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Engineering Approach to
Accident Prevention and
A Downing and H Iskandar
Transport Research Laboratory
Berkshire RG45 6AU
United Kingdom PA3304197 PA33304/97 DOWNING, A and H ISKANDAR (1997).Engineering approach to accident
prevention and reduction. KRT-5, Yogyakarta, 22-24 September, 1997 Republic of Indonesia
Ministry of Public Works
Agency for Research and Development
Isiueof Road Engineering
Road Research Development Project
Published Paper PA 6
TO ACCIDENT PREVENTION & REDUCTION
Paper (Indonesiani version) presented at the 5th Konferensi Regional Teknik Jalan
(KRTJ-5), 2 1-24 September 1997, Yogyakarta, Indonesia.
~ RANS OTT RESERCHTO LABORATORY
Transport Research Laboratory, iil association
United Kingdom. with
PT Yodya Karya,
In don esia.
11 -" ENGINEERING APPROACH
TO ACCIDENT PREVENTION & REDUCTION
List of Contents
1. INTRODUCTION AND OBJECTIVES 1
2. THE MAGNITUDE OF THE ROAD ACCIDENT PROBLEM 2
3 . TOWARDS SAFER ROADS 3
3.1 An Integrated and Scientific Approach 3
3.2 Accident Prevention and Reduction 5
4. ROAD ACCIDENT PREVENTION BY IMPROVED PLANNING
AND DESIGN 5
4.1 Background 5
4.2 .Safe planning of roads 6
4.3 Safe design of roads 12
5. ACCIDENT REDUCTION 1 8
6. EVALUATION OF ROAD SAFETY IMPROVEMENTS 22
7. CONCLUSIONS 24
8. ACKNOWLEDGEMENTS 24
9. REFERENCES 24 ENGINEERING APPROACH
TO ACCIDENT PREVENTION & REDUCTION
A J Downing, Transport Research Laboratory
H Iskandar, Institute of Road Engineering
Although road accidents are usually blamed on road users, it is evident that poor planning
and road design will often have contributed to or compounded these errors. Indonesia, in
common with other rapidly developing countries, has problems with inappropriate
development along highways and outdated design standard. The introduction of modern
accident prevention and reduction approaches should therefore have considerable potential
for saving lives, injuries and property damage in Indonesia.
The Institute of Road Engineering (IRE) has in collaboration with the Transport Research
Laboratory (TRL), UK, initiated the development of a Mficrocomputer Accident Analysis
Package and a black spot investigation and treatment methodology which has been applied
in four trial areas. Also TRL has produced a Guide, Towards Safer Roads, and slide pack
for planners and engineers to encourage both the safe planning and design of new road
(Accident Prevention) and the effective treatment of existing roads (Accident Reduction).
Indon esia has made a sound start but, given the rapid road development, these safety
conscious approaches need to be adopted nationwide before it is too late.
This paper outlines some of the key principles of the TRI, Guide. For example, land use
planning and zoning to reduce travel and exposure of vulnerable groups to traffic, restricted
access to arterial roads and avoidance of ribbon development, the establishment of road
hierarchies with real functional and design differences, the provision of safe facilities for
vulnerable road users, improved delineation and control of overtaking and speed. The
principles are supported with examples and some evidence from case studies from
Indonesia and South East Asia.
1. INTRODUCTION AND OBJECTIVES
Studies of police road accident records show that, in all countries, the police typically
identify the main cause of road accidents as human error. Indonesia is no exception with
most of the accidents in 1995 being attributed to human error, and very few to road
problems. Does this means engineers have no role to play in road safety ? No, far from It;,
in many motorised countries engineers have led the attack on road accidents with
outstanding success. Why then should engineers play a leading role in road safety ? There
are four key reasons as follows.
1). Inconsistencies and complexities in the road design and road network will
significantly increase the difficulty of the road users' tasks and result in more road
1 Cstfi.Krtj-5h.wpd25.06.97 2). Inappropriate planning of the road network in relation to land use and road function
will unnecessarily expose road users, particularly the vulnerable, to the risk of road
3). Research in many countries (Downing, 1997) has shown that road planning, design
and engineering countermeasures can lead to significant accident reductions and
provide a more forgiving environment thus reducing the severity of injuries.
