Yusuf Mehta

Effectiveness of Motorcycle Training and Licensing

Motorcycle crash fatalities in the United States have been increasing since 1997, when the total number of fatalities reached a record low. Motorcycle training programs were enacted before this rise, and many studies have aimed to show their effectiveness. The objective of this study is to review and synthesize the results of existing research on the effectiveness of motorcycle education courses and different licensing procedures. The effectiveness of programs is examined through the effect training has on accident rates, violation rates, and personal protective equipment use found through past research. Research to date has not consistently supported the notion that training is either effective or ineffective. Some studies have demonstrated that accident and traffic violation rates are lower for trained riders than for untrained riders, whereas others have demonstrated that they are higher for trained riders. Training increases the use of personal protective equipment among motorcyclists. Motorcycle licensing procedures have been shown to have different effects on accident rates. Lower accident rates have been observed in areas with stricter regulations for obtaining a license. The studies vary greatly in both the methods used for comparison and the rigor of their evaluation methodology. No standards for evaluation exist. The findings of these previous studies may be more a reflection of the methods used to evaluate motorcycle training than the effectiveness of training itself.

A COMPARISON OF THE MARSHALL AND SUPERPAVE DESIGN PROCEDURE FOR MATERIALS SOURCED IN INDIA

Developing countries are striving for the development of infrastructure facilities including transportation systems. India has a national highway with a length over 52,000 km. A further 14,000 km length of express highway is currently being built under the golden quadrangle and North–South and East–West corridor projects. These projects have large scope for adopting superpave technology. The strategic highway research program (SHRP) conducted a

Evaluation of Percent-within-limits Construction Specification Parameters

50 million research effort from 1987 to 1993 to develop a new concept for the design of bituminous mixes referred to as superior performing asphalt pavements (superpave). Superpave mixes have been widely used by the developed countries for the last few years but the developing countries are still working with the conventional mixes i.e. marshall mixes. Flexible pavements, with bituminous surfacing as a wearing course, are widely used in India. The objective of this study was to compare the design of asphaltic concrete by the superpave and marshall methods of mix design. A detailed laboratory study was carried out using aggregate from the Delhi region and bitumen from the Mathura refinery. From the analysis of design of asphaltic concrete, it was observed that superpave mixes fulfill all the criteria for easy and good construction at lesser binder content than the marshall mixes. Apart from superpave mix design, the effect of angle of gyration, number of gyrations on mix properties like density, stability, indirect tensile strength were also determined. Results revealed that percentage theoretical maximum density increases with the increase in number of gyrations. At any level of gyration, theoretical maximum density percentage increases with increase in gyratory angle. Further, it was observed that indirect tensile strength decreases with increase in angle of gyrations. Comparing both the design methods, it was observed that marshall compactor is unable to answer the rutting resistance of the designed mixture. The marshall compaction effort in the field laboratory corresponded to an air void content of slightly less than six percent, and the mixture appeared to stabilize under traffic at an air void content between three and four percent. In contrast, superpave gyratory compactor is capable of achieving air void contents much lower than achieved by mechanical marshall hammer compaction. This prevents additional compaction under traffic, which could result in rutting in the wheel paths. Hence, marshall mix design should be replaced by superpave mix design for Indian national highways/express highways, which compact the specimens in the same manner as compacted under actual pavement climate and loading conditions.

Exploring pay factors based on hot mix asphalt performance using quality-related specification software

Various state agencies, including the Florida Department of Transportation are rapidly moving towards a more practical percent-within-limit (PWL) specification. The current specification is based on unknown standard deviation because the range of variability is high and difficult to estimate. The parameters of PWL specifications, the acceptable quality level (AQL) and the rejectable quality level (RQL), which are selected based on engineering judgment, could lead to buyer and seller risk level greater than the values recommended by American Association of State Highway Transportation Officials (AASHTO). The purpose of this paper is to provide guidelines to determine AQL, RQL and appropriate sampling frequency using operation characteristic (OC) curves based on known standard deviation to achieve the recommended risk levels. This was demonstrated by selecting two parameters (a) asphalt content and (b) the percent passing 2.36 mm sieve, of ten Superpave mixtures. The study showed that an excessive sampling frequency of ten per lot was required to achieve the AASHTO recommended buyers risk of 5%. In addition, a framework was developed to evaluate the sampling plan and its associated the risk level based on the construction and material variability observed in the field.

Load Transfer Efficiency of Rigid Airfield Pavement: Relationship to Design Thickness and Temperature Curling

A parametric study was conducted that established quality-related specification relationships for hot mix asphalt (HMA) design and construction. Factorial analysis identified the significance of several factors, developed regression models, and explored how variations in specifications led to additional incentive or disincentive pay. The equations may allow contractors and transportation agencies to plan as-built or job mix formula requirements based on incentive/disincentive risk. Approximately 92% of the surface lift rutting and 63% of the binder lift rutting data indicate no difference in pay as a result of discrepancy between predictive model and quality-related specification software-measured pay factors. Observations and recommendations for implementation and further study are presented in this paper.

