Sustainable Solutions for Railways and Transportation Engineering

This paper presents an optimization algorithm for finding the railway track longitudinal profile from the inertial response of a train bogie. The track profile is that which creates a numerical response from a numerical train-track interaction model that best fits the measured response. An Irish Rail InterCity train was instrumented to capture in-service vehicle responses to validate the proposed algorithm. Several train passes in the Dublin-Belfast service in Ireland over a period of 4 weeks are used. Vertical acceleration and angular velocity at the train bogie were measured. The real longitudinal profile of a section of this line was surveyed by traditional means, for reference. The vehicle properties were available from a calibration study. The track profile is estimated using the proposed method which matches quite well with the surveyed profile. The reproducibility of the method is assessed.

Resilient modulus (M_r) is a representative property for characterizing unbound granular materials and subgrade soils. It exhibits the elastic behavior as well as the load-bearing ability of pavement materials under cyclic traffic loads. This paper investigates the influence of using recycled plastic Polyethylene Terephthalate (PET) as a soil reinforcement material on the M_r of a clayey soil; ordinary soil in the delta region in Egypt. A comprehensive laboratory testing was conducted at Mansoura University Highway and Airport Engineering Laboratory (H&AE-LAB). The conducted testing includes standard engineering tests and repeated-loading triaxial tests (RLTT). Laboratory specimens were prepared at four different percentages of the recycled PET (0%, 0.2%, 0.6%, and 1.0%). RLTT results shows that the M_r of 0.6% PET-reinforced specimens increases by 58% compared to the M_r of the control specimen (0% PET). However, the M_r of the reinforced soil is found to decrease with the increase of PET percentage. Moreover, the universal M_r model exhibits excellent M_r predictions for the control and the PET-reinforced clay soil. Economically, the initial cost for constructing a 10-km road segment decreases by 8% using the 0.6% PET-reinforced Subgrade compared to the control Subgrade. Finally, damage analysis using the KENLAYER software is used to manifest the enhancement of pavement performance by reinforcing the Subgrade with PET.

Soil stabilization is the process of improving the shear strength parameters of soil and thus increasing its bearing capacity in road construction. It is required when the soil available for construction is not suitable to carry structural load. Generally, soils exhibit undesirable engineering properties unless they are treated to enhance their physical properties. Stabilization can increase the shear strength of a soil and control its shrink-swell properties, thereby improving the load bearing capacity of a sub-grade to support pavement and its foundations. Soil stabilization is used to reduce permeability and compressibility of the soil mass in earth structures and to increase its shear strength. Mixing additives into the reaction mechanism, positively affecting its strength, improving and maintaining the soil moisture content, achieve stabilization. Therefore, these soil stabilization processes are suggested for most construction systems and can be accomplished by several methods. All these methods fall into two broad categories, namely mechanical stabilization and chemical stabilization. Mechanical Stabilization is the process of improving the properties of the soil by changing its gradation; chemical stabilization is the process of adding a physico-synthetic substance to the soil which reacts with the clay particles to fill the voids so that less water is needed to maintain a stable mix and, finally, a stable framework.

Several aspects must be considered when evaluating the sustainability of a railway, such as the use of mineral aggregates in ballasted tracks. To this day, most of the cargo and passenger railways around the world are built on granular layers of rocky material, which is called ballast. It has the structural function of absorbing and dissipating the vertical stresses resulting from train traffic, at the same time as it allows the quick drainage of rain water and facilitates the correction of geometrical defects of the track’s alignment. Nonetheless, ballast grains lose mass due to abrasion, which results in contamination of the layer and differential settlings of the track. Problems also emerge when the railway is constructed without sub-ballast, a blocking and filtering layer located between ballast and subgrade. In developing countries such as Brazil there is still shortage of efficient technology for ballast maintenance, like what is employed in Europe and North America. Likewise, it is common to rebuild or rehabilitate old lines that endure heavy cargo traffic without executing the sub-ballast layer. Considering that ballast is a non-renewable natural material it is compelling that such practices be reviewed and replaced by more sustainable techniques. At the same time, it becomes essential that rocks with adequate properties are used in the construction and maintenance of the railway ballast, so that its life span is the longest possible. The objective of this work is to provoke reflection regarding the rational use of mineral non-renewable resources in the construction and maintenance of rail tracks. A review was made on the desirable properties of rocks to be used as railway ballast. Simultaneously, studies are presented that evaluated the consequences of the absence of sub-ballast in the performance of a railway, as well as different techniques that are used to avoid the interlocking of ballast particles into the subgrade. Finally, recommendations are made to constructors and keepers of rail tracks in developing countries, reinforcing the technical and economic advantages of some already established solutions.

