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Quantitative and Qualitative Research Methods

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• Andrew England 5  

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Quantitative research uses methods that seek to explain phenomena by collecting numerical data, which are then analysed mathematically, typically by statistics. With quantitative approaches, the data produced are always numerical; if there are no numbers, then the methods are not quantitative. Many phenomena lend themselves to quantitative methods because the relevant information is already available numerically. Qualitative methods provide a mechanism to provide answers based on the collection of non-numerical data ‘i.e words, actions, behaviours’. Both quantitative and qualitative methodologies are important in medical imaging and radiation therapy.   In some instances, both quantitative and qualitative approaches can be combined into a mixed-methods approach. This chapter discusses all methodological approaches to research from both medical imaging and radiation therapy perspectives.  

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Alzyoud, K., Hogg, P., Snaith, B., Flintham, K., & England, A. (2019). Impact of body part thickness on AP pelvis radiographic image quality and effective dose. Radiography, 25 (1), e11–e17. https://doi.org/10.1016/j.radi.2018.09.001

Article   CAS   PubMed   Google Scholar  

Banks, E., Beral, V., Cmeron, R., et al. (2001). Comparison of various characteristics of women who do and do not attend for breast cancer screening. Breast Cancer Research, 4 , R1. https://doi.org/10.1186/br418

Article   PubMed   PubMed Central   Google Scholar  

Benfield, S., Hewis, J. D., & Hayre, C. M. (2021). Investigating perceptions of ‘dose creep’ amongst student radiographers: A grounded theory study. Radiography, 27 (2), 605–610. https://doi.org/10.1016/j.radi.2020.11.023

Booth, L., Henwood, S., & Millker, P. K. (2017). Leadership and the everyday practice of Consultant Radiographers in the UK: Transformational ideals and the generation of self-efficacy. Radiography, 23 (2), 125–129. https://doi.org/10.1016/j.radi.2016.12.003

Bristowe, K., Selman, L., & Murtagh, F. E. M. (2015). Qualitative research methods in renal medicine: An introduction. Nephrology, Dialysis, Transplantation, 30 (9), 1424–1431. https://doi.org/10.1093/ndt/gfu410

Article   PubMed   Google Scholar  

Cuthbertson, L. M. (2019). The journey to radiographer advanced practice: A methodological reflection on the use of interpretative phenomenological analysis to explore perceptions and experiences. Journal of Radiotherapy in Practice, 19 , 116–121. https://doi.org/10.1017/S1460396919000621

Article   Google Scholar  

Decker, S. (2009). The lived experience of newly qualified radiographers (1950–1985): An oral history of radiography. Radiography, 15 (1), e72–e77. https://doi.org/10.1016/j.radi.2009.09.009

Dillman, J. R., Ellis, J. H., Cohan, R. H., Strouse, P. J., & Jan, S. C. (2007). Frequency and severity of acute allergic-like reactions to gadolinium-containing IV contrast media in children and adults. American Journal of Roentgenology, 189 (6), 1533–1538. https://doi.org/10.2214/AJR.078.2554

Hart, D., Hillier, M. C., & Wall, B. F. (2009). National reference doses for common radiographic, fluoroscopic and dental X-ray examinations in the UK. The British Journal of Radiology, 82 , 1–12. https://doi.org/10.1259/bjr/12568539

Hayre, C. M., Blackman, S., Carlton, K., & Eyden, A. (2018). Attitudes and perceptions of radioigraphers applying lead (Pb) in general radiography: An ethnographic study. Radiography, 24 (1), e13–e18. https://doi.org/10.1016/j.radi.2017.07.010

Mercer, C. E., Hogg, P., Lawson, R., Diffey, J., & Denton, E. R. E. (2013). Practitioner compression force variability in mammography: A preliminary study. The British Journal of Radiology, 86 (1022), 20110596. https://doi.org/10.1259/bjr.20110596

