Article
citation information:
Khabiri, M.M., Afkhamy Meybodi, P.,
Afshari, A. Investigation
and optimisation of a sidewalk restoration program in human transportation
in an ancient sustainable city. Scientific
Journal of Silesian University of Technology. Series Transport. 2020, 109, 61-72. ISSN: 0209-3324. DOI: https://doi.org/10.20858/sjsutst.2020.109.6.
Mohammad Mehdi KHABIRI[1],
Pooya AFKHAMY MEYBODI[2],
Abolfazl AFSHARI[3]
INVESTIGATION
AND OPTIMISATION OF A SIDEWALK RESTORATION PROGRAM IN HUMAN TRANSPORTATION IN
AN ANCIENT SUSTAINABLE CITY
Summary. Sidewalks play a very
important role in the dynamism maintenance as well as the development of cities
especially historic cities. To ensure the maintaining service quality of
sidewalks, the first step is to prevent distress occurrence, thereafter repair
the distress that occurred in the sidewalks. In historic cities, the lack of
suitable sidewalks for walking led to the gradual elimination of pedestrians.
Yazd is a historic city recorded as a world heritage site by UNESCO, which
attracts many tourists from all over the world every year. Therefore,
preserving the quality of sidewalks in this city is of great importance. In
this research, the SCI method was used to investigate the condition of the
sidewalks in the studied area. This method is similar to the pavement condition
index (PCI) method. The results showed that the condition of sidewalks in the
studied area is in the range of 55-70, which is relative.
Keywords: safety, sidewalk pavement, sidewalk condition
index (SCI), maintenance
1. INTRODUCTION
Walking and public transportation are the most
natural, oldest, and most essential forms of human movement in an environment
and are still the most important option for visiting places, activities, and
discovering the values and attractions in the environment [26,28]. Despite the
increasing spread of the use of motor vehicles, walking is still one of the
most important ways of transportation. In this regard, recognising the
effective factors on people’s perception of walking quality can be the
first step for providing a desirable environment for users and promote walking
[5,17].
A sidewalk is one of the road facilities for
pedestrians. The American Association of State Highway and Transportation
Officials (AASHTO) provides the importance and advantages of walking, hence,
sidewalks are considered as significant parts of urban streets [1]. Today,
sidewalk pavements are made of different materials, which were more commonly
used in older areas than traditional materials [19]. The wide use of land in
urban areas such as schools, trade centres, and industrial centres creates high
pedestrians' traffic flows, which should be facilitated by the sidewalks [14].
Increase in the number of pedestrians coupled with limited facilities of a
sidewalk will increase the physical collision between pedestrians and motor
vehicles resulting in increased accidents [6,15,24,29].
Ideally, sidewalks should be capable of meeting the
needs of pedestrians. Therefore, it can be said that good sidewalks are those
that are constructed with the consideration of all groups of users and the
safety assurance of pedestrians [22]. The aim of encouraging walking and
constructing appropriate sidewalks in different cities around the world,
especially in the historic texture, is to the reconstitution of textures.
Achieving this goal prevents historic and old centres of cities from being
empty, attracting tourists and provides opportunities for introducing both
cultural and historical identities. Accordingly, repairing pavements’
distress of streets and roadway is of equal significance as the repairing and
maintaining sidewalks [23]. If designed and maintained appropriately, sidewalks
can provide relatively little displacement costs [10].
All sidewalks need appropriate
maintenance; without maintaining the sidewalks, which are the first encouraging
factor for walking, they can prevent the movement of pedestrians and put them
in the risk of being injured. Thus, to improve the problems pedestrians face,
streets in form of sidewalks should be constructed. These sidewalks increase
public participation and allow pedestrians to enjoy their walk experiences.
Therefore, to satisfy safety and accessibility criteria, sidewalks should have
the following principals: proper size, proper pavement, proper drainage, public
access, safe side access, fantastic spaces, permanent security, and clear signs
and panels [11,12,18,30,31].
The role of civil
infrastructure in architectural and urban development has been widely studied;
therefore, this research aimed to investigate the quality of sidewalks in the
central region of Yazd’s historic city. This region hosts many tourists
every year, and as a result, the quality of its sidewalks and walking cannot be
overlooked.
2.
REQUIREMENTS FOR REGULAR MAINTENANCE OF SIDEWALKS
In
planning for the construction of any type of facility and equipment for
pedestrians, convenience is one of the central factors to be considered. When
walking becomes difficult and complicated for pedestrians, they change their
pass. Sudden path change by pedestrians onto the streets puts them in danger.
