benefit-cost analysis of roundabouts in a ......benefit-cost analysis of roundabouts in a brazilian...

Benefit-cost analysis of roundabouts in a Brazilian city regarding to the number and severity of traffic accidents – A case of study

BEZERRA, Barbara S.; ROMÃO, Magaly P.V; FERRAZ, Antonio C. P.

12th WCTR, July 11-15, 2010 – Lisbon, Portugal

1

BENEFIT-COST ANALYSIS OF ROUNDABOUTS IN A BRAZILIAN CITY

REGARDING TO THE NUMBER AND SEVERITY OF TRAFFIC ACCIDENTS – A

CASE STUDY

Barbara Stolte Bezerra, Universidade de São Paulo, Departamento de Transportes, Av. Trabalhador Sãocarlense 400, São Carlos/SP, [email protected]

Magaly P. Vasconcellos Romão, Universidade de São Paulo, Departamento de Transportes, Av. Trabalhador Sãocarlense 400, São Carlos/SP, [email protected]

Antonio Clóvis Pinto Ferraz Universidade de São Paulo, Departamento de Transportes, Av. Trabalhador Sãocarlense 400, São Carlos/SP, [email protected]

ABSTRACT

This paper has the objective to analyze the benefit-cost of building roundabouts as a traffic

safety infrastructure measure in Jaú city, Brazil. The chosen places have priority over other

intersections because they have data available to analyze the before-after situation. Jaú city

has the database with information from 2000 until 2007, as well as the dates of construction’s

implementation. It was made a research on the accident database of the Jaú Secretary of

Transport. After this research, the cost-benefit analysis was calculated using a methodology

described by Hauer (1997). The percentage of reduction in the number of accidents found in

this study is in accordance which is founded in the literature, around 50% of reduction in

accidents and severity (Várhely, 1996). In contradiction, other studies founded that the

introduction of roundabouts reduces the severity of accidents, but increase the number of

property damage accidents until 73% (Elvik and Vaa, 2004). In this study of case was found

that the number of property damage accidents and severity of accidents were reduced with

roundabouts. However, some disclaimers must be made with these results: it was used the

naive before-after studies approach, so the percentages of reduction could be related to

other factors not only to roundabouts, the vehicle flow was not considered, and as the sites

was chosen due the high rates of conflicts which could have bring bias to the sample.

Keywords: roundabout, traffic safety, benefit- cost




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1. INTRODUCTION

The road accidents are a serious problem in the contemporary world. WHO (2004) estimated

that in 2002 occurred 1,180,000 deaths because road accidents (average of 3242 deaths per

day) and around 20 to 50 millions of injured people, whom many of them with physical and

mental incapacity or severe psychology sequel, which prevent normal life.

This scenario will be more tragic in the future if adequate polices would not took in practice,

because the forecast is that this number will be raise reaching the milestone of 2 million of

death in the year of 2020. This estimative consider an increase of 80% of death in not

developed countries and a reduction of 30% in developed countries (this countries are

undertaken efficient actions to reduce deaths and accidents in traffic).

The road accidents were 11th cause of deaths in the world in 2002 (around 2.1% of total). In

the group of people between 5 and 40 years old, was the 2nd cause of deaths. In the year of

2020, the forecast is that road accidents will be the 6th cause, with 3.4% of total of deaths.

However, as the victims (dead and injured) in traffic are more frequent among young people,

the most suitable healthy indicator of impacts of road accidents to society is DALY (Disability-

Adjust Life Year): a measure that combine the number of years lost due to premature death

and the number of years lived with the disability (weighted accordingly to the type of

disability). With this indicator, in 1990, the road accidents were classified in the 9th position,

being responsible for approximately 2.6% of total sum of all Daly’s indicators. In 2020, the

forecast is that road accidents will be in 3th position, behind only by heath disease and

depression, being 5.15% of total sum of all Daly’s indicators. Considering only the countries

with medium and low developing, the road accidents will occupy in 2020 the 2nd position,

behind only by heath disease.

1.1. BRAZILIAN SCENARIO

In Brazil, according to OEI (2007), MS (2006) and ABRAMET (2007), the follows annual

numbers of road accidents for the year of 2005 were: 1 million of accidents, 385 thousands

accidents with victims (82% in urban areas, and 18% in rural areas), 36 thousands deaths,

515 thousands injured (with 100 thousands with permanent disability), 208 accidents with

victims per 100 thousand inhabitants, 91 accidents with victims per 10 thousand vehicles,

279 victims per 100 thousand inhabitants, 122 victims per 10 thousand vehicles, 19 deaths

per 100 thousand inhabitants and 85 deaths per 10 thousand vehicles.