Article   CAS   PubMed   PubMed Central   Google Scholar  

Nijssen, E. C., Rennenberg, R. J., Nelemans, P. J., Essers, B. A., Jannseen, M. M., Vermeeren, M. A., et al. (2017). Prophylactic hydration to protect renal function from intravascular iodinated contrast materials in patients at high risk of contrast-induced nephropathy (AMACING): A prospective, randomised, phase 3, controlled trial, open-label, non-inferiority trail. Lancet, 389 (10076), 1312–1322. https://doi.org/10.1016/S0140-6736(17):30057-0

Rosenkrantz, A. B., & Pysarenko, K. (2016). The patient experience in radiology: Observations from over 3,500 patient feedback reports in a single institution. Journal of the American College of Radiology, 13 (11), 1371–1377. https://doi.org/10.1016/j.jacr.2016.04.034

Sternberg, C. N., Hawkins, R. E., Wagstaff, J., Salman, P., Mardiak, J., Barrios, C. H., et al. (2013). A randomised, double-blind phase III study of pazopanib in patients with advanced and/or metastatic renal cell carcinoma: Final overall survival results and safety update. European Journal of Cancer, 49 (6), 1287–1296. https://doi.org/10.1016/j.ejca.2012.12.010

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Robert Davidson

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England, A. (2021). Quantitative and Qualitative Research Methods. In: Seeram, E., Davidson, R., England, A., McEntee, M.F. (eds) Research for Medical Imaging and Radiation Sciences. Springer, Cham. https://doi.org/10.1007/978-3-030-79956-4_5

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Chapter 5: Conclusion, Interpretation and Discussion

Introduction.

The following chapter concludes this report. A summary of the research is presented, and findings of the study are discussed and interpreted. The significance of this research in the immediate context of El Gallo and in the field of low-income housing is examined. Recommendations for further research end the chapter.

The scope of the following conclusions is limited to the context and historical characteristics of El Gallo. Thus, applied to other situations, these conclusions may yield incorrect assumptions. Still, these conclusions are relevant to the process of dwelling evolution in progressive development projects.

5.1 Summary of Research

This study observed the process of dwelling evolution in progressive development projects. The literature review was concentrated on the process of progressive development occurring in planned sponsored projects. It was found that, based on observations of the informal settlement process, progressive development under different contextual conditions was not questioned, and its benefits were taken for granted. Studies in the area were reduced to the period of improvement up to the time when the dwelling was physically consolidated. Longer term evaluation of progressive development projects were not found.

Research was undertaken on a 27-year-old progressive development project in Venezuela. The intention was to observe the process of dwelling evolution and the kind of housing that was being produced under progressive urban development projects on a long-term basis. The case study showed dwellings built with different initial levels of user-participation. Dwelling evolution was observed in a survey sample using parameters relevant to the case study (i.e., area increase, dwelling spatial growth and plot occupation, and changes in the functional structure).

Survey dwellings followed identifiable patterns of evolution in size, spatial structure and use-layout. Patterns were affected by aspects of the surrounding context and by aspects inherent to characteristics of the initial dwelling. Consequently, different dwelling groups showed different processes of progressive development.

5.2 Discussion and Interpretation of Findings.

As progressive developments, dwellings at El Gallo were able to adopt new and diverse roles along their whole process of evolution. In this section, relevant issues of the process of dwelling evolution observed at El Gallo are discussed. The first concerns the role of the non-permanent structure in the context of El Gallo as a sponsored progressive development project. The second comments on the process of dwelling evolution that followed the construction of the permanent structure.

In principle, non-permanent structures at El Gallo were similar to ranchos built in informal settlements. Ranchos at El Gallo served as primary shelters while more basic household priorities were met (i.e., services and infrastructure were provided, sources of income were found and generated, and even a favourable social environment was developed among neighbours). However, the majority of tin shacks were neither considerably increased nor upgraded with better materials even when they were used for long periods of time. This fact, together with the sudden change in the pace of development caused by the construction of a very complete permanent dwelling and subsequent removal of the rancho, had no connection with the gradual process of shack replacement observed in invasion settlements of Ciudad Guayana during this study (Portela, M. 1992). Neither did this process have a relationship with the system of "piecemeal construction" described by several housing researchers as characteristic of low-income dwellers.