4). Road engineering improvements are relatively straightforward to implement and
they usually have an immediate effect.
Generally, road planners and engineers in the highly motorised countries have learnt from
the mistakes made in the past and realised the potential of road safety conscious planning
and design. However, most of their counterparts in developing countries are often still
preoccupied with the problems of road construction and maintenance and increasing the
network capacity. Thus, all too frequently, roads and road systems are being built or
upgraded with little consideration given to road safety. As a result 'black spots' and 'black
links' are created and many road users are being killed or injured unnecessarily. Therefore,
the purpose of this paper is to bring road safety to the forefront of the minds of planners and
engineers and to give examples of the key safety principles of accident prevention and
The paper highlights the magnitude of the road accident problem in Indonesia and
summarises some of the key principles from two key manuals ie the Transport Research
Laboratory's (TRL, 199 1) "Towards Safer Roads in Developing Countries" and from the
"Interim Manual on Accident Investigation Procedures and the Development of Low-Cost
Engineering Improvement Schemes" produced jointly by Pusat Litbang Jalan (lIRE) and
TRL (TRL/IR.E, 1993).
It is important that these principles and approaches are verified in Indonesia conditions and
the paper concludes with a review of the results of some road safety studies in the South
East Asian region.
2. THE MAGNITUDE OF THE ROAD ACCIDENT PROBLEM
The reported road accident statistics from the Indonesian Traffic Police Headquarters are
shown in Table 1 together with vehicle data and an estimate for the 1995 casualties
allowing for under-reporting of accidents by the public.
From the table it is clear that vehicle registrations have increased by over 70 per cent from
1986 to 1995 whereas reported accidents have declined by 60 per cent, thus the accident
rate has dropped forom 57 in 1986 to only 13 in 1995. The fatality rate has also declined but
much more slowly than the accident rate and numbers of deaths have remained fairly stable
with 1994 and 1995 having the highest figures in the last ten years.
These figures overall look promising but there are two worrying features ie 1) the number
of casualties per reported accident increased steadily from 1986 to 1993 and 2) the fatality
index or the percentage of casualties who die in road accidents has increased steadily over
2 Csfi.Krtj-5b.wpd25.06.97 the last 10 years to a level which is nearly double that of ten years ago. These trends
indicate that the accidents reported to the police are becoming more serious. This findin
may reflect a real change in Indonesia, for example there may be an increase in the
involvement of public service vehicles in accidents or vehicle occupancy levels may be
increasing with a corresponding increase in passengers killed or injured. Alternatively, and
this seems more likely, there may be a change in the public's accident reporting behaviour
with an increasing tendency to report only the most serious accidents. Under reporting is
clearly a characteristic of the road accident statistics in Indonesia and even deaths from road
accidents are under estimated as the statistics are not updated for victims who die after they
have been removed from the scene of the accident.
The Hlighway Capacity Manual Project (SweRoad/Bina Marga, 1995) attempted to estimate
the real magnitude of the problem in Indonesia using typical ratio's of Fatalities to other
seventies of casualties based on Swedish experience. It was assumed that the minimum
increase in fatalities was 50 per cent (similar to the Indonesia insurance claim statistics) and
then other casualties were calculated using multipliers of the number of deaths. In Table
I the same approach was used but the multipliers were based on those which applied to the
UK in 1927 as these give a more conservative estimate of the number of casualties in
relation to deaths. With these figures there were an estimated 478,065 casualties in
Indonesia in 1995 compared with only 32,804 reported to the police le 93 per cent of the
casualties are missing from the national statistics. This figure must be treated with caution
and research is needed to compare hospital and medical cases with police cases to obtain
a more reliable estimate of the real problem. Nevertheless the national statistics, even
without correction, show a very serious problem as regards the fatality rate which is more
than six times higher than that of the UK (see Table 1).
3. TOWARD SAFER ROADS
3.1 An Integrated and Scientific Approach
It widely recognised that road safety is the responsibility of many sectors and that an
integrated approach to national and local action is required. Remedial action is usually
grouped under the 3 E's ie engineering, education and enforcement with additional
concepts also recommended such as evaluation and encouragement.