The comparison of index of mortality in traffic in Brazil with developed countries shows the

seriousness of the road accidents in the Country. The relation between the number of deaths

and vehicle fleet is, in Brazil, more than 10 times superior than Switzerland, Sweden and

Japan: more than 8 times superior than Germany and Great Britain; 5 times superior than

France, Canada; and 4 times superior United States.




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This dramatic situation tend to worse furthermore, considering that the number of deaths in

traffic turn to raise since 2001, after experiencing a decline in the years 1998, 1999 and

2000, due to the implementation of the new Brazilian Traffic Law (Law nº 9.503, published in

23/09/1997).

The deaths rates associated to different causes of mortality confirm the seriousness of road

accidents in Brazil. Considering the top ten causes of deaths in the year of 2004, the road

accidents are in 7th position, with a rate of 19.6 deaths per 100 thousands inhabitants. The

other aspect extremely negative of road accidents is the impact that they have over the

economy. By WHO (2004), the monetary cost of injured and deaths in traffic around the

world in 2002 was estimated in 518 billions of dollars. In this estimative, were considering the

follows percentages in the GDP for the cost of road accidents: 1% in countries with low

developing; 1.5% in countries with medium developing and 2% in developing countries.

In this total, are included the following costs: hospital, treatment and rehabilitation of the

victims, material lost (vehicles, goods, road furniture, etc.); removing crashed vehicles,

rescue of victims, clean and repair of damages caused on the road environment, lost of labor

days, pensions and early retirements, police and litigation costs, etc.

Based on the studies of IPEA (2003), about road accidents in urban areas, and IPEA (2006),

about road accidents in rural areas, the annual cost of road accidents in Brazil is estimated to

be around 21 billions of dollars, which correspond to 1.24% of Brazilian GDP in 2007,

approximately. This value, 1.24%, is situated between 1.0 and 1.5% - which are the values

adopted by WHO (2004) in the estimative of total cost of accidents in countries with low and

medium developing, respectively. More important than the economic costs of road accidents,

are, however, the human and social costs: the physical and psychological suffering of

victims, and psychological suffering of relatives and people related to the victims, diseases of

psychological nature that attack victims and close relatives (depression, fear, etc.), lost of

quality of life of victims and their families, divorce of couples, separation of dear relatives due

hospital treatment and rehabilitation, etc.

1.2. TRAFFIC ACCIDENT COSTS

Namely, traffic accident costs can be divided in three main parts: economic cost; human and

social cost; and environmental cost. They will be summarized below.

Economic cost

In Brazil, two recent studies have been conduct by the Institute of statistics and economy

(IPEA) of the costs of road accidents: IPEA (2003) is a research about the accidents in the

city and IPEA (2006) is about accidents on highways. The average costs by type of accident

obtained in the studies are indicated on the Table 1. They were updated to December 2007




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by an inflation indicator well known in Brazil. Also on the Table 1 there is an indication of the

annual cost of accidents on the cities and on the highways, for Brazil.

Table 1– Costs of traffic accidents (values are in Brazilian reais updated to December 2007).

Description Highways Cities Country

Property damage only 18,075.00 4,125.00 -

Accidents with injury victim (R$) 92,341.00 22,077.00 -

Fatal accidents (R$) 449,018.00 182,262.00 -

All accidents (R$) 63,198.00 11,104.00 -

Total annual (billions R$/Year) 23.61 6.7 30.31

Human and social costs

More important than the economic cost of accidents is the human and social cost: physical

and psychological suffering of the victims, psychological suffering of the family members and

related ones, after crash psychological diseases strikes victims and related people with fear,

depression; quality of life loss for to all directly or indirectly involved, couples break-up, long

term hospital treatment and rehabilitation, etc.

Environmental cost

Accidents involving vehicles that transport dangerous products, in many cases, spills the

load of goods provoke big environmental damage into the soil, water, forests, animals, and

even on the climate. One thing is certain: these impacts are very hard to measure, however,

there is no doubt that these accidents cause huge harm to the environment and to the

society in general.

1.3. TARGETS TO REDUCE THE ACCIDENTS AND DEATHS ON TRAFFIC

Traffic can be considered as an open system constituted by human being, vehicles and

environment, which interact adequately with each other in most cases. When this interaction

does not occur in an appropriate manner, by fault of one or more associated factors related

to these three elements, an accident may happen.

A systemic view about the traffic accidents was represented in the well known Haddon matrix

form. Connected to the actions associated to each one of the three elements that composes

the transit system aiming to avoid accidents (pre-crash period), mitigate the consequences of

moment the accident happens (crash period) and mitigate the effects after it occurs (after-

crash period).