The shanties were... housing in process of improvement. In particular the piecemeal system of building afforded great advantages to those who, like most of the poor in developing societies, have great variations in income from month to month (Peattie L. 1982:132).

Under El Gallo conditions of land security, ranchos did not show consolidation, and revealed their transient character because they were eventually substituted by permanent structures. The non-permanent structure revealed the primary household's aspiration for a minimum satisfactory habitable area. However, besides basic shelter during the initial stage, ranchos served to the purposes of capital accumulation that eventually allowed households to buy a basic unit according to official standards, or building a bigger, more complete first permanent structure. The size of ranchos reflected households' aspirations for the permanent dwelling, that is,smaller ranchos were substituted by basic units of the housing programs. Instead larger ranchos were substituted by large self-produced dwellings.

It is difficult to ascertain why ranchos were removed when they could have been kept as part of the dwelling, as in fact did a minority of households (2 cases). Is a fact that the temporary materials of ranchos contributed to their deterioration that ended with the total removal of the rancho. However, an idea that may have contributed to the demolition of the rancho was the household's adoption of the planner's belief that ranchos were a bad but necessary step on the way to obtaining permanent housing. Thus, once the permanent dwelling was built, the price households paid to gain credibility (i.e., that this stage was reached) was the demolition of the rancho itself. This interpretation can be specially true for Ciudad Guayana, where dwellings of certain quality such as those of El Gallo were seen as "casas" or houses. Instead, structures of similar quality in the hills of cities such as Caracas were still considered ranchos. In the long run, informal settlements obtained the largest benefits from this process because they gained far more official tolerance and social credibility (i.e., that shacks were actually temporary means of residence towards good-quality housing).

Those who lived in smaller ranchos improved their spatial conditions by moving to the small basic dwellings. Those who occupied bigger ranchos built bigger dwellings by themselves. Still, some households built their dwellings without going through the rancho stage. Self-produced dwellings followed the formal models either to gain the government's credibility of user commitment to build "good" government-like housing, or because households believed so. Imitation of the formal models, however, varied according to the builder's interpretation. For instance, the pattern of the detached dwelling was adopted, but often one of the side yards was reduced to a physical separation between the dwelling and the plot separation wall. More effective interpretations involved enlarging the front porch or using the central circulation axis to allow easy extension in the future.

The building approach of the permanent structure influenced the process of evolution that followed. Basic units built by the housing agencies had a compact, complete layout with higher standards of construction; however, aspects of the design, such as internal dimensions, were inadequate for household criteria, and the layout was not well adapted. Dwellings built according to provided plans and specificationshad similar problems, but households enlarged spaces and modified layouts when they were building the units. The level of construction standards was also reduced since the lateral façades of some dwellings were unfinished. Dwellings built totally by self-help means were the largest permanent structures. Aspects of the design of the first permanent structure allowed easy extension of the dwelling towards open areas of the plot. More user participation was reflected in straight-forward processes of evolution without internal modifications, and fewer stages to reach the current houseform.

5.3 Significance of the Study

While this study acknowledges again the effectiveness of progressive development in the housing system, it shows how dwelling evolution in progressive development projects can have different characteristics produced by internal and external interventions. Usually, projects are designed and launched to reproduce certain desirable outcomes and meet specific expectations. However, conditions prevailing in these projects and sometimes strategies that are introduced to "improve," "speed up" or make more "efficient" the process of evolution can affect the outcome in many different ways. This study showed how contextual characteristics of El Gallo, as well as the design and level of user participation in the initial permanent dwelling, affected successive stages of progressive development. However, it is important to recognize that are other issues beyond the spatial aspects that are intrinsically related with the evolution of the dwellings and that were not included within the scope of these particular research (i.e., household's changes in income, size, and age or gender structure).

