Kunnawee Kanitpong

Hydraulic Conductivity (Permeability) of Laboratory-Compacted Asphalt Mixtures

A flexible-wall permeameter was used to study the hydraulic conductivity (also referred to as “permeability”) of asphalt mixtures commonly used in Wisconsin. Effects of saturation, hydraulic gradient, and sidewall leakage were studied to determine an appropriate testing procedure. The test procedure was then used to study how mixture design variables affect hydraulic conductivity. Four aggregate gradations were tested to develop relationships between hydraulic conductivity and volumetric properties. Two mixtures were also compacted to different heights (ranging from 37.5 mm to 110.0 mm) to evaluate how lift thickness affects hydraulic conductivity. Results of the tests indicate that back-pressure saturation can be used to ensure that specimens are saturated and that the saturated hydraulic conductivity is measured. Sidewall leakage was eliminated by using bentonite clay as a sealing agent. The hydraulic gradient was selected on the basis of a parametric experiment showing how the gradient affects hydraulic conductivity. Tests on the various mixtures showed that a power-law relationship exists between air voids content and hydraulic conductivity, but the hydraulic conductivity also depends on the gradation. Lift thickness also appears to be important, with lower hydraulic conductivity obtained from greater lift thickness at a given air void content. The results show that hydraulic conductivity cannot be controlled only by limiting air voids and that a hydraulic conductivity test is necessary for a mixture design that includes hydraulic conductivity as a criterion.

Evaluation of HMA Moisture Damage in Wisconsin as it Relates to Pavement Performance

The Wisconsin Department of Transportation (WisDOT) has been using the tensile strength ratio (TSR) test (ASTM D-4867) to predict the potential susceptibility of asphalt mixture to moisture damage and other associated pavement deterioration. The objectives of this paper are to evaluate the relationship between the performance of asphalt pavements in the field and the TSR values measured in laboratory on the original asphalt mixtures used in constructing pavements, and to evaluate the effect of anti-stripping additives on field performance. To assess the moisture damage problem in the field, 21 existing WisDOT pavement sections that were built prior to the adoption of the TSR parameter as a requirement, were selected to cover a wide range of locations and aggregate sources. The TSR and the pavement performance data (pavement distress index or PDI) for these projects were collected from the WisDOT pavement management database. The results indicated no relationship between TSR and field pavement performance as measured by the PDI, and no relationship between TSR and specific pavement distresses that are related to moisture damage (surface raveling and rutting). To evaluate the effect of using anti-stripping additive, a database study and a laboratory study were conducted. The database showed an effect of using anti-stripping additives on the pavement performance and also on the specific pavement distresses that are related to moisture damage. In laboratory testing, anti-stripping additive was not found to change the rheological properties of asphalt binders, nor to improve the rutting and fatigue related properties of asphalt binder as measured by the dynamic shear rheometer (DSR). However, they were found to increase the adhesion of asphalt binder to selected mineral aggregate surfaces, especially when the binder bond is exposed to water. These findings lead to believe that better field performance is achieved by better adhesion between binders and aggregates. The findings also point out that although the TSR testing is sensitive to the use of anti-stripping additives, it does not provide a good simulation of factors playing roles in critical distresses such as rutting and raveling. What could be more effective is a simpler test allowing direct measure of adhesive bond between aggregates and asphalts. Such a test could replace the TSR in making a decision to require or not require the use of anti-stripping additive. The pull-off tensile strength test by the Pneumatic Adhesion Tensile Testing Instrument (PATTI) is also shown to give promising results.

