers of Structural and Civil Engineering | Year: 2012

In this paper, the co-rotational total Lagrangian forms of finite element formulations are derived to perform elasto-plastic analysis for plane steel frames that either experience increasing external loading at ambient temperature or constant external loading at elevated temperatures. Geometric nonlinearities and thermal-expansion effects are considered. A series of programs were developed based on these formulations. To verify the accuracy and efficiency of the nonlinear finite element programs, numerical benchmark tests were performed, and the results from these tests are in a good agreement with the literature. The effects of the nonlinear terms of the stiffness matrices on the computational results were investigated in detail. It was also demonstrated that the influence of geometric nonlinearities on the incremental steps of the finite element analysis for plane steel frames in the presence of fire is limited. © 2012 Higher Education Press and Springer-Verlag Berlin Heidelberg.


Sindhwani M.,235 Innovation Center Blk 2 | Xin Q.K.,Land Transport Authority of Singapore
17th ITS World Congress | Year: 2010

The Singapore Traffic Information Platform (TRIP) was developed in 2008 under a technical collaboration between the Land Transport Authority of Singapore (LTA) and Quantum Inventions (QI). The objective of TRIP is to provide consumers, enterprises and vendors with real-time traffic information to be directly used for dynamic route guidance applications. This will enhance the road networks and reduce road congestion as motorists are diverted away from traffic bottlenecks, increasing road safety and satisfaction amongst motorists from the enhanced experience, whilst addressing environmental concerns. In this project, a pilot trial was conducted to evaluate the reliability and effectiveness of processed traffic information. Reported data was correlated with data collected through real on-the-road drives to determine the similarity between the two. Simulations were also performed to estimate the effect of traffic-aware routing on overall travel time. Since its implementation, processed data from TRIP has powered numerous free as well as commercial, traffic-aware applications and solutions in Singapore. These include an RDS-TMC service, various mobile applications for traffic advisory, a Twitter feed, displays on web maps, and use in online and in-vehicle traffic-aware routing and navigation. In this paper, we share our experience in the development and deployment of TRIP, discussing the salient points of TRIP, in the use and processing of road traffic data collected by LTA to provide standardized machine-interoperable traffic information to in-vehicle systems over wireless media. We also share the results from the pilot trial drives and discuss the challenges and outcomes in providing services and applications to consumers.


Tan C.,Land Transport Authority of Singapore
17th ITS World Congress | Year: 2010

With a rapidly ageing population, Singapore will witness a threefold increase in the number of residents aged 65 years or older, i.e. from 300,000 now to 900,000 in 2030. By then, one out of every five residents will be a senior resident. With lower mobility, the elderly are a vulnerable group of users on the roads. Singapore recognises this fact and is constantly making its transportation infrastructures more elderly friendly to allow senior residents to live independently and to continue to engage actively in the society. Such an enabling environment must provide senior residents with safe unhindered access from homes to public amenities, communal and recreational facilities. On the other hand, there is a need to ensure that the needs of other road users, such as motorists, are not adversely affected when meeting the needs of the elderly. In this Green Man Plus project, the Land Transport Authority (LTA) uses technology to help the elderly cross the road more comfortably without adversely affecting the traffic flow. This paper presents the overview and experience of the implementation of the Green Man Plus system.


Cheong M.K.,Land Transport Authority of Singapore | Spearpoint M.J.,University of Canterbury | Fleischmann C.M.,University of Canterbury
Fire Technology | Year: 2010

Computational tools such as one-dimensional models or Computational Fluid Dynamics (CFD) have been used for the fire safety design of road tunnels. However, most of these analyses are performed using a specified fire source where the heat release rate (HRR) in the tunnel is fixed by the user and the influences of ventilation conditions and tunnel geometry are not considered. For a more realistic estimate, models need to incorporate these factors in their input. This paper discusses the use of a statistical approach previously developed by other researchers (Carvel and Beard, The handbook of tunnel fire safety. Thomas Telford Publishing, pp 184-197, 2005) and the use of a CFD approach to estimate the HRR in a road tunnel fire. As an application example, fire scenarios in which a light goods vehicle carrying wooden pallets are used to compare the estimation of the HRR using these two methods. © 2009 Springer Science+Business Media, LLC.