The findings at El Gallo add modestly to the body of knowledge of literature on progressive development. Progressive Urban Development Units, UMUPs , have been the main housing strategy in Ciudad Guayana these last years, and they are likely to keep being used. Simple facts such as knowing the characteristics of the additions and modifications that households make to their dwellings over time can be the basis for more assertive actions supporting or enforcing progressive development activities. Understanding the process of dwelling evolution in low-income developments would be an effective way to help the process that, in the case of Ciudad Guayana, zonings and bylaws have been unable to regulate.

5.4 Recommendations for Further Research

Long term assessments are particularly constrained by the availability and reliability of recorded data. The frequency, and often the methodology, in which censuses and surveys are made do not always suit the purposes of this kind of research. Household interviews are very important, but they may become troubled by informant's limited memories and the continuity of the household in the dwelling. Aerial documentation, if available, represents one of the most reliable sources to observe physical change. Nevertheless, a careful and detailed process of observation of aerial data becomes very time consuming. For similar studies, a first phase in which the housing diversity is identified in the aerial data according to the selected criteria, would allow to reduce the number of detailed survey samples needed, thus considerably reducing the time of data collection.

In the context of Ciudad Guayana, further studies of the non-permanent dwelling in recent UMUPs would reveal new insights into the function of these structures in progressive development projects. This would be essential especially if any kind of initial aid is to be provided. On the other hand, following the growth of progressive developments is necessary if services and infrastructure are, as they are now, the responsibility of the local government. Identifying the producers of physical evolution -- i.e., the drivers and catalysts of change -- would be an important step for further research. An interesting step within this trend could be to ascertain the extent in which other household processes -- family growth, income increase and economic stability, household aging, changes in the household composition (single- to multi- family), etc., affect the process of dwelling evolution.

In the context of low-income housing, the process of progressive development needs further understanding. As in Ciudad Guayana, progressive development is likely to be the main housing strategy for other developing countries in the near future. Local authorities would do well to follow the evolution of settlements and to identify real household needs, and the consequences of public and/or private interventions in low-income settlements. Perhaps the most important learning of this study is that the experience of El Gallo acknowledges again the dynamic participation of the low-income households under different conditions, and still leaves wide room for a positive participation for the many other actors in the evolving urban entity.

. Notes for Chapter V

1 Dodge reports that some settlers of Ciudad Guayana kept the rancho and rented it to poorer families (Dodge,C. 1968:220). This attitude has been more common in other progressive development projects. The Dandora site and services also encouraged the construction of temporary shacks while the permanent dwelling was built. However, non-permanent structures remained to be rented or used as storage areas even after the permanent dwelling was built (McCarney, P.L. 1987:90).

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Minimum cost housing group.

Improved Surface Drainage of Pavements: Final Report (1998)

Chapter: chapter 5 summary, findings, and recommendations.

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

CHAPIER 5 SI~MARY, FINDINGS, AND RECOMMENDATIONS SUGARY The primary objective of this research was to identify unproved methods for draining rainwater from the surface of multi-lane pavements and to develop guidelines for their use. The guidelines, along with details on the rationale for their development, are presented in a separate document' "Proposed Design Guidelines for Improving Pavement Surface Drainage" (2J. The guidelines support an interactive computer program, PAVDRN, that can be used by practicing engineers In the process of designing new pavements or rehabilitating old pavements' is outlined In figure 39. The intended audience for the guidelines is practicing highway design engineers that work for transportation agencies or consulting firms. Improved pavement surface drainage is needed for two reasons: (~) to minimize splash and spray and (2) to control the tendency for hydroplaning. Both issues are primary safety concerns. At the request of the advisory panel for the project, the main focus of this study was on ~mprov~g surface drainage to mammae the tendency for hydroplaning. In terms of reducing the tendency for hydroplaTuT g, the needed level of drainage is defined in terms of the thickness of the film of water on the pavement. Therefore, the guidelines were developed within the context of reducing the thickness of the water film on pavement surfaces to the extent that hydroplaning is unlikely at highway design speeds. Since hydroplaning is ~7

