Survey and Design Consistency Evaluation in Two-Lane Rural Road
Segments
PANAGIOTIS LEMONAKIS, GEORGE KOURKOUMPAS,
GEORGE KALIABETSOS, NIKOLAOS ELIOU
Department of Civil Engineering, Section of Transportation, University of Thessaly,
Pedion Areos, 38334 Volos, GREECE
Abstract: - The present research proposes a time and cost-effective methodology to survey and perform a design
consistency evaluation in two-lane rural road segments. The implementation of the proposed methodology carried
out in Central Greece and more particularly along the national road Volos-Karditsa, from the local community
Mikrothives up to the entrance of the Volos municipal unit. The road survey methodology, the process of creating
the terrain model as well as the cross-check between the designed road with the requirements included in the
Greek Road Design Guidelines Manual-Chapter X, are analytically presented. Similar checks are also performed
for the sight distance throughout the road segments aiming to enable the rehabilitation of existing rural roads and
enhance their safety level.
The design of the road was followed by the execution of an experiment with the participation of a motorcycle
rider aiming at the recording of his trajectory throughout the road which was then compared with its geometry.
The experiment carried out by exploiting an instrumented vehicle and GPS technology. Several conclusions were
drawn regarding the encroachment of the centerline and the deviation from the theoretical trajectory in the middle
of the travelled way. Subsequently, the proposed methodology provides a reliable and simple solution of
surveying and evaluating a 2-lane rural road in safety terms.
Key-Words: - Design consistency, GPS, road safety, rural road survey.
Received: March 17, 2021. Revised: October 26, 2021. Accepted: December 19, 2021. Published: January 9, 2022.
1 Introduction
The primary objects of the present research were to
propose a road surveying method for the assessment of
road alignments on the one hand and to inspect whether an
existing two-lane rural road meets certain safety criteria on
the other hand. The methodology that was followed to
design the terrain model is presented in detail whereas at
the end of the research the proposed methodology is
evaluated through a case study. The safety requirements
are derived from the Greek Road Design Guidelines
Manual [1] which determines the safety criteria upon
which a road is evaluated. The ultimate aim of the present
research is to introduce a cost and time-effective method
to specify the road segments that need to be upgraded and
reach an acceptable safety level.
The widespread practice of road surveying methods is
the development of digital terrain models, based on known
terrain coordinates in the three-axis system. These
coordinates are used to generate the digital terrain model
exploiting the triangulation method. The generated digital
terrains can be used thereafter in many sophisticated road
design software such as Anadelta Tessera (used in the
present research), ΟΔΟΣ V8, Diolkos3d, etc [2, 3].
Various attempts to develop a comprehensive
methodology to evaluate the safety level of existing road
segments have been documented in the past. The first step
in all of them was the digital survey of the vertical and
horizontal alignment of a road. The first documented
attempt was by Psarianos et al in 2001 [4] who managed
to survey and calculate the alignment of 1.300 km of the
national road network in Greece. The outcome of the study
was the development of the Hellas Road Software which
required the use of a GPS receiver, a pc, an inclinometer,
three cameras and, an instrumented light truck, and
provided particularly accurate road alignments.
Another relevant study was conducted at the National
Technical University of Athens in which Software H12
was developed [5]. The imported data to H12 are only the
x,y,z coordinates of the axis of the road segment. Through
the software, the angular and azimuth diagrams of the road
are calculated which form the basis for the design of the
horizontal and vertical alignment of the road. Another
research that was conducted in the same University used
the topographic survey method to investigate the
trajectories of cars along horizontal curves [6]. Although
this method offers a high degree of accuracy, it is non-cost
and time-effective.
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Panagiotis Lemonakis, George Kourkoumpas,
George Kaliabetsos, Nikolaos Eliou
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An alternative approach to identify the alignments of
existing roads used the recorded data from a GPS device
throughout the borderlines of the road [7]. The geometry
of each borderline individually was automatically
calculated through an algorithm that was compiled on
FORTRAN programming language. The efficiency of the
proposed methodology was tested in two road segments
with satisfactory results.
At a later stage, the aforementioned algorithm was
improved by joining arcs of the same direction with small
tangents in between. The outcome was the assessment of a
more accurate road alignment [8]. The tests at the same
road segments confirmed that the updated algorithm
provides better alignments.