In fact, there are four macro-actions used with the objective to reduce accidents and death

on traffic:

Reduction of the risk exposure




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Reduction of the accident occurrence

Reduction of the accident severity

Improvement of the victim’s care

2. METHODOLOGY DESCRIPTION

The methodology used in this work was based on the bibliographic revision studied about

road safety measures and the evaluation studies on their effects. It was created a

methodology to choose primarily the locals where the roundabouts were built. The chosen

places have priority over other intersections because they used to have high rate of road

conflicts and also because there was some data available to analyze the before-after

situation at that specific locations. Jaú has the database with information from 2000 until

2007, as well as the dates of construction’s implementation, that were considered the limit

point to the before-after analysis.

Even though, it is necessary to choose a time frame that contains information for the analysis

of all places which have suffered infrastructures’ changes. The use of tools that help to

visualize the locations is essential to traffic safety works. This happens because all the

constructions related to traffic have to be analyzed including their surroundings and their

impact. Knowing this, interest’s points of Jaú were located on a digital map. Precisely, all the

roundabouts built after 1999 were added to a Geographic Information System – GIS for a

better visualization and spatial data analysis, numbering then from 1 to 15 by the criteria of

implementation data. After this point, it was initialized the accident database research on the

database of the Transport Secretary of Jaú and the Jaú Department of Transit. The State of

São Paulo Military police feed this database by the composition of documents known as

“Boletins de Ocorrências” (official reports about accidents) that are the form in which all

traffic agent or police describes the accident.

The topographic and the geometric project adopted in each roundabout was raise to better

understand their geometry before and after, and also how this could affect the local traffic.

This kind of analysis made possible to evaluate the roundabout’s performance in the

accident rate reduction in Jaú, making it feasible to compare to other locations.

After this geometric review, the cost-benefit analysis was calculated using a methodology of

Naïve Before-After studies described by Hauer (1997).

The most correct actions would be to consider other variables involved with the relation

between the absolute numbers of analyzed accidents; however, since there were not enough

data, it was used pure number along with a comparative mean of the period before and after

the construction of the roundabouts.

Based on this data, it was possible to simply analyze the accident variations related to the

growth or the shrink on the number of accidents at each roundabout by subtracting the




6

average of accidents before and after. This data associated to the costs of Brazilian

accidents (IPEA, 2003) and the cost of construction of the traffic calming device, allowed us

to come up with a benefit-cost analysis.

2.1. Naive Before – After Studies

The estimation of the effect of a treatment on safety always entails a prediction of what

safety would have been in the after period had the treatment not been implemented, and the

juxtaposition of this prediction to an estimate of what safety in the after period actually was.

Accordingly with Hauer(1997) in its simplest form, an observational Before-After study

consist of comparing the count of the “before” period accidents for an entity to its count of

“after” period accidents. The basic logic of a naive before-after study is that the count of

“before” period accidents is used to predict what would have been the expected count of

“after” period accidents had the treatment not been implemented. This way of predicting

reflects naive and usually unrealistic belief that the passage of time was not associated with

changes that affected the safety of the entity under scrutiny. In spite of its obvious flaw, the

Naive-Before study will be used here, because of the lack of data this is the only study that

can be made with the available data. The statistical analysis performed here was base on the

methodology presented in Hauer (1997) and is summarized below:

Let

π be what the expected number of target accidents of a specific entity in an

“after” period would have been had it not been treated; π is what has to be

predicted and

λ be the expected number of target accidents of the entity in the “after” period; λ

is what has to be estimated.

The effect of the treatment on safety is judged by comparing λ and π. In compare the two we

used:

δ=π – λ the reduction in the “after” period of the expected number of target accidents

(by kind or severity), or

θ=λ/π the ratio of what safety was with the treatment to what it would have been

without the treatment – the “index of effectiveness”.

When θ<1, the treatment is effective; when θ>1 it is harmful to safety.

So, the logical essence of an observational Before-After study is the comparison of a

prediction ( ) of would have been the expected number of target accidents of an entity in the

“after” period, had a treatment not been implemented, with an estimate of ( ) of what the

expected number of target accidents of the entity was with the treatment in place. General




7

expressions for doing so were given in Hauer (1997) and the entire process has been

structured into four basic steps, are shown in the next session.

Statistical Analysis of the naive Before-After Study

Some treatment has been implemented on entities numbered 1, 2,..., j,..., n. During the

“before” periods the accident counts were K(1), K(2),...K(n) and during the “after” periods the

accident counts were L(1), L(2),...,L(n). The duration of the “before” and “after” periods may

differ from entity to entity. Thus, the ratio of durations will be:

)( jrd

Duration of after period for entity j

Duration of before period for entity j

Because expected values are never known, but can be estimated from observed data, the

Greek letters with caret will be used meaning “estimate of” the parameter which it refers. In

Table 2 are the four steps summarized.