DESIGN CRITERIA Pavement Geometry Number of lanes Section type - Tangent - Horizontal curve - Transition - Vertical crest curve - Vertical sag curve Enviromnental oramaters Rainfall intensity ~ Temperature Pavement Tvpe Dense-graded asphalt Porous asphalt Portland cement concrete ~ Grooved Portland cement concrete Desion Soeed Allowable speed for onset of hydroplaning Recommend Desion Changes Alter geometry Alter pavement surface Add appurtenances Groove (Portland cement concrete) CALCULATIONS Lenoth of flow path Calculate on basis of pavement geometry IT Hydraulic Analvses .  No? Water film thickness Equation No. 10 Equation No.'s. 16-19 1 Hvdroolanino Analvsis Hydroplaning speed Equation No.'s 21-24 Rainfall Intensity Equation No. 25 -A I / Meet Design ~ \ Cntena? / \<es? Accent Desinn | Figure 39. Flow diagram representing PAVI)RN design process In "Proposed Guidelines for Improving Pavement Surface DrmT~age" (2). 118

controlled primarily by the thickness of the water film on the pavement surface, the design guidelines focus on the prediction and control of ache depth of water flowing across the pavement surface as a result of rainfall, often referred to as sheet flow. Water film thickness on highway pavements can be controlled In three fundamental ways, by: I. Minimizing the length of the longest flow path of the water over We pavement and thereby the distance over which the flow can develop; 2. Increasing the texture of the pavement surface; and 3. Removing water from the pavement's surface. In the process of using PAVDRN to implement the design guidelines, the designer is guided to (~) minimize the longest drainage path length of the section under design by altering the pavement geometry and (2) reduce the resultant water film thickness that will develop along that drainage path length by increasing the mean texture depth, choosing a surface that maximizes texture, or using permeable pavements, grooving, and appurtenances to remove water from the surface. Through the course of a typical design project, four key areas need to be considered in order to analyze and eventually reduce the potential for hydroplaning. These areas are: ~9

I. Environmental conditions: 2. Geometry of the roadway surface; 3. Pavement surface (texture) properties; and 4. Appurtenances. Each of these areas and their influence on the resulting hydroplaning speed of the designed section are discussed In detail In the guidelines (21. The environmental conditions considered are rainfall ~ntensibr and water temperature, which determines the kinematic viscosity of the water. The designer has no real control over these environmental factors but needs to select appropriate values when analyzing the effect of flow over the pavement surface and hydroplaning potential. Five section types, one for each of the basic geometric configurations used In highway design, are examined. These section are: 1. TaIlgent; 2. Superelevated curve; 3. Transition; 4. Vertical crest curve; and 5. Vertical sag curve. 120

Pavement properties that affect the water fihn thickness mclude surface characteristics, such as mean texture depth and grooving of Portland cement concrete surfaces, are considered In the process of applying PAVDRN. Porous asphalt pavement surfaces can also reduce He water film thickness and thereby contribute to the reduction of hydroplaning tendency and their presence can also be accounted for when using PAVDRN. Finally, PAVDRN also allows the design engineer to consider the effect of drainage appurtenances, such as slotted drain inlets. A complete description of the various elements that are considered In the PAVDRN program is illustrated In figure 40. A more complete description of the design process, the parameters used in the design process, and typical values for the parameters is presented In the "Proposed Design Guidelines for Improving Pavement Surface Drainage" (2) alla in Appendix A. fIN1)INGS The following findings are based on the research accomplished during the project, a survey of the literature, and a state-of-the-art survey of current practice. I. Model. The one~unensional mode} is adequate as a design tool. The simplicity and stability of the one~imensional mode} offsets any increased accuracy afforded by a two-d~mensional model. The one~mensional model as a predictor of water fiDn thickness and How path length was verified by using data from a previous study (11). 121