Impact of dynamic loading on backcalculated stiffness of rigid airfield pavements

FAA uses a mechanistic design procedure, FAA Rigid and Flexible Iterative Elastic Layer Design (FAARFIELD), for the design of rigid airport pavements. FAARFIELD does not consider curling stresses in determining the portland cement concrete (PCC) layer thickness and assumes constant stress-based load transfer efficiency [LTE (S)] of 0.25 at the joints. Recently completed studies have shown that LTE (S) values under moving aircraft loads can be significantly higher than 0.25. In addition, the curling stresses, induced because of the temperature differentials at the top and bottom of the PCC slab, can affect the load transfer efficiency at the joint. Higher curling stresses can lead to higher combined stresses (loading plus curling) in pavements. The objective of this study is to analyze the effect of load transfer efficiency and loading intensity on PCC design thickness and the effect of PCC temperature gradient on LTE (S) and critical edge stresses. The results indicate that for a slab that shows no curling, an increase in LTE (S) value by 0.10 would reduce the PCC design thickness by 1.3 in. (33 mm) under FAA design procedures. In addition, when the top of the slab has a higher temperature than does the bottom of the slab, higher stresses at the joint and higher LTE (S) are observed. The variations in temperature gradient induce curling stresses in the slab and affect the LTE (S) at the joints.

Mechanical Responses and Viscoelastic Properties of Asphalt Mixtures Under Heavy Static and Dynamic Aircraft Loads

The objective of this paper was to evaluate the deterioration of Portland Cement Concrete (PCC) slabs throughout trafficking. A full-scale accelerated pavement testing at the National Airport Pavement Test Facility (NAPTF) was conducted on Construction Cycle 6 (CC6) on rigid pavements with low, medium and high flexural strengths on both a concrete and asphalt stabilised base. Heavy Weight Deflectometer (HWD) testing was conducted on the test sections to backcalculate the stiffness of the layers. The majority of PCC deterioration occurred roughly within the first 1500–2000 passes of trafficking. On average, the MRS-1 (low flexural strength) PCC elastic modulus was found to decrease by 20%, from 5.0–.4 × 106 (34.5–37.2 GPa) to 4.0–4.3 × 106 psi (27.6–29.7 GPa), whereas the PCC elastic modulus of MRS-2 and MRS-3 was found to decrease by 17% and 22%, respectively. However, neither the MRS-2 nor MRS-3 elastic modulus was found to drop below 5.0 × 106 psi (34.5 GPa) after 15,000 passes.

Rating Roads for Motorcyclist Safety: Development of a Motorcycle Road Assessment Program

The introduction of larger aircraft on flexible airfield pavements has led to a need for asphalt mixtures capable of sustaining such heavy loads. This laboratory and analytical study investigated the mechanical responses of a number of modified asphalt mixtures to identify their potential for use in airfield aprons and taxiways that were subjected to heavy, static, or slow-moving aircraft loads. The airfield flexible pavement section constructed at the FAAs National Airport Pavement Test Facility Construction Cycle 1 was modeled by using the three-dimensional finite element analysis software ABAQUS. Laboratory-compacted specimens of each modified asphalt mixture were tested by using AASHTO standards to determine volumetric properties and mechanical responses. The effects of static and dynamic aircraft loading were evaluated in ABAQUS with the material properties of the mixtures determined in the laboratory. On the basis of the findings of this study, it appears that several mixtures more commonly used in highway pavements, including modified mixtures, warm-mix asphalt, and reclaimed asphalt pavement, perform similarly to or even outperformed the FAA standard asphalt mixture. The results of this initial study support the idea that an opportunity exists for airports to implement emerging asphalt paving materials without compromising the pavement design life.

The importance of mineral filler on construction specifications

Motorcycles are vastly different from other vehicles on the road: they are highly unstable and provide little protection to users. Because of motorcycle instability, variations in road surfaces and geometry may be more hazardous to motorcyclists than to other road users. Road safety ratings for the entire vehicle fleet, primarily cars, have been applied to roadways in Europe, the United States, and Australia. However, these primarily car-oriented systems have limited value for motorcyclists. This study develops a unique road safety rating system designed for motorcyclists. On the basis of normalized motorcycle crash rates, roads were classified into five safety rating categories, ranging from low risk to severe risk. The new methodology for rating roads was applied to 16 roads in New Jersey, covering 1,099.5 mi (1,769.5 km) of road. Roadways were mapped to create a visual representation of the distribution of safety hazards on the analyzed roads. Of these roads, 19% posed a severe risk to motorcyclists. The majority of the roads mapped (27%) had a medium risk for motorcycles. The statewide crash risk mapping was supplemented by an in-depth site investigation of an area known to be particularly hazardous to motorcyclists, to develop a better understanding of potentially dangerous roadway conditions.

A Study to Determine the Impact of Cracking on Load Transfer Efficiency of Rigid Airfield Pavements

Studies have been conducted to date to demonstrate how the dust content in hot-mix-asphalt (HMA) should be accounted for in construction specifications. It may be detrimental to pavement performance if a high change in the dust content from the actual target value is not captured during HMA production. A study was conducted to determine whether the present composite pay factor (CPF) in Florida reflects the laboratory predicted loss in cracking performance. Resilient modulus, creep and strength tests, along with the University of Florida fracture mechanics model were used on 18 Superpave mixtures. Based on the analysis conducted, it was found that the current CPF in Florida did not reflect the expected loss in performance. The results showed that a 2% increase in dust can be at least as or more detrimental than 0.7% reduction in the asphalt content. However, this was not reflected in the weighted factor assigned to dust in the CPF equation. In this research, a framework to identify performance-based acceptance procedures was also presented. Ideally, this framework can be used to develop or modify construction specifications so that the expected performance of HMA can be assessed accordingly.