2 Methodology
The study area is located at the prefecture of Magnesia
near to Volos – Greece. It has a length of approximately
17.100 m and belongs to the AIII type of road as defined
in the Greek Road Design Guidelines Manual Chapter 1
[9]. The starting point is the end of I/C Mikrothives of the
Athens – Thessaloniki motorway. The terrain up to Nea
Achialos municipal is plain with smooth differences in
altitude whereas on the contrary the road segment after
Nea Achialos traverses a hilly terrain where multiple
horizontal curves lie (Fig. 1).
Fig. 1: Sketch of the rural 2-lane road [10]
2.1 Surveying method
The instrument that was used to survey the borderlines
of the road segment considered was the Global Navigation
Satellite System (GNSS) receiver Stonex S9 III (Fig. 2).
The GNSS receiver was connected to the CivilShop
networks of continuously operating reference stations
[11]. The recording equipment uses the Greek Geodetic
Reference System 87.
Fig. 2: Survey GPS Stonex S9 III on vehicle [10]
The accuracy of the measurements was as follows:
• Horizontal Axis x-y (plane): 0,02 m.
• Vertical Axis z (elevation from sea level): 0,05 m.
• Recording rate: 1 Hz.
The trajectory of the instrumented vehicle was as close
as possible to the right borderline whereas throughout the
operation its speed was less than 20 km/h. These settings
combined with the geometric features of the road segment
resulted in 5.069 recorded points for both borderlines of
the road.
2.2 Generation of the Terrain Model
The first step to generate the terrain model was to import
the recorded data (ground profile data) from the GNSS
receiver into software Anadelta Tessera which
automatically generates a terrain model from the raw data.
A preview of the imported data is presented on Fig. 3 (a)
whereas on Fig. 3 (b) a series of recorded points on a
random segment for both borderlines is depicted.
(a)
(b)
Fig. 3: Import of borderlines points [10]
A more detailed examination of Fig. 3 revealed
inconsistencies on the recorded data either due to
temporary loss of signal between the GNSS and GPS or
due to various obstacles that were lying on the right side
of the pavement rendering the movement of the
instrumented vehicle above them impossible (e.g. parked
cars, trash bins). Attempting to overcome this finding, an
approximate calculation of the terrain points at the
inconsistent segments performed aiming to achieve a
better illustration of both the horizontal alignment as well
as to the terrain model. More precisely, various points were
imported throughout the inconsistent segments. The
altitude of these points was calculated by implementing
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Panagiotis Lemonakis, George Kourkoumpas,
George Kaliabetsos, Nikolaos Eliou
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linear interpolation between the points that were preceding
and following the new ones. At the next stage, all points
are joined to form a united database, and finally, the
triangulation method implemented.
With this procedure the terrain model of the existing
road developed, which was then used as the fundamental
element to proceed to the design of the road alignment. The
similar procedure implemented to calculate a second
terrain model along to the study area using terrain points
from Google Earth. The latter model permitted the
illustration of the terrain beyond the borderlines of the
road.
2.3 Road Design
The terrain model as calculated by the terrain points that
were recorded with the GNSS receiver was used to design
the alignment of the road. That was accomplished by a
supervised/graphical method through an appropriate
software (Anadelta Tessera) by taking the borderlines of
the road as granted. The result was the design of the axis
of the road segment as a sequence of joined straight lines
and arcs (Fig. 4).
Fig. 4: Original road alignment [10]
The ultimate stage of the horizontal design of the road
was to insert the clothoids at the beginning and end of each
horizontal curve. That was also accomplished with a
similar supervised/graphical method by adjusting the value
of parameter A of the clothoid to fit the terrain model (Fig.
5).
Fig. 5: Final road alignment [10]
Τhe terrain model together with the horizontal
alignment were the two prerequisites to design the vertical
alignment, the cross-section, and the superelevation
diagram of the road (Fig. 6). That was performed through
the design software which offers the possibility to
automatically generate the vertical alignment of the
surveyed road segment, once the horizontal alignment has
been finalized. The vertical alignment and the cross-
sections are also automatically regenerated after any
changes occur to the horizontal alignment.
Fig. 6: Vertical alignment – Axis of GPS points [10]
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Panagiotis Lemonakis, George Kourkoumpas,
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The design of the longitudinal profile was also
performed with the implementation of the
supervised/graphical method. Particular attention was
given to ensure that the road centreline vertical alignment
along tangents was approximately +0.10 m above the
ground vertical alignment derived from the recorded
ground profile data. This limit was set because the
recorded ground profile data refer to the borderline instead
of the axis of the road. Therefore, it was deemed that in the
tangent segments the difference between the centreline and
both borderlines of the road was approximately +0.10 m.