No. of Planes Length of Plane Grade Step Increment Wdth of Plane Cross Slope Section T,rne 1) Tangent 2) Honzontal Curare 3) Transition 4) Vertical Crest 5) Vertical Sag U=tS 1)U.S. 2) S. I. Rainfall Intenstity ~ , \ |Kinematic Viscosity |Design Speed Note: PC = Point of Curvature PI. = Point of Tangency PCC = Portland cement concrete WAC = Dense graded asphalt concrete 0GAC = 0pcn~raded asphalt concrete where OGAC includes all types of intentally draining asphalt surfaces GPCC = Grooved Ponland cement concrete Taneent Pavement Type Mean Texture Depth 1) PCC 2) DGAC 3) OGAC 4) GPCC Horizontal Cun~c  Grade Cross Slope Radius of Cunran~re Wdth Pavement Type _ 2) DGAC 3) OGAC 4) GPCC Mean Texture Depth Step Increment _ Transition Length of Plane Super Elevation Tangent Cross Slope Tangent Grade width of Curve Transition Width Pavement Type_ 1) PCC 3) OGAC 4) GPCC Mean Texture Depth Step Increment Horizontal Length Cross slope width PC Grade PI' Grade Elevation: Pr-PC Vertical Crest Flow Direction Step Increment Pavement Type 1) PC Side I 2) PI. Side | 1)PCC 2) DGAC 3) OGAC 4) GPCC Mean Tex~rc Depth _ _ ~ Figure 40. Factors considered in PAVDRN program. 122 ~1 r - . , Vertical Sad | Horizontal Length | Cross slope Wldth PC Grade PI Grade Elevation: PIE Flow Direction  Step Increment / Stored :_ ~ cats ~ 1) PC Side | 2) PI Side | . Pavement Typed 1) PCC 3) OGAC 14) GPCC Mean Texture Depth I I

~ Stored data V ~ 3 L IN1T For use with a second nut using data from the first run.) , 1 EPRINT (Echos input to output ) 1 CONVERT (Converts units to and from SI and English.) ~ , ADVP  (Advances Page of output.) KINW (Calculates Minning's n, Water Film Thickness (WEIR), and Hydroplaning Speed UPS).) , EDGE (Determines if flow has reached the edge of the pavement.) out roar Figure 40. Factors considered in PAVDRN program (continued). 123

2. Occurrence of Hydropl~r g. In general, based on the PAVDRN mode! and the assumptions inherent in its development, hydroplaning can be expected at speeds below roadway design speeds if the length of the flow path exceeds two lane widths. 3. Water Film Thickness. Hydroplaning is initiated primarily by the depth of the water film thickness. Therefore, the primary design objective when controlling hydroplaning must be to limit the depth of the water film. 4. Reducing Water Film Thickness. There are no simple means for controlling water John thickness, but a number of methods can effectively reduce water film thickness and consequently hydroplaning potential. These include: Optimizing pavement geometry, especially cross-slope. Providing some means of additional drainage, such as use of grooved surfaces (PCC) or porous mixtures (HMA). Including slotted drains within the roadway. 5. Tests Needed for Design. The design guidelines require an estimate of the surface texture (MTD) and the coefficient of permeability Porous asphalt only). The sand patch is an acceptable test method for measuring surface texture, except for the more open (20-percent air voids) porous asphalt mixes. In these cases, an estimate of the surface texture, based on tabulated data, is sufficient. As an alternative, 124

sand patch measurements can be made on cast replicas of the surface. For the open mixes, the glass beads flow into the voids within the mixture, giving an inaccurate measure of surface texture. Based on the measurements obtained In the laboratory, the coefficient of permeability for the open-graded asphalt concrete does not exhibit a wide range of values, and values of k may be selected for design purposes from tabulated design data (k versus air voids). Given the uncertainty of this property resulting from compaction under traffic and clogging from contaminants and anti-skid material, a direct measurement (e.g., drainage lag permeameter) of k is not warranted. Based on the previous discussion, no new test procedures are needed to adopt the design guidelines developed during this project. 6. Grooving. Grooving of PCC pavements provides a reservoir for surface water and can facilitate the removal of water if the grooves are placed parallel to the flow oath. Parallel orientation is generally not practical because the flow on highway pavements is typically not transverse to the pavement. Thus, the primary contribution offered by grooving is to provide a surface reservoir unless the grooves comlect with drainage at the edge of the pavement. Once the grooves are filled with water, the tops of the grooves are the datum for the Why and do not contribute to the reduction in the hydroplaning potential. 125