In order to successfully implement a multi-disciplinary action programme, a number of key
requirements need to be met. The most important are:
1). A reliable and valid national road accident database
2). A national road safety plan based on a scientific and rational diagnosis of the road
3). National and local coordinating agencies with the necessary authority and resources
to implement the plan.
4). Professional staff trained in the latest road safety approaches and technology.
5). Evaluation of the measures with feedback to the national plan.
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0~ Indonesia has taken a number of positive steps to reduce the road accident problem, for
example there is a National Road Safety Plan and an improved accident information system
known as Triple-L. Also the traffic law has been revised and trial black spot treatments
introduced with evaluation carried out by Pusat Litbang Jalan (IRE).
However there are still many potentially, highly effective measures and improvements for
Indonesia to implement. Of course, care needs to be taken with the transfer of technology
from one region of the world to another, but in the case of strategies and approaches to
managing road safety, it is likely that these are applicable worldwide. Individual
countermeasures or treatments on the other hand need to be appropriate for local conditions
and integrated with other actions particularly publicity and possibly enforcement if they are
to be successful.
3.2 Accident Prevention and Reduction
An important road safety concept is the distinction between Accident Prevention and
Accident Prevention involves improved planning and design of new roads and related
developments to minimise road accidents and casualties. Not only are schemes designed
wihsafety in mind but also they are checked by impartial safety specialists (road safety
audit) to ensure that safety considerations have been met.
Accident Reduction involves the application of cost effective measures to the existing road
network particularly those sites, sections or areas with known accident problems.
To encourage developing countries take up these approaches the Transport Research
Laboratory (TRL) in collaboration with the Ross Silcock Partnership, developed a guide
for planners and engineers (TRL/Ross Silcock, 1991) and a slide pack (TRL/Ross Silcock,
1994). Also the TRL, in collaboration with lIRE, produced an interim manual on the
development of low-cost engineering improvement schemes (TRL/IRE, 1993) in order that
a systematic approach for reducing road accidents at hazardous locations could be
introduced in Indonesia. The next two sections of this paper summarise the key principles
of these two manuals with examples. There are many other useful publications for road
safety professionals and a selection of these is listed in the reference section of this paper.
4. ROAD ACCIDENT PREVENTION BY IMCROVED PLANNING & DESIGN
The Government of Indonesia is committed to major investment in expanding the road
network and providing safe and efficient roads for the general public. It is therefore
essential that safe planning and design practices are adopted. Table 2 shows some of the
key characteristics of accidents found in 4 areas of Java (IRE, 1997).
C:Rsztfelfii. Krtj-5b.wpd25.06.97 5 Table 2 Key characteristics of accidents in Java, 1993-95
The planning and design improvements should focus on reducing the main accident
problems. From the Table, priority needs to be given to improving the safety of
motorcyclists, pedestrians and buses particularly in areas of residential development both
on urban and rural roads. The percentage of accidents occurring on rural roads with
resdential land use is exceptionally high but not surprising given the ribbon development
prevalent in Java. Indonesia's expansion of its road network provides an ideal opportunities
to introduce safer planning and design practices. Some important strategies which need to
be adopted are:.
1). Match the function, design and use of roads and classify roads into a hierarchy.
2). Provide road designs and environments which guide and match road user
3). Manage speed and keep speed below 30 kph where pedestrians share the road space
4). Control access and development to minimise high risk manoeuvres and exposure
of vulnerable road users.
5). Provide a road environment which is forgiving and tolerant of human error.
6). Check schemes for safety at the various design and completion stages (safety audit)
and modify as necessary.
The "Towards Safer Roads" manual contains many principles, recommendations and
examples and, given the space and time restrictions of this paper, only those most relevant
to the Indonesian situation have been selected and described below.
4.2 Safe planning of roads
The five priority components of safe planning are as follows.