Severity of climate condition is becoming more frequent, therefore it much important to be very clear about the influence of climate on road users daily travelling pattern. Climate change has much effect on the aspects of transportation systems such as. Climate change is three dimensional which are exposed, sensitive and low adaptive capacity to traffic highway. Although these dimensions of climate impact on traffic highway are measurable and predominant, they need potential adapters to monitor and support the adaptive response, potential persisted to monitor population trend and high latent risk to monitor the environment. This includes traffic demand, traffic safety and traffic operation relationships. Furthermore, research as established that severe climate change such as winter storm brings about 25 times the normality of vehicular crashes, this is however, much higher than the risk brought by the road users behavior. The risk of drivers involved in a vehicular crashes becomes more intense as a result of extreme weather conditions. Thus, there is a need for the transportation related authorities to manage and restrict the use of highways during extreme condition in order to vehicle operation cost and other related cost. Nevertheless, the first step by transportation agencies to manage transportation systems to minimize the weather impact is to quantify its impact on traffic on highways.

Thus, this paper presents a review of the impact of climate condition on traffic demand, traffic safety and traffic operation relationships. Using a case study area of Eastern Cape Province in South Africa, accident reports were collected from secondary sources and analyzed. Overall, a relationship is drawn on the impact of climate condition and travel fatality. Furthermore, traffic regulation recommendations based on the impact of climate conditions will be drawn.

Road user behavior is one of the most critical components of traffic system, this is because it is unpredictable in nature. The variation in the behavioral responses of the road users has significantly contributed to the increase in traffic fatality rate. Consequently, the need for traffic control measures arises. Traffic control system such as traffic signals, traffic signs and road markings, on a road network tends to considerably reduce the number of conflicts and minimize road user’s mistakes. However, the mortality rate on road accidents is on the increasing trend globally. Focusing on road markings as a traffic control system, the conducted study investigates the reaction behavior of drivers to road marking. Using random sampling methods, cross-border drivers between Main South-Road Lesotho and N8 Road, South Africa were interviewed on their experiences when driving on marked and unmarked roads. The questionnaire includes sections on driver personal experience, driver’s reactions to road markings and the necessity for road marking and other traffic controls. Results show that approximately 67.7% of the drivers agree that their psychological state is influenced by road markings. Furthermore, using chi-square statistical analysis, results establish that the gender, age and educational background characteristics of drivers and their psychological responses to road marking are dependent on each other. In conclusion, emphasis on the necessity of road marking in reducing traffic fatality rate and the psychological effect of the unavailability of road marking on driver’s behavior in most developing countries is presented.

The resilient behavior of asphalt stabilized subgrade soil in terms of changes in the deformation and shear failure under repeated loading was investigated in this work. Asphalt stabilized soil specimens of two sizes (100 mm diameter and 70 mm height) and (152 mm diameter with 127 mm height) have been prepared in the laboratory and compacted to its maximum dry density at optimum fluid requirement (water + liquid asphalt) and at 0.5% of fluid above and below the optimum. Specimens have been subjected to curing, then tested for deformation and resilient modulus under repeated shear stresses. The deformation was captured along the load repetition process with the aid of linear variable differential transformer (LVDT) under controlled stress and environmental conditions in the pneumatic repeated load system (PRLS) until failure. The large size specimens were tested under single punching shear stress, while small size specimens were tested under double punching shear stress after eight days of curing. The resilient deformation data of the two testing techniques under single and double punching shear stress was analyzed and compared. It was observed that the Double punching shear exhibit higher resilient strain than that of single punch shear in a range of (22, 8, and 24)% for (16.5, 16, and 15.5)% of fluid content respectively. The resilient modulus decreases after 1200 and 1800 load repetitions by (48, 47, 61, and 32)% and (50, 48, 63, and 34)% for (untreated soil, 15.5, 16, and 16.5)% fluid content respectively as compared to that after one load repetition under single punch shear stress. It was concluded that asphalt stabilization exhibit positive impact on resilient modulus. It increases by a range of three and seven folds under single and double punch shear stress after one load repetition by the addition of asphalt. Higher asphalt content exhibit reduction of Mr. Significant reduction in total and resilient strain could be detected after liquid asphalt was implemented in the subgrade soil.

