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Costa Rica experience in the application of the IRI parameter as
criteria for the acceptance of road
maintenance and rehabilitation projectsBy
Ing. Luis Diego Herra G.
University of Costa Rica, LanammeUCR.
Technical Audit Unit
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About LanammeUCR
Law number 8814
National Laboratory of Materials and Structural Models
Technical audits of projects in execution.
Training and accreditation programs for laboratorytechnicians
and field inspectors.
Research programs on the problems of paved roadinfrastructure in
the country.
Evaluation of the entire paved national network.
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Allows to connect the farthest regionsof the country with the
main cities, theCosta Rican road network is one of thedensest in
America (0.7 km / km2).
National Paved Road Network in CRC
Having a dense Road Network implies achallenge for decision
makers in thetransport sector in Costa Rica.
More kilometers to attend
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Manteinance scheme in Costa Rica
It is based on the payment for activities through unit prices.
Whereprivate companies compete to opt for the maintenance of one of
the22 conservation areas that divide the country.
Private companies(Costa Rica´s Road
Authority)
Since this contracting system isbased on unit prices, it
becamenecessary to implement qualitycontrol systems such as
IRI.
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Background
Since2016
Started the implementation ofthe International RoughnessIndex
(IRI) parameter as acriterion for the acceptanceof road maintenance
andrehabilitation projects, suchas asphalts overlays
andrehabilitations with cementtreated bases.
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IRI specification: Two cases
Classification Maximum IRI value for a base section of 100 m
Primary Road Network 1.9 m/km
Rest of the roads 2.5 m/km
Initial Range of IRI Final IRI (m/km)
Less or equal to 2.5 At least keep initial IRI
2.5 < Initial IRI < 3.6 Reduction of 10%
3.6 ≤ Initial IRI ≤ 6.4 Less than or equal to a 3.2
Initial IRI > 6.4 50% reduction and less than or equal to
5.0
Rehabilitation projects
Overlays
Rehabilitation Overlay
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Contents of the investigation
This research collects and analyzes information about the
roughness of allthe asphalt overlays and cement treated bases that
were developed from2016 to 2018.
726 km of asphalt overlays
296 km of rehabilitations
Comparison between the
roughness in projects
executed before and after
the specification
(rehabilitations and
overlays). Effect of the
specification
Specification compliance
percentages. To
determine if the
specification is
achievable
Comparison between the
surface roughness
calculations made by
LanammeUCR against a
sample of roughness
calculations made by every
quality control laboratory
hired by the Administration.
To determine if they are
not benefiting the
contractor
Analysis of the influence
of the slope and curves
in the IRI values. Its
more difficult to build
and overlay in a
mountain route.
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2.7
2.0
41%
91%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Anterior a la licitación pública 2014LN-000018-0CV00 (1306 datos
analizados)
Posterior a la licitación pública 2014LN-000018-0CV01 (1282
datos analizados)
Po
rcen
taje
de c
um
plim
ien
to
Pro
me
dio
de
IR
I
Promedio de MRI Porcentaje de cumplimientoCompliance
percentageAverage IRI
IRI Before and After the specificationCase 1: Rehabilitation
Co
mp
lian
ce p
erc
en
tage
Ave
rage
IRI
Before the specification After the specification
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93% 93%87%
63%70%
54%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
1 2 3
Po
rce
nta
je d
e c
um
pli
mie
nto
Criterio de la especificación
Posteriores a la licitación pública 2014LN-000018-0CV00 (sin
eliminar singularidades)
Anteriores a la licitación pública 2014LN-000018-0CV00 (sin
eliminar singularidades)
IRI Before and After the specificationCase 2: Overlays
After the specification
Before the specification
Co
mp
lian
ce p
erc
en
tage
Reduction of 10% Less than or equal to 3.2 50% reduction and
less than or
equal to 5.0
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We found that the compliancepercentages were fine, up to 90
%,except in one case.
In overlays, when we had sections ofthe road with good initial
IRI values,less tan 2,5 m/km.
Why? Because after placing theoverlay, they need to accomplish
anIRI value equal or better than theinitial IRI.
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Specification compliance percentagesin overlays: Case 1 At least
keep initial IRI
Initial IRI (evaluated data)
Compliance percentage Average improvement percentage
Co
mp
lian
ce p
erc
en
tage
(%
) |
Ave
rage
im
pro
vem
en
t p
erc
en
tage
(%
)
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Overview of IRI in overlay projects
Co
mp
lian
ce p
erc
en
tage
(%
) |
Imp
rove
me
nt
pe
rce
nta
ge (
%)
Fin
al IR
I (m
/km
)
Initial IRI (m/km)
Average Final IRI Improvement percentage Compliance
percentage
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Comparison: LanammeUCR / QC labs
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8
Cu
mu
lati
ve
fre
qu
en
cy
Difference between the measurements made by the LanammeUCR and
those made by the QC labs
LGC OJM ITP CACISA VIETOLab 1. Lab 2. Lab 3. Lab 4. Lab 5.
As you can see most of the data has positive differences, it
means that QC labs reported lower IRI values.
Around 0,1 m/km lower if you analyze the 50th percentile of the
curves, except the green curve that represents Lab 2, which
presents a difference zero in the 50th percentile
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98%
90%
80%78%
100%
93%
95%
88%
72%
76%
100%
89%
60%
65%
70%
75%
80%
85%
90%
95%
100%
LGC OJM ITP CACISA VIETO Promedio ponderado
Po
rcen
taje
s d
e c
um
plim
ien
to
Laboratorio de verificación LanammeUCR
Comparison: LanammeUCR / QC labs
Lab 1.QC labs
Lab 2. Lab 3. Lab 4. Lab 5. Average
LanammeUCR
Co
mp
lian
ce p
erc
en
tage
s
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Influence of the slope and curves in the IRI values
Description of the
segment
Curvature ratio
R (m)
No curves More than 390
Smooth curves 130 - 390
Sharp curves 60 - 130
Very sharp curves Less than 60
(Jiménez, 2019)
Around 10 000 IRI values were analyzed.
Curve categorization Slope categorization
Type of terrain Slope (%)
Flat P ≤ 5
Wavy 5 < P ≤ 15
Mountainous 15 < P ≤ 30
Steep P > 30
Steep
Average IRI values:
Mountainous
Wavy
Categories
Flat
No curvesSmooth curves
Sharp curvesVery sharp
curves
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Conclusions
• After the IRI specification it was observed and improvement
inthe surface roughness of maintenance projects. 50 %
inrehabilitations and 29 % in overlays.
• A difference between 0 and 0.1 was observed between the
IRImeasurements made between LanammeUCR and the rest ofthe
laboratories
(Jiménez, 2019)
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Conclusions
• There is a relation between the road geometry and
theroughness, slope and curves could affect the constructiveprocess
and consequently affect the IRI of the road.
• The roughness affectation during construction is bigger
whenthere is a combination of slopes and curves.
(Jiménez, 2019)
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Thank [email protected]