If a special age group with different targets use these sidewalks, then
maintenance and repair of these types of sidewalks should be in the top
priority level [25]. The age groups and their characteristics are as follow:
• range of 0-4: movement needs to be under the trained the
supervision of parents. Increase in the environmental vision and perception
depth;
• range of 5-12: increase in the independency, prone to
move fast and getting out of the intersections and entering the streets;
• range of 13-18: feeling invulnerability for entering the
street and passing the intersections;
• range of 19-40: energetic, full awareness of the
surrounding traffic;
• range of 41-65: slow reactions and long reaction time;
• range of >65: difficult pass from the intersections,
low vision and hearing problems [2].
Pavements
are the national wealth of countries, which annually has a significant part of
the development budget of related organisations, including municipalities,
dedicated to their repair, improvement, and maintenance. Supplying enough
credit for these operations is a challenge which managers always face [21].
In
the past, the focus was only on maintaining pavements. Managing pavements was
an unknown determinant factor for choosing the maintenance and repair (M&R)
method has been the experience of the engineers, while little attention was
been paid to lifecycle costs or priority-based network-level requirements. Researches from the beginning of the
1970s in the laboratories of the USA military birthed an engineering management
system (EMS) for paving roads, airports, and parking perimeters known as
pavement management system (PMS) [32]. PMS is a systematic process for
collecting, managing, analysing, concluding and summarising the pavement
information, which is used to support selecting the pavement materials,
maintaining and repairing [7]. In other words, PMS is a planning method for
maintaining and repairing pavements to maximise the pavement life.
PMS
was necessarily inventible given the extent of urban streets inclusive of the
sidewalks in the city, heavy costs of repairmen and the costs exerted on the
users. The pavements’ M&R cost in terms of managing is of great
importance in the PMS system [27]. This system is capable of relative-accurate
estimation of costs need for repairing the damages and passage coating.
Moreover, it provides the managers with optimal solutions for repairing or
coating [20].
Today,
road managers around the world use PMS to define road repair and renovation
strategies. However, to define PMS, some methods and procedures have been
developed on the transportation infrastructures, however, the roads and some
other methods have been defined to calculate the quality level of the sidewalks
[3,4].
One
important feature of PMS is that not only does it have the ability to determine
the existing pavement network status; it is also able to predict its future
status. To obtain a reliable prediction of a pavement status, a repeatable and
visual scoring system should be used [16]. One of these methods is the pavement
condition index (PCI). The PCI is a numerical sign, which is in the range of 0
for a useless pavement to 100 for a flawless pavement [21].
3.
METHODOLOGY AND AREA UNDER STUDY
The
case study was done in the historic texture part of Yazd city in the Amir-
Chakhmaq district. Since it is an area where many tourists annually travel to
from all around Iran and world to visit its rich and ancient monuments, there
is the need to construct distress-free and standard sidewalks to prevent
fatigue on long walks. Alternatively, according to researchers, in
rehabilitation projects of the built heritage, effective communication is
cost-effective by making reliable information available for stakeholders at the
right time. This will help to sustain stakeholders' understanding of project
delivery [9]. Therefore, to summarise the information, numerical indicators are
used to evaluate the infrastructure of cities, especially old cities, as the
condition of sidewalks (SCI).
For
accuracy purposes in the operation of repair and reconstruction, this region
can be divided into smaller parts. On the one hand, according to the location
of the region and the lack of tall buildings with a modern view, and the other
hand, the existence of buildings with low height and traditional view,
constructing an appropriate sidewalk and a safe and convenient environment for
people and tourists is necessary. In these places wherein are trade locations
around the ancient places, there are beautiful landscapes and antiquities
related to the area and location. Among the ancient monuments are Amir-Chakhmaq
square, water museum, and others, which make this region ideal for walking. More
so, it should be noted that according to the region density, traffic accidents
cannot be ignored. These accidents are located in congested areas filled with
vehicles and pedestrians.
Investigating
the region under study, randomly and regularly, the approximate number of
vehicles (about 3000 per day) and the number of pedestrians (about 2000 per
day) can be estimated, which indicates that it is a dense region in terms of
pedestrians. Such factors as the roughness of a sidewalk, presence of trees,
width and quality of the path have a great effect on the number of pedestrians.
The use of the region has changed over time, and the trade centres and stores
have changed to schools or vice versa. The conversion trend of stores to parks
and squares or even cross-sections or conversion of unused spaces to stores or
trade centres have been existing to satisfy the needs of pedestrians. In these
locations, only vehicles on low speeds are allowed to move due to the high
density and volume of pedestrians.
Fig.
1. The path under study (red path)
4.