Table 2 – The summary of four steps computations

STEP 1 STEP 2

=Σ L(j) VÂR{ }= Σ L(j)

= Σ rd(j)K(j) VÂR{ }= Σ rd

2(j)K(j)

STEP 3 STEP 4

δ=π – λ VAR{ }= VAR{ }+ VAR{ }

θ*= (λ/π)/[1+VAR{ }/ π2] VAR{ }≈ θ

2[(VAR{ }/λ

2)+(VAR{ }/π

2)]/[1+VAR{ }/π

2] 2

3. CASE STUDY: JAÚ-BRAZIL

Jaú is a city of approximately 130.000 inhabitants located on the State of São Paulo, Brazil. It

is considered an average size town with big city problems, once its population is mainly

urban. Like Jaú, there are lots of towns in the country side. In Table 3 are listed a summary

of Jaú data.




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Table 3 – Summary data about accidents, population, fleet and index of accidents by fleet

Year

Number of Accidents

Fleet Population Total

number of accidents

Index of accident per fleet

Fatal Victims

Non fatal

victims

Proper Damage

Only

Iacc

total Iacc

fatal Iacc

victims Iacc

PDO 1997 10 713 1427 39.508 105.966 2150 54,42 2,53 18,05 36,12

1998 10 625 1263 39.193 107.968 1898 48,43 2,55 15,95 32,23

1999 7 701 1315 40.769 109.965 2023 49,62 1,72 17,19 32,25

2000 11 569 1257 43.177 112.104 1837 42,55 2,55 13,18 29,11

2001 9 470 1235 45.811 113.952 1714 37,41 1,96 10,26 26,96

2002 5 516 1225 48.596 115.889 1746 35,93 1,03 10,62 25,21

2003 10 622 1216 51.639 117.645 1848 35,79 1,94 12,05 23,55

2004 9 709 1331 54.733 121.333 2049 37,44 1,64 12,95 24,32

2005 11 744 1355 54.727 123.374 2110 38,56 2,01 13,59 24,76

2006 6 655 1379 58.698 125.399 2040 34,75 1,02 11,16 23,49

2007 6 743 1437 63.199 125.469 2186 34,59 0,95 11,76 22,74

(*) Iacc_total, Iacc_victims e Iacc_PDO given in accidents per 1,000 vehicles, Iacc_fatal

given in deaths per 10,000 vehicles.

3.1. Adopted actions by the Jaú municipality

According to Elvik and Vaa (2004), a common problem in accident and injury prevention

work is lack of motivation. Common reasons why many people do not want to get involved in

accident and injury prevention are that they do not regard accident as a problem or they do

not believe it is worth doing anything to prevent accidents.

These authors assume that local community safety programs have been found to reduce the

number of accidents in these communities significantly. However, not all local community

safety programs are successful. To succeed, a community needs good local accident

statistics, a capability to identify the most important local accidents problems and ways of

creating a strong motivation for improving safety. These programs usually have some

characteristics:

1. The systematic recording of accidents in a local community over a given period of

time;

2. On the basis of accident records, the dominant accident problems in the local

community are identified;

3. A steering group for accident prevention in the local community is set up, with

participation from all parties which are presumably able to contribute to preventing

accidents, including the municipality, schools, and the police;

4. The safety program is implemented. During the hole implementation period, changes

in the number of accidents and injuries are monitored closely and information on new

developments is given to all those participating in the program.

Worried about the traffic safety issue, Jaú municipality adopted a safety program since 2000,

and understanding the transit as an interdisciplinary issue and focused low cost road safety

effective solutions, invested basically on the macro-areas of education, engineering and




9

enforcement, adopted along with the transit and public transportation integrated

management technique.

3.2. The study of roundabouts usage to accident reduction

According to Elvik and Vaa (2004), in the chapter about roundabouts says that at road

junctions heavy traffic waiting times for traffic required to give away be long. This may tempt

road users to enter the junction with small margins. Frequent crossing and turning

maneuvers can create dangerous situations and make the traffic situation complex. Around

40% of all injury accidents reported to the police occurs at intersections.”

For them, converting intersections to roundabouts can improve safety and traffic flow.

Roundabouts can contribute to increasing road safety in the following ways; by theoretically

reducing the number of conflict points between the traffic streams passing through an

intersection from 32 to 20 at crossroads and 9 to 8 at T-junctions.

