*Co esponding au ho . E-mail: da id. ehak@ sb.cz
Copy igh © 2020 The Au ho (s). Published by VGTU P ess
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TRANSPORT
ISSN 1648-4142 / eISSN 1648-3480
2020 Volume 35 Issue 3: 300–314
h ps://doi.o g/10.3846/ anspo .2020.12414
IDENTIFYING CRITICAL ELEMENTS OF ROAD INFRASTRUCTURE
USING CASCADING IMPACT ASSESSMENT
Da id REHAK1*, Da id PATRMAN2, Ve onika BRABCOVÁ3, Zdeněk DVOŘÁK4
1, 2, 3Facul y o Sa e y Enginee ing, Technical Uni e si y o Os a a, Czech Republic
4Facul y o Secu i y Enginee ing, Uni e si y o Žilina, Slo ak Republic
Recei ed 3 Oc obe 2019; e ised 16 No embe 2019; accep ed 9 Janua y 2020;
i s published online 4 May 2020
Abs ac . Road anspo is a key means o anspo ing people and ca go on land. I s pa icula ad an ages a e speed and
ope abili y, which a e balanced, howe e , by dependence on oad in as uc u e. Road in as uc u e eliabili y is anim-
po an ac o in i s unc ioning. I some elemen s o oad in as uc u e a e dis up ed o ail, he unc ion o dependen
in as uc u es, such as he in eg a ed escue sys em o indus y, a e also impai ed and may ail. These impo an elemen s
o oad in as uc u e should be iden i ied as c i ical and be gi en g ea e a en ion when iden i ying weaknesses and im-
plemen ing subsequen secu i y measu es. This a icle in oduces he Iden i ying C i ical Elemen s o Road In as uc u e
(ICERI) me hod, which was designed o make use o Cascading Impac Assessmen s (CIA). The use o CIA allows c i ical
elemen s o be iden i ied h ough impac escala ion analysis. These impac s can he e o e be moni o ed no only in oad
anspo in as uc u e bu also ac oss he en i e c i ical in as uc u e sys em.
Keywo ds: c i ical in as uc u e, oad in as uc u e, c i ical elemen s, cascade e ec s, iden i ica ion, ICERI me hod.
In oduc ion
The impo ance o anspo in he mode n wo ld is e-
lec ed by i s inclusion in 2008 in o he Eu opean c i ical
in as uc u e sec o s (EC 2008), unde which he Eu o-
pean Council speci ied ou sub-sec o s: oad anspo ,
ail anspo , ai anspo and wa e way anspo (in-
cludes inland wa e ways anspo and ocean and sho -
sea shipping and po s). Road anspo cu en ly has an
i eplaceable ole in he Eu opean anspo a ion ne wo k.
This ac is suppo ed by a signi ican ly g ea e a e o mo-
o iza ion and in he g ow h o mo o way ne wo k densi y
in 2006–2016, which ook place in i ually all Eu opean
coun ies (UNECE 2018). Ano he s a is ic showing he
inc easingly impo an ole o oad anspo is he ongo-
ing g ow h o cabo age oad anspo ac oss Eu ope in
2013–2017 (Eu os a 2018).
The ounda ion o a unc ioning anspo sys em
is high-quali y and highly eliable in as uc u e. This
anspo in as uc u e comp ises elemen s (EC 2006) so
signi ican ha hei ailu e would cause a ic collapse
(Jenelius 2007). These elemen s a e e e ed o as c i ical,
and hei impo ance in he anspo in as uc u e sys-
em can be de i ed om hei le el o impac on depend-
en elemen s (Rinaldi e al. 2001). Indeed, in he con ex
o his a icle, c i icali y is unde s ood as he ela i e im-
po ance and signi icance o a gi en elemen ha also ex-
p esses he ulne abili y o ha elemen and he po en ial
ad e se e ec s o i s ailu e wi h ega d o he links in ha
sys em. Assessmen o he c i icali y o elemen s in e ms
o sa e y (e.g., Amb os e al. 2019) is no he subjec o
his a icle.
