Mahmoud Saffarzadeh, Maghsoud Pooryari,
Volume 3, Issue 2 (6-2005)
Abstract
This paper specifies the relationship among various factors contributing to road accidents
including geometrical design characteristics, environmental and traffic specifications, by multiple
regression analysis. The main objective of this paper is identification of problems associated with
the safety issue of road networks by application of accident prediction models. Data from previous
accidents were used to develop the models.
Results of this study showed that the rate of road accidents is to a large extent dependent on the rate
of traffic volume. Type of road and land-use are other important factors influencing the number and
intensity of accidents. The mountainous roads in this respect require special attention regarding
their safety factors. The quantitative rate of road safety upgrading has also been specified by adding
traffic lanes in road networks.
H. Behbahani, S.m. Elahi,
Volume 4, Issue 1 (3-2006)
Abstract
To properly plan for construction, repair, maintenance, and reconstruction of highways the
minimum acceptable roadway condition is needed information. This, along with other pavement
management tools, will help select the most desirable roadway alternatives. In this research the
minimum acceptable conditions are developed based on an opinion survey of non-technical but
high-level decision makers. Roadway roughness, expressed as international roughness index (IRI),
is used as the measurement criteria. Because IRI is a widely known, acceptable, and a uniformly
measurable index, it is used for the purpose of this research. The minimum IRI values developed
here will help managers, planners, and engineers in prioritizing their plans and projects. Iran has
a central planning system, hence having a minimum acceptable IRI will help in producing
homogeneity in decision making. A questionnaire is sent to top level and influential managementlevel
officials who have a decisive input in highway matters. The officials are asked to choose the
minimum acceptable service level of different types of roadways and classifications. Naturally,
roadways with higher levels of importance would require higher service levels. The answers to the
survey questionnaires are investigated to determine a preferred minimum acceptable roadway
condition. The IRI is computed using a mechanical device enabling a more uniform data collection.
The IRI was first proposed by The World Bank as a standard roughness statistic. Extensive research
has proven that the IRI can be related to pavement condition. The result of the opinion survey is
investigated to determine the minimum levels acceptable for each category. The responses show
distinct preference patterns for most of the roadway types. Survey results are investigated by plotting
and analyzing them. Based on road user’s perception of roadway condition using guidelines from
AASHTO, the Corp of Engineers, and related research work. The appropriate IRI limits and ranges
are determined for Iran’s highways. These values are adjusted to obtain final values for Iran. The
result, shown in a table, gives upper and lower IRI values accepted and recommended for Iran’s
highways. The result of this research work is specifically useful in developing specifications for new
pavement design, accepting new pavement from contractors, pavement management, highway
planning, and in roadway life cycle cost analysis decision making. The results are subject to
refinement over time.