Road users entering a roundabout are require to give way to road users already in the

roundabout, no matter which road they are coming from, and thus are forced to observe

traffic at the roundabout more carefully all traffic comes from one direction. Road users

therefore do not have to observe traffic form several directions at the same time in order to

find a gap to enter the roundabout.

Roundabouts with offside priority eliminate left-turn in front of oncoming traffic roundabout

are built so that road users cannot drive a straight path through the junction but must drive

round a traffic island located in the middle of the junction. The roundabout with preference to

circling traffic presents, for the safety point of view, the following positive aspects: the

passage happens with low speed because the change of trajectory and need to stop or yield

to inside traffic; decision making to enter is done observing just one side, where the visibility

to driver is better; the number of conflict points at roundabouts is smaller, and in some cases,

eliminate the need for conversion to the left and crossing the opposite flow (maneuver

potentially dangerous).

According to Várhelyi (1996), experiences of rebuilding a large number of intersections on

arterial roads as roundabouts in England showed that the number of accidents decreased by

30-40%. As examples, he mention Simon in Switzerland, who also concluded that small

roundabouts increase safety, and Van Minnen, in the Netherlands, who reported that new

roundabouts reduced the total number of accidents by 50% and the number of casualties.

This way, 56 roundabouts were built from 2001 to 2007, as shown on the illustration below.




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Figure1: Roundabouts built in Jaú-SP BRAZIL

From these 56, it was randomly selected 15 to analyze the accidents before and after the

implementation, the locations of these 15 intersections are shown on the Figure 2.

Figure 2 – Map with the location of the 15 studied roundabout

On the next table there is a list of addresses for the roundabouts used in this project to

analyze the benefit-cost of the implementation of this kind of traffic calming infra-structure.




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Table 2 - Addresses for the roundabouts analyzed and dates of implementation

Roundabouts changed

J Date

Address

01 09/2001 Av. Isaltino do Amaral Carvalho x Av. João Ferraz Neto

02 04/2002 Rua Rui Barbosa x Av. Nenê Galvão

03 06/2002 Av. Caetano Perlatti x Av. Zezinho Magalhães

04 05/2003 Av. Décio Pacheco de Almeida Prado x Rua Dr. Amaral Carvalho x

Alameda Cel. Miranda Prado

05 06/2003 Rua Rui Barbosa x Rua Major Alfredo S. O. Romão x Rua D. Silveira

x Rua Tenente Navarro

06 08/2003 Av. Dr. Luciano P. de Almeida Prado Neto x Av. Antonio H. G. Pelegrina

x Av. Fernando de Lúcio x Rua Miro Campana

07 08/2003 Av. Dr. Luciano P. de Almeida Prado Neto x Rua Augusto Caseiro x

Rua José Blassioli

08 09/2003 Av. do Café x Av. Joaquim F. de Camargo x Av. Cmte João Ribeiro de Barros

09 05/2004 Rua Major Ascânio x Av. Brasil x Travessa Pereira Lima

10 07/2004 Av. Frederico Ozanan x Av. das Nações x Rua Jesuíno dos Santos

11 07/2004 Av. Frederico Ozanan x Av. Zezinho Magalhães x Rua Alfredo Leitão

12 02/2005 Rua Pereira de Toledo x Rua Pef. Mário Ferraz Magalhães x Av. Cmte João

Ribeiro de Barros

13 04/2005 Av. Frederico Ozanan x Rua Sampaio Bueno / Av. Frederico Ozanan x Francisco

Sampaio

14 04/2006 Av. do Café x Rua Irmã M. Gabriela x Av. Gustavo Chiozzi

15 12/2006 Av. Isaltino do Amaral Carvalho x Av. Dr. Quinzinho

The intersection number 13 was taken out of analysis because it was formed by two

intersections, and the data are aggregate for these two intersections so it was impossible

disaggregated the information about accident count for each one. In Figure 3 and 4 are

shown the drafts of before and after implementation of roundabouts in those 14 remain

intersections.




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01

02 03

04 05

06 07

08 09

10 11

AJUSTE

Av. Isaltino A. Carvalho

Av.

João F

err

az

Neto

9.30

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0

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R12.00

8.00

R11.8

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Av.

João F

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Av.