RESULT AND DISCUSSION
The
condition of a sidewalk is the most important parameter for the maintenance and
repair of the urban pathway. The condition of a sidewalk is measured using SCI,
which is a standard criterion. The Value of SCI indicates the capability of the
sidewalk for servicing the people [13]. SCI was developed in 2014. This index
is similar to PCI, which is defined according to the ASTM D6433 standard. The
condition of the sidewalk is evaluated based on the extent and severity of
damage of the pavement surface [8].
SCI
is conducted via visual inspection by which the type, intensity and extent of
distress are determined. The inspectors identify the number and intensity of
distress based on their checklist. SCI measures two conditions:
1. Type,
extent and intensity of surface distress of the sidewalk (such as cracking and
rutting). 2. Smoothness of the sidewalk surface [2].
The
evaluation and inspection processes are carried out using a systematic method.
The observed evaluations were recorded in a data bank. SCI should be done
annually so that changes in the sidewalk condition can be evaluated [3]. In
addition, SCI recommended strategies necessary for preserving the quality
level, convenience level and safety of sidewalks. SCI is a numerical index,
which defines the current condition of a sidewalk surface. This is an index
criterion, which indicates the structural integration requirements and surface
performance based on the surface distress of the sidewalk. Further, it
determines the roughness location and frictional resistance [2].
Same
as PCI, the SCI range from 0, which indicate the worst condition, and 100 being
the most desirable condition. Table 1 shows this range.
4.1.
Distress of asphalt pavements
Surface
pavements play a significant role in transport, and those in good conditions
provide a safe and easy journey to pedestrians and motorists alike. However,
sidewalk pavements continuously suffer from the combined effects of person and
wheelbarrow loadings and the natural environment. According to the PCI method
and ASTM D6433 standard, the distress of the asphalt pavement can be
categorised as follow:
1) block cracking
2) linear cracking
3) patching and utility cut
patching
4) potholes
5) corrugation
6) swell
7) bleeding
8) weathering/ravelling
9) deformation due to roots
10) deformation due to run-off water
11) differential settlement of the pavement
sub-base layers
12) depressions
13) edge disruption
Tab. 1
SCI
index range [2]
|
Condition
Description |
SCI
Pavement index range |
|
Good |
100 > SCI > 85 |
|
Satisfactory |
85 > SCI > 70 |
|
Fair |
70 > SCI > 55 |
|
Poor |
55 > SCI > 40 |
|
Very
Poor |
40 > SCI > 25 |
|
Serious |
25 > SCI > 10 |
|
Failed |
10 > SCI > 0 |
4.2.
SCI calculation
Like
PCI, the SCI can be obtained from the following equation:
SCI=100
– CDV
(1)
where CDV is the corrected deduct value
considering the relationship between different distress. The CDV equal to zero indicates that the
distress does not affect the sidewalk condition, while the CDV equal to 100 indicate that the distress is highly dangerous.
The CVD is obtained from the
following four steps:
Step
1: determine the density percentage of every type of i in every intensity level:
(2)
where D:
density percentage, Aij:
total area of every distress, i: with
every intensity j (1=low, 2=medium,
and 3= high), Au the area
of every sample unit.
Step 2: calculation of the deduct value (DV) for every distress:
DVij =Pij×Fi
(D%)
(3)
where DVij
is the deduct value, Pij
is the weight dedicated to Fi,
Fi is the value obtained
from the density percentage (D%) for
every distress i. Table 2 lists the
value of the weight dedicated to every distress.
Step 3: calculating the total deduct value (TDV) by summing the values of the
partial deduct value:
(4)
where i is
the number of distress from 1 to 14, j
is the distress intensity (1=low, 2=medium, 3=high).
Step 4: the value of corrected deduct value (CDV):
TDV should be modified to consider the relationship
and correlation of distress. If this correction is not considered, it may round
to very high numbers, which do not indicate the real condition of the pavement.
The correction plots can be obtained by fitting the sum of the deduct value of
all investigated sample units with the values obtained from the pedestrians in
the similar sample units under different conditions. The score values are
varied between zero (worst case) and 10 (best case). Calculations of each
sample unit include mean score with its difference from 10 and the
corresponding value expressed in 100. When the deduct value is less than 10, no
correction is needed. Whereas, when the sum of the correction values is more
than 30 and the sample unit is a distress with density higher than 2%,
then correction is necessary [4]. Fig. 2 shows some of this distress.
In Fig. 3, five
curves are presented for distress Cr from 1 to 5. When Cr=1, no correction is
needed. Table 3 shows an example of calculating the PCI.
|
|
|
|
Fig.