C i ical elemen s equi e g ea e a en ion, which
means hey mus be iden i ied ea ly and ha e hei e-
silience le els analysed (e.g., Rehak e al. 2019a; Nan,
Sansa ini 2017; Be occhi e al. 2016). In he con ex o
assessing cu en isks (e.g., Giannopoulos e al. 2012),
adequa e secu i y measu es can subsequen ly be adop ed
o enhance hei p o ec ion (e.g., Š olle e al. 2018; Klein,
Hu e 2017; Labaka e al. 2015; H omada, Lukas 2012).
Cu en s udies and publica ions dealing wi h iden i-
ying c i ical elemen s in oad anspo can be ca ego-
ized in o wo g oups. The i s g oup ep esen s uni e sal
me hods applicable o all a eas o anspo , namely oad,
ail, ai , ship (e.g., D ořák e al. 2017). The second g oup
comp ises speci ic me hods ha ocus exclusi ely on oad
T anspo , 2020, 35(3): 300–314 301
anspo . This g oup mos o en iden i ies c i ical links
o nodes in he oad ne wo k. To iden i y hese c i ical
elemen s, a ull ne wo k scan me hod is mos o en ecom-
mended (e.g., Jenelius e al. 2006; Taylo e al. 2006). This
me hod is based on a sys ema ic analysis o he impac on
accessibili y o ne wo k sec ions in he e en o hei clo-
su e. Howe e , in cases o e y la ge oad ne wo ks, his
in ol es a complica ed and leng hy ma hema ical calcula-
ion (e.g., la ge ci ies o agglome a ions). Fo his eason,
a ull ne wo k scan app oach may in some cases appea
imp ac ical (Chen e al. 2012).
Because o hese compu a ional demands, an al e na-
i e me hod was de eloped. This me hod uses a pa ial
ne wo k scan algo i hm based on analysing he leng h and
numbe o eplacemen ou es o gi en sec ions (Yang
e al. 2016). Ano he iew o e s a me hod based on he
link edundancy o a sub-ne wo k, namely he a ailabili y
o eplacemen ou es (Yu e al. 2014). This me hod uses
wo indexes o assess c i icali y: he link edundancy index
and link c i icali y index. The au ho s men ion ha his
me hod is much mo e e ec i e in iden i ying he same
c i ical elemen s han he ull ne wo k scan me hod men-
ioned abo e.
Ano he me hod is o iden i y c i ical elemen s based
on he mac oscopic undamen al diag am heo y (Dong
e al. 2017). The au ho s desc ibe his app oach as he e-
la ionship be ween a ic olume and he densi y o a oad
ne wo k and he ela ionship be ween a ea-weigh ed ol-
ume and he o al a ic amoun in a ne wo k. Ye ano he
me hod is based on he Ne wo k Robus ness Index (Sco
e al. 2006), which makes i possible o de e mine he al-
ue o indi idual segmen s o links in he en i e mo o way
sys em while iden i ying c i ical links equi ing imp o e-
men . Ano he possible me hod is assessing he c i ical-
i y o elemen s h ough hei ulne abili y (Oli ei a e al.
2014; Taylo , D’Es e 2007) o signi icance (Rupi e al. 2015).
This e iew e ealed ha no speci ic me hod o iden-
i ying he c i ical elemen s o all linea , poin and a eal
opological s uc u es is cu en ly a ailable (Sli ko a e al.
2018). One o he main, ob ious easons is he inabili y
o e alua e he co ela ion be ween elemen s wi h di e -
en opologies. I is also e iden ha none o he speci ic
me hods allows a sys emic assessmen o he in ensi y o
sp eading impac . When he c i icali y o elemen s and
hei signi icance and links o dependen elemen s a e
e alua ed in he scope o e alua ing he e i o ial uni , an
analysis o sp eading impac could help d aw a en ion o
hei signi icance and links o hese dependen elemen s.
A po en ial solu ion can be ound in implemen ing he
esul s o cascade impac assessmen (Rehak e al. 2018).
Based on he abo e, he a icle in oduces he Iden i ying
C i ical Elemen s o Road In as uc u e (ICERI) me hod,
which is sui able o ICERI using Cascading Impac As-
sessmen (CIA). The use o CIA allows c i ical elemen s o
be iden i ied using an impac sp ead analysis. These im-
pac s can be moni o ed no only in he sub-sec o o oad
anspo bu also ac oss he en i e c i ical in as uc u e
sys em.
