الفهرس 
CHAPTER (1) INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 173 |  |  |
| | | from | 173 | | |
Abstract
It has long been regarded that friction coefficients play a significant role in influencing both the frequency and severity of traffic accidents. This widespread acceptance arises due to the road surface’s ability to facilitate the development of the skid resistance required for various vehicle manoeuvres, most notably braking and cornering. As a result, many highway authorities have set minimum friction requirements for road surfaces within their jurisdictions. Due to the most recent changes in policy and the incremental modernization of the vehicle fleet, this study sets out to re-investigate the relationship between friction coefficient and traffic accidents rates. where prescribed minimum friction coefficients are set too low, savings associated with traffic accidents rates may be possible through increasing friction coefficient requirements. Conversely, where friction coefficient requirements are set too high, savings may be possible through reduced road maintenance expenditure (Tim Nelson, April 2011).
This Thesis presents the evaluation of pavement friction values for selected Egyptian highways and relation between that friction and Cumulative Traffic (C.T.), road ages and accidents rates. Skid Resistance (S.R.) is the force developed when a tire that is fully or partially prevented from rolling slides along a pavement surface under lubricated conditions. Accidents due to skidding on pavement are a major concern of highway industries, these accidents are generally attributed to skid resistance deficiencies on the pavement surface, and hence the tire pavement friction interaction mechanism is one of the most important issues of safe vehicle operations on pavements. Different friction measuring devices have been developed to evaluate the frictional values of a pavement surface. The analysis has led to the development of a set of prediction models of friction values and other parameters which effecting on or affecting by friction values which mentioned above. The developed frictional models led to predict the actual friction values without losing time and cost in field measurements also passengers delay due to that tests.
Field tests were carried out using British Pendulum (B.P.) to converge some of selected Egyptian road types as rural desert, agriculture and urban roads. However; to overcome the possible effect of climatic variation most of the field tests were performed during summer at the same weather temperature at which surface skid resistance is expected at its low value as the highest value of asphalt viscosity records in summer season. Simple linear regression for friction values was used to check the correlation coefficient between this dependent variable and independent variables. Stepwise regression analysis was used to select the most statistically significant variables, based on the field investigation of pavement friction values using B.P. data, analysis of roads data, ANOVA and regression analysis. The most affected parameter from studied parameters on friction values was road age as friction value is depend on the mixture characteristic and that is gradually deteriorated by age, also it founded that friction value is one of the main elements of road accident’s reasons especially in urban roads.