João F

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DEPOISANTES

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10

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Curv

a A

x= -3.6

622, y=

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310

Tangente

0,0

01

02

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0,0

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50,0

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a C

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0,0

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a D01

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R=

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Rua Rui B

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AV

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7.50

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4.50

9.0

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9.0

0

7.0

0

7.00

9.00

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6.0

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7.50

7.50

4.5

0

1.0

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4.5

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R12.46

R12.5

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Rua Rui Barbosa

Rua D

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Rua Tenente N

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Rua A

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POSTODE GASOLINA

Rua Rui Barbosa

Rua D

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Rua Tenente N

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Rua A

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DEPOISANTES

R6.0

0m

5.00m

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Av. Fernando de Lucio

DE ALMEIDA PRADO NETO

AVENIDA DR LUCIANO PACHECO

DEPOISANTES

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04 05 06 0708

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1718

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19

20

21

R= 4

5.0

0m

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

59°

R= 22.0

0m

35°

R=

22.6

0m

42

4344

R= 22.00m

15°

R= 1

0.00

m

45

46

47

10.66

8.0

0

R0.80

R0.80

R0.50

R0.8

0

R0.80

R1.00

8.0

0

8.0

0

7.0

0

7.00

6.00

9.00

9.00

8.0

0

9.0

0

9.0

0

9.00

5.65

8.21

Rua F

Av. A

AVENIDA DR LUCIANO PACHECO DE ALMEIDA PRADO NETO

RUA A

UG

USTO

CASEIR

O

RUA J

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LASSIO

LI

DEPOISANTES

8.0

0

8.0

0

9.00

9.0

0

9.00

9.0

0

7.007.00

7.00

7.00

8.0

08.0

0

R=

15.0

0m

19.15

10.8

5

7.9

4

6.8

7

5.8

7

4.9

5

4.1

0

3.3

3

2.6

4

2.0

2

1.4

8

1.0

3

0.6

6

0.3

6

0.1

5

1.691.731.771.811.841.881.901.931.951.961.981.992.002.00

26

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

4849

5051

27

01 02

0304

0506

07

08

09

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

12.29

12.1912.10

12.0011.90

11.80

11.7111.61

11.51

11.4911.57

11.74

12.02

12.41

12.82

13.20

13.57

13.77

13.77

13.5613.15

12.5211.64

10.488.97

6.761.24

52.2

4

52.6

3

6.97

6.95

7.08

7.13

7.18

7.27

7.48

7.83

8.33

8.97

9.76

10.74

11.47

11.95

12.23

12.30

12.17

11.87

11.43

10.84

10.09

9.16

8.05

6.71

5.12

3.20

0.86

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

2.00

0.63

9.00

50.8

5

11.2

0

21.55

8.8

1

R1.75

R1.00

R1.00

R1.00R

1.00

R1.00

R1.00

R1.

00

R0.5

0

R1.00R1.00

R2.00

3.00

6.50

4.0

0

4.0

0

6.6

0

6.60

3.504.5

0

4.50

4.50

5.5

0

6.50

4.00 3.75

8.00

6.30

6.5

0

8.0

0

Av.

Com

te. Jo

ão R

ibeiro d

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os

Av. d

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afé

Av. Joaquim Ferraz

Av.

Com

te. Jo

ão R

ibeiro d

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os

Av. d

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de CamargoAv. Joaquim Ferraz de Camargo

DEPOISANTES

POSTE

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POSTE

DEPOISANTES

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RUA MAJOR ASCÂNIO

R7.57

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6.00

6.00

6.0

0

6.0

0

7.50

0102

03

04

07

06

05

08

0,0

09

10

11

12

13

14

1516

17

18

1920

21

2223

24

25

2627

y

x

Praça Italo Baraldi

Av. F

rederico O

zanan

N01

R6.50 8.50

8.50

8.50

8.50

8.0

0

8.50

8.5

0

ANTES DEPOIS

1

2

34

678

9

10

11

13

14

15

1621

2019

18

17

12

(0,0)

x

y

Praça Italo Baraldi

Av. das Nações

Av. F

rederic

o O

zanan

R. Jesuíno dos Santos Av. das Nações

R. Jesuíno dos Santos

posto pit stop

Av. Zezinho Magalhães

Rua Alfredo Leitão

poste

R13.50 posto pit stop

Av. Zezinho Magalhães

Rua Alfredo Leitão

poste

4.85

12.9

3

8.5

0

8.50

8.5

0

R5.00

R5.00

13.8

8

1.13

1.98

0.49

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63.0

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8.00

8.1

5

8.0

0

Av. F

rederic

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zanan

Av. F

rederic

o O

zanan

DEPOISANTES

Figure 3 – Drafts of before and after implementation of roundabout at the intersections 1 to 11.




