ICAHETS - 2017http://dl.lib.uom.lk/handle/123/190022024-03-28T13:24:46Z2024-03-28T13:24:46ZProceedings of Advances in Highway Engineering & Transportation Systems 2017 [Pre Text]http://dl.lib.uom.lk/handle/123/190792023-05-08T03:41:34Z2017-01-01T00:00:00ZProceedings of Advances in Highway Engineering & Transportation Systems 2017 [Pre Text]
Pasindu, HR
2017-01-01T00:00:00ZMinimizing highway alignment cost by optimizing horizontal curve radiusSushma, MBMaji, Ahttp://dl.lib.uom.lk/handle/123/190782023-02-20T09:38:52Z2017-07-01T00:00:00ZMinimizing highway alignment cost by optimizing horizontal curve radius
Sushma, MB; Maji, A
Pasindu, HR
In practice, the task of designing the horizontal alignment of a highway is done manually
based on experience and engineering judgement. As a result, the work is both time and
resource consuming and relies heavily on human expertise. This paper presents a general
formulation for optimization of horizontal alignment, composed of tangential segments and
circular curves. It consists of a constrained optimization problem where the objective
function is to minimize the overall cost of the horizontal alignment. These constraints are
imposed by curvatures, geometric guidelines, the presence of inaccessible regions, etc. In
addition to construction costs, facts considered by this model also include highway geometric
code requirements. The paper mainly focuses on fitting the curves with appropriate radius
between the tangential sections obtained by connecting the optimum set of point of
intersections (Pis). The available methods consider radius of the curves as a constant value,
which also acts as a constraint while developing an optimal alignment. Application of the
model to a real-world study area is also presented in this paper, along with a comparative
study with AutoCAD Civil-3D.
2017-07-01T00:00:00ZEffect of traffic composition on capacity of two-way two-lane, roads under mix traffic conditionRajapaksha, RPGKSBandara, JMSJhttp://dl.lib.uom.lk/handle/123/190772022-10-12T03:30:59Z2017-01-01T00:00:00ZEffect of traffic composition on capacity of two-way two-lane, roads under mix traffic condition
Rajapaksha, RPGKS; Bandara, JMSJ
Pasindu, HR
Traffic performance of a road section is expressed in terms of Level of Service (LOS). The
Highway Capacity Manual (HCM) developed by the Transportation Research Board of the
National Academies of Science in the United States provides procedures to determine LOS
based on analysis of capacity of a road. It divides the quality of flow into six levels ranging
from level A to F. These definitions of quality are based on measures of effectiveness of the
road which include speed, travel-time, density and delay.
Road development authorities in Sri Lanka are adopting the methodologies given in the HCM
due to the lack of guidelines specific for the country. However, the HCM methodologies may
not depict the correct traffic performance of roads owing to the nature of the mix of vehicle
types in the traffic stream, the lack of lane discipline and irregular road side activities. This
may lead to incorrect decisions in planning, designing, maintenance, rehabilitation, and
operation of roads. Therefore, it is necessary to study traffic performance in Sri Lanka, and to
evaluate the transferability of methods used in other similar countries in order to develop
appropriate and applicable approach to mix traffic Condition. Subsequently, in order to
evaluate traffic performance, it is important to study about operational characteristics of
traffic stream. In a pilot study under this work, capacity of a road was found to be affected by
the traffic composition and control condition. Therefore, characteristics of vehicle
composition in different capacities have been considered and study was focused to two waytwo
lane roads.
Different size, power, and maneuverability performance of vehicles cause significant level of
friction to the movement of other vehicles in a mix traffic stream. For an example, in a high
traffic volume stream, a large proportion of motorized two wheelers and three wheelers are
able to move with speeds closer to their free speeds due to the ability of utilizing smaller gaps
in the traffic stream, while the large-size vehicles are subjected to significant speed reduction.
Characteristics of fundamental traffic flow parameters (Speed, Density and Flow) in traffic
streams with different compositions of vehicles were studied. One-Sample Kolmogorov
Smirnov test was performed to check normality of speed of collected data samples under prevailing conditions and it has shown that speed distribution is significantly deviate from
normality (P-value < 0.05) under different compositions and traffic volumes. It is observed
that speed distribution shows bi-modal distribution in roads which
wheelers and three wheelers. One-way analysis of variance (One-way ANOVA) tests was
carried for speed characteristics of group of two wheelers, three wheelers and four wheelers.
Null hypothesis (Ho) that there will be no significant difference between different groups of
vehicle speed sample means was rejected with 95% confidence level (P-value < 0.05).
Therefore, vehicle composition has described as separate groups of two wheelers, three
wheels and four wheelers. Modified continuity equation for heterogeneous driver population
was used to calculate densities of traffic streams. Different traffic flow models which
used to model two-lane traffic flow behavior had been tested under prevailing conditions.
Greenshield traffic flow model has showed strong correction between flow and speed and it
was chosen to develop speed-flow models. Finally, empirical speed - density and speed -
flow curves were developed for different compositions of vehicles in order to evaluate the
capacity variations under mix traffic condition.
2017-01-01T00:00:00ZPassing sight distance: adequacy of aashto criteria for two lane roads in Sri LankaMasakorala, RMampearachchi, WKhttp://dl.lib.uom.lk/handle/123/190762022-10-12T03:31:27Z2017-07-01T00:00:00ZPassing sight distance: adequacy of aashto criteria for two lane roads in Sri Lanka
Masakorala, R; Mampearachchi, WK
Pasindu, HR
Freedom of overtaking maneuvers on a two-lane highway indicates the Level of Service of
that particular highway according to the Highway Capacity Manual, 2010. Therefore, an
adequate minimum Passing Sight Distance (PSD) would economically increase the
percentage of passing zones, ultimately the highway capacity as well. Initially, American
Association of State Highways Officials (AASHTO) provided a guidance for minimum PSD
design criteria for passenger cars in 1954. Later, more conservative and comprehensive
models and concepts were presented by Lieberman (1982), Glennon (1988), Hassan et al.,
(1996), and Harwood et al., (2008) etc. Typically, the effectiveness of analytical models was
evaluated based on the realization of safe overtaking mechanism with a wide range of human
and vehicle related parameters.
This paper will present an analytical model derived and validated using empirical data for
passenger cars and evaluation of the suitability of AASHTO and proposed model for local
traffic conditions. The filed investigation was done using two test vehicles and a GPS data
logger, on selected A & B class highways in Western and Southern Provinces of the country.
The modal basis - idealized overtaking maneuver - was developed with field observations
and consequently validated with empirical data. When compared to the resultant PSD values
with AASHTO, new model clearly presented significantly conservative values than
AASHTO for design speeds less than 80km/h. To evaluate both models for safety, a
reliability index was calculated relevant to the actual PSD demand on local highways.
According to the results reliability of AASHTO model extremely depreciated with increasing
design speed while new model reach to a constant value at around 60km/h. Therefore, as a
conclusion the adaptation of AASHTO guidelines for highway design purposes can be
justifiable and recommended for Sri Lanka for design speeds less than 70km/h in the context
of safety, but not conservative at lower design speeds in maximizing capacity of two lane
highways.
2017-07-01T00:00:00Z