The time headway is important parameter in traffic flow theory and broadly applied in different branches in transportation engineering. In this research the one of the major arterial street in Baghdad city is Palestine arterial street that have been selected as a case study to investigate the distribution of time headway under heavy flow conditions. Collected field data for tow links; Link (1) from Al-Mawal intersection to Bab AlMutham intersection 1.03 km length and link (2) from Zayona intersection to Mayslone intersection is obtained at two different time periods to conform the variation of time headway under congestion periods. The variation in time headway for Link (1) is reduced and more constant state is obtained due heavy flow conditions at congestion peak periods. The situation is not the same on Link (2), the fluctuation in time headway is still observed at higher flow rate. This demonstrated the effect of land use characteristics on time headway distribution and vehicle arrivals. Both Shape for the distribution of probability density function is skewed to the right and the peak rises for link (1) and its higher than for link (2). This illustrated that the peak value for probability density function is higher on link (1) which implies high flow rate at congestion periods. The Logostic probability distribution function is used to probably describe the time headway at congested Palestine arterial street for link (1) and (2). The fitted field data of time headway for different range of scale parameter from 1.5 to 0.85 are obtained. Goodness of fit using Chi Square non- parametric test is applied in this research to explore how the theoretical Logostic distribution fits the empirical data for time headway distribution.

In railway industry, high strength concrete has been adopted for track slabs and railway sleepers for more than half a century. Prestressed concrete sleepers (or railroad ties) are designed usually using high strength concrete (>55 MPa) in order to carry and transfer the wheel loads from the rails to the ground and to maintain rail gauge for safe train travels. In general, the railway sleepers are installed as the crosstie beam support in ballasted railway tracks. Statistically, they are subjected to impact loading conditions induced by train operations over wheel or rail irregularities, such as flat wheels, dipped rails, crossing transfers, rail squats, corrugation, etc. These defects can be commonly found during the operational stage of life cycle. The magnitude of the shock load depends on various factors such as axle load, types of wheel/rail imperfections, speeds of vehicle, track stiffness, etc. This paper demonstrates the investigations into the dynamic responses of in-situ prestressed concrete sleepers using high strength materials, particularly under a variety of impact loads. The nonlinear finite element model of full-scale prestressed concrete sleeper with the realistic support condition has been developed using a finite element package, STRAND7. It has been verified by the experiments carried out using the high capacity drop-weight impact machine and experimental modal testing. The experimental results exhibited very good correlation with numerical simulations. In this paper, the numerical studies are extended to evaluate the dynamic behaviors of high strength concrete sleepers modified by crumb rubbers to increase material damping coefficients. The outcome of this study can potentially lead to the utilization and practical design guideline of high strength concrete engineered by crumb rubber from wasted tires and plastics for prestressed concrete sleepers.

Rail squats and studs are typically classified as the propagation of any cracks that have grown longitudinally through the subsurface. Some of the cracks could propagate to the bottom of rails transversely, which have branched from the initial longitudinal cracks with a depression of rail surface. The rail defects are commonly referred to as ‘squats’ when they were initiated from damage layer caused by rolling contact fatigue, and as ‘studs’ when they were associated with white etching layer caused by the transform from pearlitic steel due to friction heat generated by wheel sliding or excessive traction. Such above-mentioned rail defects have been often observed in railway tracks catered for either light passenger or heavy freight traffics and for low, medium or high speed trains all over the world for over 60 years except some places such as sharp curves where large wear takes place under severe friction between wheel flange and rail gauge face. It becomes a much-more significant issue when the crack grows and sometimes flakes off the rail (by itself or by insufficient rail grinding), resulting in a rail surface irregularity. Such rail surface defect induces wheel/rail impact and large amplitude vibration of track structure and poor ride quality. In Australia, Europe and Japan, rail squats/studs have occasionally turned into broken rails. The root cause and preventive solution to this defect are still under investigation from the fracture mechanics and material sciences point of view. Some patterns of squat/stud development related to both of curve and tangent track geometries have been observed, and squat growth has also been monitored for individual squats using ultrasonic mapping techniques. This paper highlights peridynamic modeling of squat/stud distribution and its growth. Squat/stud growth has been measured in the field using the ultrasonic measurement device on a grid applied to the rail surface. The depths of crack paths at each grid node form a three dimensional contour of rail squat crack. The crack propagation of squats/studs is modelled using peridynamics. The modeling and field data is compared to evaluate the effectiveness of peridynamics in modelling rail squats.