On the contrary along the curves, efforts were put to ensure
that the elevation of the centreline and the elevation of the
ground digital elevation model were identical.
3 Results
3.1 Safety criteria
The next step of the research was the evaluation of the
road segment from the first two safety criteria determined
in the Greek Road Design Guidelines Manual-Chapter X
[1] i.e. design consistency according to the design speed
and design consistency according to the operational speed
V85. The original design of the road was not available and
hence the value of the design speed, a necessary
component to evaluate the first safety criteria, was not
known. To overcome this shortcoming, the design speed
was set as the mean value of the operational speed V85. It
must be noted that the various operating speeds were
calculated automatically using suitable software and
therefore the calculation of their mean speed was
effortless. More specifically the mean value of the
operational speed was 87 km/h and hence the design speed
Ve was approximately chosen equal to 80 km/h. The
calculation of the difference |V85 - Ve| for the consecutive
road segments was then feasible.
According to the first safety criterion the design of an
existing road is classified according to the following
conditions, depending on the value of the afore-mentioned
difference:
• less than 10 km/h “good”
• between 10 km/h and 20 km/h “moderate”
• more than 20 km/h “poor” (redesign is
mandatory)
In this way, the road segments were sorted based on the
value of the corresponding V85. The implementation of the
first criterion to the road under investigation disclosed that
its design consistency is rather “moderate”.
Taking the operational speeds of the road as granted the
next step was to implement the second safety criterion
which compares the differences |V85i – V85i+1|, between the
consecutive road elements. A road element is either a
straight line (tangent) or a curve section of the form entry
clothoid-circular curve- exit clothoid. The conditions that
should be met to decide whether two consecutive road
elements are considered optimum, moderate, or not
acceptable are similar to the first criterion. According to
the second criterion and by considering the individual
scores between the consecutive road elements the road
under investigation is classified as “good”.
3.2 Sight distance
To enhance traffic safety as well as the quality of the
traffic flow, minimum sight distances must be ensured.
From this perspective the road users will be alerted on time
for potential threats on the pavement (stopping sight
distance), an adequate distance for overtaking will be
available (sight distance for overtaking) and the drivers
can exploit more time to change their trajectory if needed
(sight distance for decision making).
Through the design software the sight distance for
specific road segments that met certain requirements e.g.
sharp horizontal curves combined with convex crest curve,
was calculated (Fig. 7).
Fig. 7: Example of sight distance [10]
The data to accomplish this task was obtained from
Google Earth [12]. Initially, the paths that circumscribe the
road under investigation were plotted (Fig. 8) by joining
the scattered 2-dimensional points. Subsequently, in each
one of the plotted points, an altitude was assigned through
the online project GPS Visualizer which derives altitude
data from NASA’s database [13].
Fig. 8: Generation of path points [10]
This new model constituted the basis on which the road
that was produced at the first stage merged. As presented
in Table 1 the road designed with the procedure described
before is particularly accurate.
WSEAS TRANSACTIONS on SYSTEMS and CONTROL
DOI: 10.37394/23203.2022.17.6
Panagiotis Lemonakis, George Kourkoumpas,
George Kaliabetsos, Nikolaos Eliou
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Table 1: Average – Mean deviation – Mean standard
deviation
Average
altitude
difference (Axis
altitude
ANADELTA-
Axis altitude
GPS)
Mean
deviation
(Altitude
difference -
Average)
Mikrothives -
Volos
0.0165
0.0709
Mikrothives -
Anchialos
-0.0029
0.0612
Anchialos -
Volos
0.0293
0.0799
On the contrary, the terrain model did not accord with
reality. Altitude deviations of 2-3 meters were identified
which is considered as an acceptable error.
4 Conclusions
The subject of the present research was, on the one hand,
the introduction of a reliable and practical methodology of
surveying an existing road whereas on the other hand the
evaluation of the road geometry according to the first two
criteria mentioned in the Greek Road Design Guidelines
Manual-Chapter X and to the adequacy of sight distance.