I). Road Hierarchy. The roads in a network should be clearly defined and classified
into those which are primarily for movement (through traffic) and those which are
primariily for local access. Some key principles are:
6 Csf fnKrj.j5b.wpd25.06.97
Percentage of casualties of
Casualty/Accident Characteristic accidents
_______________________________ Urban Rural
1. Casualties were: 1). Motorcyclists 40 25
2). Pedestrians 25 14
3). From buses/minibus 12 33
2. Accidents occurred: 1). Away from junctions 77 93
2). In residential areas or villages 65 89
3. Collisions were: 1). Head on 19 42
2). Side swipe 26 10
________ _______ _______ 3). N ote to tail 21 17
Table 2 o Network hierarchy aids Development Control
o Hierarchical levels assigned on intended or desired and not historical
o Networks should create self contained zones to exclude extraneous traffic
o Natural barrier effects of main routes can be used to segregate/contain
o Appearance and design standards should clearly convey role of road and
include appropriate speeds of traffic
o Existing grid network layouts can be modified to hierarchical networks
o Numbers, type and spacing of intersections should be consistent with
o Roads should intersect only with roads in same level or one level higher or
lower in the hierarchy
An example of an ideal hierarchy is shown in Figure 1.
Figure 1 Ideal road hierarchy
2). Land use. Land-uses should be organised and controlled to minimise traffic and
pedestrian conflicts and reduce the need for travel. Ideally people's work needs and
shopping requirements should be located within safe walking distance of their
homes. The key principles are:
Control of land-use and traffic is vital
Segregate incompatible uses
Design networks to minimise conflicts
Plan land-use to minimise travel and maximise accessibility to public
7 C:R~sif'en. Kitj-5b.wj
An example of unsafe and safer land use is shown in Figure 2 and the importance
of development control in Figure 3.
.q ' .... .....
Figure 2 Land use to minimise pedestrian conflicts
Figure 3 Development control
-A')n nA 07 ~~~~8 3). Access Control. Direct frontage or access onto major roads or near intersections
should be minimised and not permitted at all at dangerous locations such as bends
or hill crests.
o Number of intersections should be minimised, junctions simplified and
service roads provided
o Traffic should work up through hierarchy of roads to reach primary road
o Priority should always be given to road higher in hierarchy. All minor roads
to have stop or give way marking/signs where they meet major road
o Highway authorities must introduce control system which requires
developers to get permission when they wish to access onto public roads
o Small full-time development control team needed to assess/review access
proposals -must have powers to enforce closures and remove illegal
o Access roads to parking areas of major facilities (hospitals, shopping
centres etc) to be at least 50m from junctions
An example of good and poor access control is shown in Figure 4.
Figure 4 Access Control
4). Arterial Roads. Capacity expansion and rehabilitation projects must consider the
existing usage of the road and ensure that the local user's needs and safety are
maintained. The key principles are:
C:Rskfen. Krtj-5b wpd25.06.97 9 Where bypasses can be justified
o Downgrade old road to discourage through traffic, reduce speeds
and reinforce hierarchy
o Provide only a few links from old road to new road, preferably via
o Prohibit direct access from adjacent frontage land onto new road
o Leave provision for future expansion of community but serve via
2. Where bypasses cannot be justified
o Slow down through traffic speeds as it passes through community
o Examples of techniques:
- advance warning signs and rumble strips to warn of speed
reducing devices ahead
- chicanes, road narrowing or road humps to slow traffic
where pedestrians predominate; and refuges where necessary
- "gates" such as chicanes or road narrowing to alert drivers
that they are entering low speed area
o Provide urban high speed road along existing alignment only if
separate service roads, restricted access, and grade separated
pedestrian crossing facilities can be provided.
The importance of speed control on arterial roads especially interurban roads
passing through towns or villages cannot be underemphasised. An example of this
type of problem is shown in Figure 5.
Figure 5 Arterial roads
10 C:Rs~tieii. Krtj-5b.wpd25.06.97 Figure 6 Speed reductions
5). Access and residential roads. Access roads should aim to provide a safe and
comfortable environment for the local community particularly for the vulnerable
road users. The key principles are:
o0 Access roads should have safety, security, social and environmental issues
as primary concerns
o This can be brought about as follows:
- vehicle flows minimised and unnecessary traffic eliminated
- vehicle speeds kept low through appropriate design eg roads short