Investigation on the effects of gradation and aggregate type to moisture damage of warm mix asphalt modified with Sasobit

Moisture damage is one of the major concerns for warm-mix asphalt (WMA) because it is hypothesised that the reduction in mixing temperature could adversely affect the moisture sensitivity of WMA. The aggregate type and their properties are also one important factor affecting the moisture damage of WMA. This study focused on understanding the effect of aggregate structure and its physical properties on the mechanism of moisture damage in WMA. This study evaluated the moisture sensitivity of hot-mix asphalt (HMA) and WMA as reflected in the permanent deformation. The effects of aggregate gradation and aggregate types on the moisture damage were also evaluated. The results from this study show that WMA is more resistant to permanent deformation than HMA as indicated by lower permanent strain rate and higher flow number (FN). Gradation has an effect on the permanent deformation in granite and slag mixes due to the difference in aggregate properties. WMA is more sensitive to moisture damage than HMA as shown in lower ratios of FN and permanent deformation rate. Fine-graded mixtures appear to have greater resistance to moisture damage than coarse-graded mixtures for both HMA and WMA. The result could be due to the different structure of air void distribution in the mixes of different gradation. It was found that the proper selection of aggregate type and aggregate structure could reduce the moisture damage problem of WMA.

Measurement of Visibility Loss Due to Splash and Spray: Porous, SMA and Conventional Asphalt Pavements

Road traffic accidents are a major problem for the safety, well-being and economies of Southeast Asian countries. In Thailand, many accidents are caused by environmental or road conditions. Poor visibility on wet pavement is a major cause of accidents. Accumulated water on wet pavement surfaces creates the ‘splash and spray’ effect, resulting in visibility loss. The main objective of this study is to develop simple methods for measuring and comparing visibility loss between conventional dense-graded asphalt, stone mastic asphalt (SMA) and porous asphalt (PA) pavements. The light reduction method (LRM) and the colour changing method (CCM) were found to be the most appropriate tests for the measurement of visibility loss. Test results from both methods reveal that visibility loss is significantly greater for the conventional dense-graded pavement than for the SMA and PA pavements. Models for predicting the percentage of visibility loss were also developed and can be useful for improving road safety.

Parameters to characterise the effects of Sasobit® content on the rheological properties of unaged and aged asphalt binders

Incorporation of warm asphalt additives in conventional asphalt binder affects its rheological properties. This paper presents two Superpave™ binder parameters that were used to characterise the rheological properties of PG64 and PG70 asphalt binders blended with various Sasobit® contents and subjected to high and intermediate temperatures as well as under different ageing conditions. The parameters used to characterise the binder rheology at high and intermediate temperatures were the non-dimensional viscosity gradient (∇ η S ) and non-dimensional Superpave™ rutting parameter (NSRP), respectively). The results indicated that the ∇ η S trends differ depending on binder types, test temperatures and ageing conditions. The NSRP exhibited a significantly different trend for each Sasobit® content, depending on binder type and ageing conditions.

Helmet Use and Effectiveness in Reducing the Severity of Head Injuries in Thailand

Head injuries due to motorcycle accidents are the main cause of death and disability among motorcycle users in Thailand. It is well known that wearing a helmet is one of the most effective ways to reduce the severity of head injuries due to motorcycle crashes. Although the helmet act for motorcyclists was enacted in Thailand in 1994, the rate of helmet use has not increased, and the rate of head injuries and fatalities due to motorcycle accidents has not been reduced. In this study, a field survey was conducted to observe helmet use in Bangkok and three other major regional provinces. The observation shows that the rate of helmet use is significantly low across the study areas. Age, location, time of day, and seating position significantly affect helmet use, whereas gender and the day of the week do not show any effect. The logit model was also used to evaluate the factors affecting helmet use on the basis of the injury surveillance data of motorcycle accident victims. Results indicate that the victims in the pillion, or passenger, position are less likely to use a helmet and those who ride during the nighttime, regardless of seating position, tend not to wear a helmet. To evaluate the effectiveness of helmet use and other related ways to reduce the severity of head injuries, the ordered logit regression technique was applied to the hospital-based data, using the data on patients suffering from head injuries due to road crashes. It is found that helmet use can reduce the severity of head injuries for motorcycle crash victims. The probability of fatality due to head injuries is reduced by 38% for motorcyclists wearing helmets. For motorcycle riders, helmets are found to be effective in protecting against head injuries, particularly for those riding under the influence of alcohol; the probability of death could be reduced by 43%. Those in the passenger position without helmets are more likely to sustain either serious or fatal head injuries than are riders without helmets. Results also indicate that a 58% reduction in the probability of fatality from head injuries is associated with the use of helmets by motorcycle passengers.