In construction industry, state-of-the-art experimental trials such as plastic road by Scottish and rubber road in Malaysia have shown potential value in the utilization of locally available wastes in engineering projects. Malaysia, the second largest global producers of palm oil and related products, estimates millions of tons of biomass by-product annually. Oil Palm Shell (OPS) is one amongst the biomass thus produced. OPS is well noted in literatures for its low specific gravity and better strength/stiffness, though not in absolute comparison to aggregates. Thus, an eco-composite with OPS supplementing conventional sub-base material hypothetically is a promising alternative, facilitating productive utilization of OPS – an agricultural waste, reducing the self-weight of the sub-base, and soil reinforcement leading to improved strength. The main aim of this paper is to study the influence of OPS content on the compaction behavior and strength improvement of soil-OPS composites for its application as sub-base material in rural roads. Basic properties of the OPS samples and three soil samples locally procured – kaolin, medium sand and clayey sand, were evaluated in laboratory. The performance of soil-OPS composite in terms of their compaction and California bearing ratios is evaluated and discussed in this paper. In conclusion, the OPS was observed to have significant influence on the compaction characteristics and strength (CBR). In brief, the porous surface texture of OPS is most likely the key parameter controlling the compaction parameters, while contributions from the tensile strength of individual OPS samples potentially has a significant influence on the strength (CBR) improvements observed in this pilot study.

Growing world population and increasing urbanization continues to stress cities and negatively impact people mobility. Morning and evening peaks of traffic congestion threaten to merge into a continuous never-ending congestion. Two main causes create this problem: an over-concentration of working places in city centers and a dis-proportionately large share of private cars in the traffic. Ownership and use of private vehicles are naturally encouraged by a typical layout of modern cities with living areas in suburbs which are dissolving passenger flows and making public transport ineffective there. A classical Park & Ride system is designed to attract and eliminate private cars coming from suburbs and transfer passengers to public transport for further travel towards the city center. However, most of these systems have limitations - if the parking space is large enough it requires a lot of real estate and it is difficult to access and exit, and if it is small enough to be convenient it does not have a sufficient effect. We present several innovative multifunctional road junctions which can act both as intersections of continuous flow and also utilize their occupied plot of land at the same time therefore becoming natural Park & Ride systems. All presented junctions have only two levels but traffic flows do not intersect. Their capacity is not limited by design. They enable non-interrupted flows in all directions as well as a possibility to make a U-turn. Most importantly, the junctions enable an easy access to a free area inside them. Thus the area can be utilized either for parking spaces, logistics or business centers, and public transport hubs with easy transfer capabilities between different modes of transport. Depending on the design one such junction can easily accommodate 20 thousand vehicles and create as many new working places. Placing the junctions on major intersections would both decentralize a city and create an effective infrastructure for multi-modal travel. Additionally, ITS can be easily employed to manage traffic flows and concentrate passengers creating a smart solution for city mobility. The multi-modal transportation system does not require any major changes of the road infrastructure inside a city and it is therefore a good choice both for a new or an old growing city.

Layered cushion material is widely used in concrete-faced rockfill dams and embankment of highway. The deformation of the cushion material is dominant to the safety of the concrete face or pavement. If the total or differential deformation of cushion material is too large, cracks may develop in concrete face or pavement, and even more destruction may happen to the whole structure. In cold area, the excessive deformation of cushion material may happen because of repeated frost heave and thaw collapse during freeze-thaw cycles. For better understanding on this excessive deformation and optimum design for cushion material, series laboratory tests are carried out on four types of samples with different layered structure. A self-developed one-dimensional freeze-thaw device is used to monitor the deformation of specimen during freeze-thaw cycles. Test results show that it’s not always frost heave or thaw collapse during freeze-thaw cycles. All specimen show collapse during frost and heave while thaw in the first freeze-thaw cycle. Comparisons are conducted on the four types of layered samples. Comparison results show that the sample with a “loose top and dense bottom” structure deforms relatively small out of four types of layered samples. It also shows that the deformation of frost heave and thaw collapse tends to a stable value along with the freeze-thaw cycles increasing.

Soil pumping phenomena comprise a wide issue in traditional railway structures. A newly built railway structure from the top down contains rails, slippers, ballasts and soil layer foundation. Currently about 85% of the railway structure is constructed traditionally in Taiwan as mentioned. With the infiltration of rainfall or groundwater, the soil foundation will become saturated. After repeated loading from passing, trains the soil will become even more saturated and squeezed into the voids inside the sub-ballasts or ballasts. The pumping effect is then initiated and the pumping paths start to scurry. The repeatedly force transfers through ballast to the saturated foundation, may create vacuum to draw phenomenon, called pump effect or mud pumping. It could lead to serious train derailment capsized. Present mud pumping detection method has to be performed during the non-operating time at night by visual. However, this approach may have omissions and shortcomings perspective concerns, and slow to find disasters during the rainy season. According to previous studied result, the pumped mud is characteristic of being quasi-liquefied, denser, and with exceed pore-water pressure. The loading from trains cause dynamic force to rise the pore-water pressure. Adopting the feature, a tubing-floater device is proposed to install on the interface between ballasts and soil layer foundation. No matter the ballast sinks or mud pumping up, the floater will be raised due to the pressure generated in the tube. The laboratorial experiment has been performed to prove the feasibility of the idea herein.