7. Porous Pavements. These mixtures can enhance the water removal and Hereby reduce water film tHch~ess. They merit more consideration by highway agencies In the United States, but they are not a panacea for eliminating hydroplaning. As with grooved PCC pavements, the internal voids do not contribute to the reduction of hydroplaning; based on the field tests done In this study. hv~ronImiina can be if, , , ~ expected on these mixtures given sufficient water fiLn thickness. Other than their ability to conduct water through internal flow, the large MTD offered by porous asphalt is the main contribution offered by the mixtures to the reduction of hydroplaning potential. The high-void ~ > 20 percent), modified binder mixes used In Europe merit further evaluation in the United States. They should be used In areas where damage from freezing water and the problems of black ice are not likely. 8. Slotted Drains. These fixtures, when installed between travel lanes, offer perhaps the most effective means of controlling water film thickness from a hydraulics standpoint. They have not been used extensively In the traveled lanes and questions remain unanswered with respect to their installation (especially in rehabilitation situations) and maintenance. The ability to support traffic loads and still maintain surface smoothness has not been demonstrated and they may be susceptible to clogging from roadway debris, ice, or snow. 126

RECOMMENDATIONS AND CONCLUSIONS The following recommendations are offered based on the work accomplished during this project and on the conclusions given previously: I. Implementation. The PAVDRN program and associated guidelines need to be field tested and revised as needed. The program and the guidelines are sufficiently complete so that they can be used in a design office. Some of the parameters and algorithms will I~ely need to be modified as experience is gained with the program. 2. Database of Material Properties. A database of material properties should be gathered to supplement the information contained in PAVDRN. This information should Include typical values for the permeability of porous asphalt and topical values for the surface texture (MTD) for different pavement surfaces to include toned Portland cement concrete surfaces. A series of photographs of typical pavement sections and their associated texture depths should be considered as an addition to the design guide (21. 3. Pavement Geometry. The AASHTO design guidelines (~) should be re-evaluated In terms of current design criteria to determine if they can be modified to enhance drainage without adversely affecting vehicle handling or safety. ~27

4. Use of appurtenances. Slotted drams should be evaluated In the field to determine if they are practical when Installed In the traveled way. Manufacturers should reconsider the design of slotted drains and their Installation recommendations currently In force to maximize them for use In multi-lane pavements and to determine if slotted drains are suitable for installations In the traveled right of way. 5. Porous Asphalt Mixtures. More use should be made of these mixtures, especially the modified high a~r-void mixtures as used In France. Field trials should be conducted to monitor HPS and the long-term effectiveness of these mixtures and to validate the MPS and WDT predicted by PAVDRN. 6. Two-D~mensional Model. Further work should be done with two~mensional models to determine if they improve accuracy of PAVDRN and to determine if they are practical from a computational standpoint. ADDITIONAL STUDIES On the basis of the work done during this study, a number of additional items warrant furler study. These Include: 1. Full-scale skid resistance studies to validate PAVDRN in general and the relationship between water film thickness and hydroplaning potential in particular are needed in light of the unexpectedly low hvdronlanin~ speeds predicted during 128 , . ~. , ~

this study. The effect of water infiltration into pavement cracks and loss of water by splash and spray need to be accounted for In the prediction of water fihn Sickness. Surface Irregularities, especially rutting, need to be considered in the prediction models. 2. Field trials are needed to confirm the effectiveness of alternative asphalt and Portland cement concrete surfaces. These include porous Portland cement concrete surfaces, porous asphalt concrete, and various asphalt m~cro-surfaces. 3. The permeability of porous surface mixtures needs to be confirmed with samples removed from the field, and the practicality of a simplified method for measuring in-situ permeability must be investigated and compared to alternative measurements, such as the outflow meter. 4. For measuring pavement texture, alternatives to the sand patch method should be investigated, especially for use with porous asphalt mixtures. 129

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