The procedure that has been implemented so far to survey
and evaluate the road segments in safety terms is time and
cost consuming since it requires the use of specialized
equipment and sophisticated software. Moreover, the use
of GPS technology to calculate the boundary lines of the
various road sections lacks accuracy since the GPS only
offers a 3 m position accuracy. Therefore, it provides
horizontal and vertical alignments which do not imprint
the actual road. On the other hand, the proposed
methodology is not only cost but also time effective
because it utilizes freeware software and a relatively
inexpensive device. These benefits renders it an ideal
solution for both professional and educational purposes.
The next steps might include the evaluation of the road
based on the requirements of the German (RAA) [14] or
the American Guidelines [15]. Therefore, the methodology
described before provides a reliable, easy, and cost-
effective tool to survey and evaluate not only existing road
segments but also preliminary road designs.
References
[1]
Ministry of Environment Regional Plannin
g and Public Projects, Guidelines for the
Design of Road Infrastructure Projects -
Designs, Chapter 3: General Secretariat of
Public Works, 2001.
[2]
Anadelta Tessera,
"http://www.anadelta.com/index-
gr.php?s=tessera," [Online].
[3]
Diolkos3d, "https://www.diolkos3d.com/,"
[Online].
[4]
B. Psarianos, D. Paradisis, B. Nakos and G.
Karras, "A cost-effective road surveying
method for the assessment of road
alignments," in IV International Symposium
Turkish-German Joint Geodetic Days,
Berlin, 2001.
[5]
Vasilas, Development of an algorithm to
digitaly design an existing road, Athens,
Greece: National Technical University of
Athens, Thesis, 2013.
[6]
E. Siora, Investigation of the real curvature
of the vehicle's trajectory concerning the
design curvature of two-lane rural roads,
Athens, Greece: National Technical
University of Athens, Thesis, 2009.
[7]
N. Eliou, G. Kaliabetsos, G. Karaoglanis
and A. Galanis, "Development of and
algorith to identify the geometry of an
existing road," in 6h Panhellenic
Conference on Road Safety, Athens, 2015.
[8]
Papadopoulos, Algorithm to identify the
geometry of an existing road, Volos,
Greece: University of Thessaly, Thesis,
2017.
[9]
Ministry of Environment Regional Planning
and Public Projects, Guidelines for the
Design of Road Infrastructure Projects -
Operational Classification of Road
Network, Chapter 1: General Secretariat of
Public Works, 2001.
[10]
G. Kourkoubas, Survey and check of the
geometrical features of an existing road,
Volos, Greece: University of Thessaly,
Thesis, 2018.
[11]
CivilShop, "http://www.civilshop.gr/,"
[Online].
[12]
Google Earth,
"https://www.google.com/earth/," [Online].
[13]
S. T. NASA,
"https://www2.jpl.nasa.gov/srtm/,"
[Online].
[14]
M. Rohloff, Richtlinien für die Anlage von
Autobahnen (Guidelines for the design of
motorways), FGSV, R1, Regelwerk., 202:
Kln : FGSV-Verl., 2008.
[15]
AASHTO, Policy on Geometric Design of
Highways and Streets, 6th Edition:
American Association of State Highway and
Transportation Officials, 2011.
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Panagiotis Lemonakis, George Kourkoumpas,
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Contribution of individual authors to
the creation of a scientific article
(ghostwriting policy)
Panagiotis Lemonakis contributed to all steps of the
present study and particularly he organized, executed
and, analyzed the field measurements.
George Kourkoumpas was responsible for the set up
of the field measurements and the post statistical
analysis.
George Kaliabetsos contributed to the literature
review of the study and the post analysis of the
recorded data.
Nikolaos Eliou assisted in the recruitment and
execution of the field measurements presented in
section 2.1 and the interpretation of the results.
Sources of funding for research
presented in a scientific article or
scientific article itself
This research study was conducted under the post-
doc scholarship supported by the University of
Thessaly and exclusively funded by Stavros Niarchos
Foundation.
Creative Commons Attribution
License 4.0 (Attribution 4.0
International, CC BY 4.0)
This article is published under the terms of the
Creative Commons Attribution License 4.0
https://creativecommons.org/licenses/by/4.0/deed.en
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WSEAS TRANSACTIONS on SYSTEMS and CONTROL
DOI: 10.37394/23203.2022.17.6
Panagiotis Lemonakis, George Kourkoumpas,
George Kaliabetsos, Nikolaos Eliou
E-ISSN: 2224-2856
55
Volume 17, 2022