1. In as uc u e elemen s o oad anspo
Road in as uc u e consis s mainly o oads o di e en
class (mo o ways, exp essways, oads, local oads). Ac-
co ding o he Commission Regula ion (EC 2006), o he
elemen s o oad in as uc u e a e land, oad bodies ( u -
ows, embankmen s, d ainage equipmen ), ci il enginee -
ing (b idges, unde passes, o e passes, unnels, a alanche
and alling ock p o ec i e s uc u es, snow ba ie s), le el
c ossings, a ic signs and signalling, elecommunica ions
equipmen and ligh ing equipmen (Lei ne e al. 2019).
Depending on hei impo ance, some elemen s a e
indica ed as c i ical in as uc u e elemen s and can be
classi ied a Eu opean o na ional le els. How Eu opean
c i ical in as uc u e elemen s a e designa ed is de ined
by he Council Di ec i e (EC 2008). Elemen s ha can be
ca ego ized as such all in o wo sub-sec o s: ene gy and
anspo . Designa ing na ional elemen s o c i ical in a-
s uc u e, howe e , is dependen on he indi idual coun-
y. The es ablished c i e ia ha elemen s mus mee o be
designa ed as elemen s o na ional c i ical in as uc u e
o en a y widely be ween coun ies, esul ing in ambigu-
ous classi ica ion (Sli ko á e  al. 2015). Some membe
s a es also o en illogically assign he abo e-men ioned
c i e ia. The le el o signi icance o an elemen in a c i i-
cal in as uc u e sys em may also no be app op ia ely
conside ed when i is de ined. In p ac ice, si ua ions hen
a ise unde speci ic c i e ia whe e no elemen o only ew
elemen s can be iden i ied as elemen s o c i ical in a-
s uc u e.
1.1. Links be ween elemen s o oad in as uc u e
When assessing he impo ance o indi idual elemen s,
hei signi icance and co ela ion in he c i ical in a-
s uc u e sys em mus be conside ed. The co ela ion o
elemen s, meanwhile, is de e mined by he links be ween
hem. The wo k o au ho s Rinaldi e al. (2001) is pi o al
in e alua ing he links be ween elemen s. This esea ch
demons a ed he in e dependence o c i ical in as uc-
u e elemen s and de ined ou ypes o link:
– physical ( he ype o in e dependency when each o
wo in as uc u es a e dependen on he ma e ial
ou pu (s) o he o he );
– cybe ( he ype o in e dependency when an in a-
s uc u e is dependen on he in o ma ion ansmi -
ed h ough he in o ma ion in as uc u e);
– geog aphic ( he ype o in e dependency when local
en i onmen al e en s can c ea e s a e changes in all
in as uc u es);
– logical ( he ype o in e dependency when he s a e
o each o wo in as uc u es depends on he s a e o
he o he h ough a mechanism ha is no a physical,
cybe o geog aphic connec ion).
These ypes o links can be u he classi ied acco ding
o hei s a e, which can ha e h ee o ms: dependence,
in e dependence and in luence (Rehak, No o ny 2016).
Dependence is de ined as a link o connec ion be ween
wo in as uc u es h ough which he s a e o one in a-
302 D. Rehak e al. Iden i ying c i ical elemen s o oad in as uc u e using cascading impac assessmen
s uc u e is a ec ed by o co ela es wi h he s a e o he
o he . In e dependence e e s o a wo-way ela ionship
be ween wo in as uc u es ha a ec s o co ela es wi h
he s a e o each in as uc u e. Gene ally speaking, wo
in as uc u es a e in e dependen i each is dependen
on heo he . By con as , in luence is cha ac e is ic ha
has no need o iden i y a ela ionship o i . An example
may be a si ua ion in which he assessed elemen B is no
dependen on he unc ion o elemen A, bu may be posi-
i ely o nega i ely in luenced by elemen A.