2. Some of the distresses in the region
The PCI of the region
under study is briefly shown in Fig. 4. The green lines have the SCI in the
range of 55-70, indicating relatively good condition. The reason for this is
the timely restoration of this area by the relevant agencies (municipality, cultural
heritage organization, etc.). Conversely, the red lines have SCI in the range
of 40-55, indicating poor condition. This area is located near the unused lands
or near buildings that are under repair. The repairing operation of the
buildings has negative effects on the condition of the sidewalk (such as
settling of the sidewalk, removal of sidewalk pavement due to falling of
objects and/or removal of water pipe path for building). The maximum distress
is for block cracks in the region; however, their intensity is not so much.
Among interviewed pedestrians, the most vulnerable were people with poor
walking ability (people in wheelchairs or kids in wheelchairs).
Fig.
3. The CDV graph [3]
Tab.
2.
Weights
of distress
|
Severity |
Weight |
Distress |
Severity |
Weight |
Distress |
|
Low |
0.3 |
Block Cracking |
Not. |
0.1 |
Deformation Due to Roots |
|
Medium |
0.5 |
Not. |
0.3 |
Deformation Due to Water |
|
|
High |
0.8 |
Not. |
0.6 |
Differential Settlement of the Pavement Sub-Base Layers |
|
|
Low |
0.3 |
Linear Cracking |
Low |
0.8 |
Bleeding |
|
Medium |
0.5 |
Medium |
1.2 |
||
|
High |
0.8 |
High |
0.2 |
||
|
Low |
0.3 |
Patching and Utility Cut Patching |
Low |
0.2 |
Weathering |
|
Medium |
0.5 |
Medium |
0.5 |
||
|
High |
0.9 |
High |
1.1 |
||
|
Low |
0.2 |
Potholes |
Low |
0.1 |
Edge Disruption |
|
Medium |
0.6 |
Medium |
0.3 |
||
|
High |
1.1 |
High |
0.6 |
||
|
Low |
0.3 |
Swell |
|
||
|
Medium |
0.9 |
||||
|
High |
1.2 |
||||
Tab.
3
Example
of SCI calculation
|
Asphalt
pedestrian- condition of sample unit |
|
|||||||||
|
Branch: 1 |
Section: 01 |
Sample unit: 1 |
|
|||||||
|
Sample
area: 120 m2 |
|
|||||||||
|
1- block cracking 2- linear cracking 3- patching and utility cut patching 4- potholes |
5- swell 6- corrugation 7- bleeding 8- ravelling 9- weathering 10 swell |
11- deformation due to run-off water 12- differential settlement of the pavement sub-base layers in
comparison to the interspace of buildings |
13- depressions 14- edge disruption |
|
||||||
|
Type of distress |
Quantity |
Total |
Density (%) |
|
|
|||||
|
1 |
2 |
5 |
3 |
3 |
12 |
10 |
17 |
|||
|
2 |
1 |
2.5 |
3.4 |
3.3 |
10.2 |
8.5 |
18 |
|||
|
4 |
1 |
|
|
|
1 |
0.83 |
54 |
|||
|
5 |
0.5 |
0.5 |
0.6 |
1 |
2.6 |
2.17 |
13.2 |
|||
|
|
TDV = 102.2 CDV = 39 SCI = 61 |
|
||||||||
Fig.
4. General condition of the SCI
(green colour has a relatively good index, and red colour has a weak index)
5.
CONCLUSION
This study is a
primary effort to evaluate the distress condition of sidewalks applying the SCI
approach. This index, like PCI, shows the distress of sidewalks as a value and
provides the range of distress, risks and limitations it creates for pedestrians.
The cases studied investigated sidewalks with asphalt pavement; however, this
method can be similarly applied for sidewalks with concrete pavement.
Although, in this
research, the sidewalks were in relatively good conditions, however, in the
case of lack of appropriate, timely maintenance and repair, the intensity of
distress increases, requiring more cost for repair. According to the results,
the regular planning of maintaining and repair operation does not solely depend
on the distress intensity but equally on the continuity and consistency of pots
and the quality and quantity of pedestrian flow as well. Accordingly, the
experience and method used in this research can help road managers recognise
the maintenance and repair priorities using the SCI method.
Lastly, this study
individually, quantitatively studied the relationships among different distress
types from the statistical view of the sidewalk pavement in a traditional and
ancient city. Researchers are looking for ways to make sidewalks more suitable,
at least for many years. Choosing better quality materials may increase the
cost of project implementation, and reduce maintenance costs over the next few
years.
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Received 23.07.2020; accepted in revised form 01.11.2020
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