13

12

13

15

RU

A P

RE

F. M

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DEPOISANTES

RU

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RUA ANTONIO SANTANA GALVÃO

1.50

R11.10

R3.50

16.19

24

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6

0.82

1.65

2.43

3.09

2.92

1.76

0.42

0.67

1.42

1.41

0.62

3.00

6.04

7.0

0

4.00

4.60

4.72

4.50

7.60

7.60

7.6

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4.62

4.5

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DEPOISANTES

Av. d

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Av. G

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R. Irm

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POSTE CPFL

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00

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9

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abriela

Av. d

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Av. Iz

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Av. Dr. Quinzinho

R8.0

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8.00 8.00

8.0

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1

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7.00

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0

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0

4.4

0

4.4

0

6.5

0

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1

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DEPOIS

postes propaganda

registro saemja

registro saemja

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Tampão

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8.0

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0

4.4

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4.4

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ANTES

Figure 4 – Drafts of before and after implementation of roundabout at the intersections 12, 14 and 15.

3.3. Data and computations

The data and computation for those 14 intersections are shown in Table 2 for accidents with

property damage only. In Table 3 are the end results of computation for those 14

intersections for accidents property damage only. In Table 4 are the data and computation

for those 14 intersections for accidents with victims and in Table 5 are the respective end

results. The computations follows the methodology describe in Hauer (1997).

Tabela 2 – Data and computations for accidents with property damage only

intersection number

Years Before

Years After

Acc. Before

Acc. After

J K(j) L(j) rd(j) rd(j).K(j) rd2(j).K(j)

1 2 8 33 65 4.00 132.00 528.00

2 3 5 12 9 1.67 20.00 33.33

3 3 5 19 8 1.67 31.67 52.78

4 4 4 4 0 1.00 4.00 4.00

5 4 4 27 18 1.00 27.00 27.00

6 4 4 1 4 1.00 1.00 1.00

7 4 4 3 1 1.00 3.00 3.00

8 4 4 8 13 1.00 8.00 8.00

9 5 3 3 2 0.60 1.80 1.08

10 5 3 10 9 0.60 6.00 3.60

11 5 3 19 5 0.60 11.40 6.84

12 6 2 4 0 0.33 1.33 0.44

14 7 1 13 1 0.14 1.86 0.27

15 6 2 46 11 0.33 15.33 5.11

Sums 146 264.39 674.45




14

Table 3 - Results for accidents with property damage only

λ= 146.00 σ{λ}= 12.08

π= 264.39 σ{π}= 25.97

δ= 118.39 σ{δ}= 28.64

θ= 0.55 σ{θ}= 0.07

Tabela 4 – Data and computations for accidents count with victims

intersection number

Years Before

Years After

Acc. Before

Acc. After

J K(j) L(j) rd(j) rd(j).K(j) rd2(j).K(j)

1 2 8 15 26 4.00 60.00 240.00

2 3 5 5 6 1.67 8.33 13.89

3 3 5 5 1 1.67 8.33 13.89

4 4 4 2 0 1.00 2.00 2.00

5 4 4 4 5 1.00 4.00 4.00

6 4 4 0 3 1.00 0.00 0.00

7 4 4 3 1 1.00 3.00 3.00

8 4 4 2 5 1.00 2.00 2.00

9 5 3 3 2 0.60 1.80 1.08

10 5 3 5 4 0.60 3.00 1.80

11 5 3 10 2 0.60 6.00 3.60

12 6 2 4 0 0.33 1.33 0.44

14 7 1 2 0 0.14 0.29 0.04

15 6 2 19 6 0.33 6.33 2.11

Sums 79 61 106.42 287.85

Table 5 - Results for accidents with property damage only

λ= 61.00 σ{λ}= 7.81

π= 106.42 σ{π}= 16.97

δ= 45.42 σ{δ}= 18.68

θ= 0.56 σ{θ}= 0.11

4. INTERPRETING THE RESULTS

The intersections analysed had a reduction of 118.39 ± 28.64 in the total number of

accidents or 45% ± 7% of reduction in the total number of accidents. Also had a reduction of

45.42 ± 18.68 in the number of accidents with victims or 44% ± 11% of reduction in the

number of accidents with victims.

Thus, the noted reduction in safety reflects not only the effect of implementation of

roundabout in these 14 intersections but also the effects of factors such as traffic, weather,

vehicle fleet, driver behaviour, inclinations to report accidents and so on. It is not known what

part of the change can be attributed to the implementation of roundabouts and what part is




15

due to the various other influences. And also the noted change in safety may be in part due

to the spontaneous regression-to-the mean and not due to implementation of roundabout.

Inasmuch as it is the only method at hand, it will be used to computation the cost benefit

analysis, but we need to have in mind the disclaimers state above.