Does law enforcement awareness affect motorcycle helmet use? Evidence from urban cities in Thailand

Although helmet use has been compulsory for motorcycle drivers and passengers in Thailand since the enactment of the Helmet Act in 1994, recent surveys show that the prevalence of helmet usage remains low, particularly among passengers. This paper has sought to explore motorcyclists’ awareness of helmet law enforcement in Thailand and examine whether it affects their helmet use behaviour. A total of 2,429 drivers and 1,328 passengers in urban cities nationwide were interviewed in 2009, and the data were analysed using a multivariate ordered logit regression technique. About 60% of the drivers and only 28% of the passengers reported that they always wore a motorcycle helmet. Apart from basic demographics (i.e. age and gender) and riding frequency, our analysis reveals that the awareness of helmet law enforcement was among the contributing factors influencing the use of motorcycle helmets in Thailand. Regardless of riding position, the prevalence of helmet use tended to be greater among those frequently observing the police’s checkpoints for helmet wearing and those perceiving the high risk of being caught for non-helmet use. However, the use of helmets appeared to be lower among drivers who perceived the checkpoints to take place at the same times and locations, which were likely predicted. For motorcycle passengers, it was found that the low prevalence of helmet use was potentially attributable to the absence of knowledge on the compulsory helmet law for passengers and the perception that the law was not enforced by the police. Thus, if motorcycle helmet use in Thailand is to be increased, considerable efforts need to be given to increasing the perceived risk of apprehension for non-helmet use (e.g. more police presence and random scheduling of enforcement activities), improving the awareness of the existing helmet law for passengers, and ensuring that helmet wearing by passengers is more strictly enforced.

IDENTIFICATION OF FACTORS IN ROAD ACCIDENTS THROUGH IN-DEPTH ACCIDENT ANALYSIS

The rising trend of motorization and improving socio-economic status of Thai people directly influences the aggravating road safety situation with fatalities and permanently disabled injuries of about 130,000 and 500,000 respectively over the past decades. An estimated annual cost from road crashes amounts to about US

analysis of pedestrian accident costs in Sudan using the willingness-to-pay method

2,500 million, 3.4 percent of Gross National Product (GNP), undoubtedly inflicts Thailand with a burning public health concern in the South East Asian region. This paper addresses an in-depth study through crash investigation and reconstruction which has not yet been practised in Thailand to identify the contributory factors in road crashes by the concerned authorities. This research attempts to establish the linkage between the causes and consequences with event classification of an investigated case by highlighting the dynamic driving situation with initial traveling speed, pre-impact and post-impact speed of the involved vehicles to describe the crash scenario. Moreover, inaccurate risk assessment and late evasive action, absence of street-light facilities, inadequate lane marking and visibility were also outlined as major risk factors increasing the severity of crash and injury in this investigated case.

Effect of Seat Belt Use on Road Accidents in Thailand

The willingness-to-pay (WTP) with contingent valuation (CV) method has been proven to be a valid tool for the valuation of non-market goods or socio-economic costs of road traffic accidents among communities in developed and developing countries. Research on accident costing tends to estimate the value of statistical life (VOSL) for all road users by providing a principle for the evaluation of road safety interventions in cost-benefit analysis. As in many other developing countries, the economic loss of traffic accidents in Sudan is noticeable; however, analytical research to estimate the magnitude and impact of that loss is lacking. Reports have shown that pedestrians account for more than 40% of the total number of fatalities. In this study, the WTP-CV approach was used to determine the amount of money that pedestrians in Sudan are willing to pay to reduce the risk of their own death. The impact of the socioeconomic factors, risk levels, and walking behaviors of pedestrians on their WTP for fatality risk reduction was also evaluated. Data were collected from two cities-Khartoum and Nyala-using a survey questionnaire that included 1400 respondents. The WTP-CV Payment Card Questionnaire was designed to ensure that Sudan pedestrians can easily determine the amount of money that would be required to reduce the fatality risk from a pedestrian-related accident. The analysis results show that the estimated VOSL for Sudanese pedestrians ranges from US