الفهرس 
CHAPTER ONE: INTRODUCTINOnly 14 pages are availabe for public view
 |  | from | 280 |  |  |
| | | from | 280 | | |
Abstract
Two-lane, two-way roads represent a particular challenge to traffic
engineers as they constitute the majority of any network, e.g. about 75%
in Egypt. Measuring traffic performance at these facilities is a complex
issue due to their unique characteristics.
HCM2000 uses percent time spent following as the primary level-ofservice
measure for two-lane highways. As it is impractical to measure
the PTSF in the field, the HCM proposes using a surrogate measure,
percent followers (3-second rule). Studies revealed that the PTSF
equations produce results that are inconsistent with the 3-second rule.
Due such limitation in PTSF measure, alternative performance measures
were introduced by many authors in many countries to fit their local
conditions. It seems that, no studies suggested an alternative performance
measure to PTSF suitable for local condition in Egypt.
Therefore, the first goal of this research is to evaluate several
performance measures for estimating the traffic operational
characteristics on two-lane highways using data from eight rural roads in
Minoufiya Governorate, Egypt. The geometry and traffic data were
collected using manual field surveys and automatic traffic counters
respectively. The results showed that the three measures; follower
density, percent followers and percentage of vehicle impeded displayed
the highest associations with platooning variables respectively. Also,
traffic flow in the direction of travel, as a platooning variable, was found
to have the highest correlation with performance measures. Finally,
threshold values for different levels-of-service were proposed.
The second goal is studying the impact of the horizontal alignment
characteristics on performance measures of two-lane highway. The
ABSTRACT
iii
follower density, a new and promising performance measure in Egypt as
investigated from the first objective, is herein used. For this purpose, the
traffic data are collected from mid-tangent and mid-curve points at twelve
different sites with various horizontal alignment characteristics. The
results showed that the horizontal alignment characteristics have a
significant effect on the follower density, especially curve radius value. It
is also noticed that a value of horizontal curve radius from 400m nearly
seems to be a threshold of the significant impact of curve radius on traffic
performance. Also, the impact of horizontal alignment characteristics on
follower density was proposed at tangent and curve elements.
The third goal is studying the impact of highway geometry on
capacity and capacity loss in the presence of horizontal alignment by
comparing the percentage of capacity loss at two successive sections;
tangent and curve. A total number of twelve horizontal curves with
various geometric characteristics were chosen for this purpose. Each site
is consisted of one horizontal curve and the adjoining tangent. Capacities
of the road elements (tangent, horizontal curve) were estimated at each
site using polynomial modeling and multiple regression techniques. The
results showed that a capacity at tangent element depends on lane width,
shoulder width in the direction of flow and tangent length. However, a
capacity at curve element depends on lane width and curve radius.
Capacity loss is the negative difference between the capacity values
calculated at tangent and succeeding horizontal curve. Another approach
to investigate capacity loss directly was suggested. Capacity loss in this
approach depends on curve radius. Finally, a comparison between based
on observations and the two capacity loss approaches was carried out.
The results from based on observations were agreed with the two capacity
loss approaches.