5. BENEFIT-COST ANALYSIS

The benefit-cost analysis was based on available and possible data, such as building costs,

average of accidents before and after its implementation, and the cost of accidents for the

Brazilian case develop by IPEA (2003). In this case, neither the population nor the fleet was

used to analyze the Benefit cost value.

It was use the total cost of built the roundabouts as the cost. The benefit cost was calculated by the estimative of reduction of accidents in the naive approach for the intersections and periods in analysis, using the results obtained in section 3. Table 6-Accident costs of IPEA/2003 update to June of 2008 for cities.

Type of accident Cost (R$/accident)

Property Damage Only 4,275.00

With non fatal victims 22,882.00

With fatal victims 188,902.00

All types of accidents 11,509.00

The costs of building these 14 roundabouts actualized to June of 2008 were R$ 348,000.001.

The total number of accidents reduction in the best scenery is 118.89 + 28.64 = 148.53

accidents without victims and 45.42 + 18.68 = 64.20 accidents with victims, which makes

monetary beneficial of R$ 2,095,230.74 for the best estimates. For worst scenery we have an

reduction of 118.89 -28.64 = 90.25 accidents without victims and 45.42 -18.68= 26.74

accidents with victims, which makes a monetary beneficial of R$ 995,565.12 for the worst

scenery. For the median scenery we have a monetary beneficial of R$ 1,545,397.93. Those

numbers are summarized on Table 7.

Table 7- Benefit –cost ratios estimatives in different sceneries

Scenery Benefit

R$

Cost

R$ B/C

Best 2,095,230.74 348,000.00 6.02

Worst 995,565.00 348,000.00 2.86

Median 1,545,397.00 348,000.00 4.44

1 Brazilian Reais




16

6. FINAL CONSIDERATIONS

Although the benefit-cost ratio are high for any of those sceneries we must have in mind that

was used the naive Before-After studies and the changes encounter here are not only due

the implementation of roundabouts. However, Brazil has an increasing in the motorization

rate in the last years, in special in motorcycle fleet. Some studies point an increasing in the

number of accidents, in great extent with fatal and injured victims with this kind of

transportation mode (MS, 2007). Jaú also had an increasing in the percentage of

motorcycles in the fleet, and almost the half of deaths was motorcyclists in 2008. As in this

study the changes in vehicles flows are not take into account, the figures could be even

better. Another consideration that must be made is the fact that the intersections chosen to

be change in roundabouts had high number of conflicts, and the results could have been

high due this fact, in other words, could have brought some bias to the sample, and an

improved methodology must be applied in future work, using for example, a comparison

group.

But these roughly analysis shows even in the case of Brazil were the cost of accidents are

relatively low in comparison with developed countries, the roundabouts could have a benefit-

cost ratio.

We would like to highlight also that the cost of constructions of the roundabouts were low

because the design and construction was made with the employees of the Secretary of the

Transport at that time. It shows also that roundabouts can be a low cost traffic engineering

measure to reduce accidents in developing countries, were the work force is cheap in

comparison with developed countries, with advantage of low cost of maintenance if compare

with traffic lights. Inasmuch as Brazil has high rates of drivers running red traffic lights,

roundabout have one more advantage: as is well-known the roundabout is self regulated and

helps to reduce speeds and reduce the severity of accidents.

Therefore the percentage of reduction in the number of accidents found in this study is in

accordance which is founded in the literature, around 50% of reduction in accidents and

severity (Várhely, 1996). In contradiction, other studies founded that the introduction of

roundabouts reduces the severity of accidents, but increase the number of property damage

accidents until 73% (Elvik and Vaa, 2004). In this study of case was found that the number of

property damage accidents and severity of accidents were reduced with roundabouts.

REFERENCES

Elvik,R and Vaa T.(2004) THE HANDBOOK OF ROAD SAFETY MEASURES. Elsevier.

Hauer, E. (1997). Observational Befpre-After Studies In Road Safety – Estimating the effect

on highway and traffic engineering measures on road safety. Pergamon.

Ipea (2003). Relatório Ipea/2003 Available at www.ipea.gov.br. Access in July 2008.

Ipea (2006). Relatório Ipea/2006 Available at www.ipea.gov.br. Access in July 2008.




17

MS (2007). Perfil de Mortalidade do Brasileiro Ministério da Saúde. Available at

http://portal.saude.gov.br/portal/arquivos/pdf/coletiva_saude_061008.pdf. Access in

December, 2009.

Várhleyi, A. (1996). Dynamic speed adaptation based on information technology – a

theoretical background. Bulletin 142, Lund University.

WHO (2004). World report on road traffic injury prevention, World Health Organization.

Geneva.

http://portal.saude.gov.br/portal/arquivos/pdf/coletiva_saude_061008.pdf

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