Cheong M.K.,Land Transport Authority of Singapore | Cheong W.O.,Land Transport Authority of Singapore | Leong K.W.,Land Transport Authority of Singapore | Lemaire A.D.,Efectis Nederland BV | And 2 more authors.
BHR Group - 15th International Symposium on Aerodynamics, Ventilation and Fire in Tunnels 2013 | Year: 2013

A fire in a tunnel can be a devastating and highly undesirable event if it is not addressed at the early stages of its development. This is particularly true for fires involving a heavy goods vehicle carrying combustibles with high calorific content. Heat, soot and toxic combustibles can be produced very rapidly and therefore significantly increase the difficulty for escape, rescue and fire-fighting activities. A series of large-scale fire tests for road tunnel application was conducted at the TST tunnel facility in Spain in March 2012. The aims of this fire tests programme were to investigate the magnitude of the heat release rate generated with and without a low-pressure deluge fire suppression system; the effects of other measures in the presence of a fire suppression system such as reducing the longitudinal flow velocity; and to acquire information on the appropriate design parameters (e.g. nozzle type, discharge density and activation time) to adopt, based on the most probable fuel load used in the Singapore road tunnels. In order to ensure repeatability, simulated heavy goods vehicles consisting of 228 pallets with 48 plastic pallets (20% by volume) and 180 wooden pallets (80% by volume) were used in all fire tests. A longitudinal air velocity of 3 m/s was applied in the tunnel fire tests. The test results confirm that a substantial reduction of fire heat release rate can he obtained using a low-pressure deluge fire suppression system, as long as timely activation of the water is provided. The provision of such experimental data thus addresses the current dearth of knowledge on the actual effects of low-pressure deluge systems on the heat release rates from HGVs in tunnel fires. © BHR Group 2013.


Tarada F.,Mosen Ltd. | Noordijk L.M.,Efectis Nederland BV | Cheong M.K.,Land Transport Authority of Singapore | Cheong W.O.,Land Transport Authority of Singapore | Leong K.W.,Land Transport Authority of Singapore
BHR Group - 15th International Symposium on Aerodynamics, Ventilation and Fire in Tunnels 2013 | Year: 2013

There has been substantial interest in the use of fire suppression systems to reduce risks to tunnel structures, improve life safety and to enhance road network integrity. A key factor in delivering these benefits is the reduction in heat release rates from fires through the deployment of fire suppression, as reported in our companion paper to this Symposium. However, it is this paper's contention that fire suppression provides another dimension in the delivery of risk-reduction benefits: namely, that a significant proportion of the residual fire heat release rate is absorbed through a benign process of heating and evaporation of water, rather than through convection or radiation. Measurements were undertaken during the course of medium-scale fire tests using stacks of wooden (80%) and plastic (20%) pallets. This combination of combustibles was considered to be representative of HGV loads in Singapore. The fire heat release rates were estimated using the oxygen depletion calorimetry method, based on sensors installed within a smoke exhaust hood. A low-pressure deluge system with discharge density in the range of 8-12mm/min was used in the tests. Results from the medium-scale fire tests and also from full-scale fire tests suggest that the convective heat transfer rate is generally no more than 50% of the suppressed fire heat release rate. This finding may allow a reduction in the capacity of longitudinal ventilation systems for smoke control. © BHR Group 2013.


Lemaire A.D.,Efectis Nederland BV | Noordijk L.M.,Efectis Nederland BV | Vermeer M.,Efectis Nederland BV | Cheong M.K.,Land Transport Authority of Singapore | Cheong W.O.,Land Transport Authority of Singapore
BHR Group - 15th International Symposium on Aerodynamics, Ventilation and Fire in Tunnels 2013 | Year: 2013

Tunnel fires pose a serious threat to the integrity of the tunnel structure. Temperatures over 1200°C can be reached within minutes and therefore the tunnel lining is normally assessed in fire tests, exposed to high temperature fire curves like the RWS or HCM fire curve. In order to assess the effect of deluge systems on life safety and property protection, the Land Transport Authority (LTA) of Singapore commissioned Efectis contract ER376 "Fire test programme for road tunnels with fire suppression system", which included a series of large scale fire tests with a low pressure deluge sprinkler system, conducted at the TST tunnel facility in Spain in March 2012. In order to ensure repeatability, simulated heavy goods vehicles consisting of 228 wooden and plastic pallets were used in all fire tests. Longitudinal air velocities between 1 m/s and 3 m/s were applied in the tunnel fire tests. In this paper the effect of the deluge system on the thermal load on the tunnel structure is addressed. The fire test results are transferred into a Time-Temperature curve (fire curve) representative for the thermal load on the tunnel structure caused by a rigid heavy goods vehicle fire in a tunnel equipped with a deluge fire suppression system, which is activated in time. The fire curve can be used to assess the structural damage due to concrete spalling of an unprotected tunnel structure in a (mobile) furnace fire test. The fire test results with respect to spalling combined with the fire curve can also be used for structural analyses of the mechanical behaviour of the tunnel structure in case of fire. © BHR Group 2013.

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