Ano he possible me hod o classi ying links is ep e-
sen ed by hei di ision acco ding o he le el o he link,
speci ically (Rehak e al. 2016):
– sys emic le el– his is he ype o link ep esen ed
by he dependence o in luence o sec o s ac oss he
en i e c i ical in as uc u e sys em (e.g., he depend-
ency o he in eg a ed escue sys em on oad in a-
s uc u e);
– sec o al le el– his is he ype o link ep esen ed by
he dependence o in luence o sub-sec o s wi hin a
gi en c i ical in as uc u e sec o (e.g., he impac
o dis up ed oad in as uc u e on ail anspo );
– sub-sec o al le el– his is he ype o link ep esen ed
by he dependence o in luence o indi idual ele-
men s wi hin a gi en sub-sec o (e.g., he dependence
o a mo o way on a mo o way b idge o he e ec o
mo o way ailu e on su ounding oads).
1.2. Classi ica ion o in as uc u e elemen s
acco ding o hei opological s uc u e
An impo an ac o in iden i ying c i ical elemen s o
oad anspo is hei opological s uc u e. F om he pe -
spec i e o opology, hese elemen s can be classi ied simi-
la ly o ailway in as uc u e in o h ee basic g oups: (1)
linea , (2) poin , (3) a eal elemen s (Sli ko a e al. 2018).
The i s g oup ep esen s linea o line elemen s,
which in he case o oad in as uc u e a e he linea
elemen s o mo o ways and oads o di e en ca ego ies.
Thei impo ance depends on he pe o mance hey p o-
ide, such as he capaci y and in ensi y o a ic in a gi en
a ea (Pa man e al. 2019) and he le els o he links o
dependen o in luenced elemen s.
The second g oup is poin elemen s, which in he case
o oad in as uc u e a e ep esen ed by, o example,
b idges, unnels o junc ions. The pe o mance o hese el-
emen s is usually de ined by a ic pe meabili y (Pa man
e al. 2019), whe eas dependen o in luenced elemen s
a e oad sec ions (i.e., linea elemen s) connec ed o hese
poin elemen s.
The hi d g oup comp ises a eal elemen s. In he case
o oad in as uc u e, hese a e, o example, bus s a-
ions. The pe o mance o hese elemen s is de ined by he
numbe o ehicles passing pe uni o ime. Iden i ying
dependen o in luenced elemen s in his g oup in oad
in as uc u e is al eady no longe possible. The impac s
a e al eady a ec ing commu e s.
2. Sp ead and assessmen o cascading impac s
in a c i ical in as uc u e sys em
The co e o impac s ha sp ead h ough a c i ical in a-
s uc u e sys em is he ailu es occu ing om he ad e se
e ec s o sa e y isks (i.e., he causes o dis up ion o o
ailu e o c i ical in as uc u e elemen s). These isks can
be o an ex e nal o in e nal na u e. The impac s can hen
di ec ly a ec socie y (di ec impac s), sp ead ac oss c i i-
cal in as uc u e and c ea e addi ional dis up ions ha
ha e addi ional impac s (cascading impac s). As a esul ,
he cascading impac s can a ec a single elemen simul a-
neously (syne gis ic e ec s) (Rehak e al. 2018). A g aphic
ep esen a ion o how hese impac s sp ead in a c i ical
in as uc u e sys em is shown in Figu e 1.
Cascading e ec s a e he e ec s caused by dis up ion
o o he ailu e o c i ical in as uc u e elemen s. These
hen u he sp ead ac oss he c i ical in as uc u e and
cause dependen elemen s o ail, which esul s in o he
impac s escala ing (Rehak e al. 2018). An example migh
be he e ec o a sa e y isk R2 (e.g., e o is a ack) in
sec o S2 (e.g., he elec ic powe indus y). As a esul
o his ad e se e ec , he unc ionali y o S2 sec o is dis-
up ed, which hen cascades in o he dependen S3 sec o
(e.g., anspo sec o ). Dis up ing bo h sec o s esul s in a
cascading impac on socie y as a whole. This speci ic si u-
a ion ep esen s he sp ead o cascading e ec s o com-
mon-cause ailu es, i.e. when wo o mo e in as uc u e
ne wo ks a e dis up ed simul aneously (Ko zanikolaou
e al. 2013).
Figu e 1. Rep esen a ion o how e ec s sp ead in a c i ical
in as uc u e sys em (Rehak e al. 2018)
S1S2
S a e secu i y Economy Basic human needs
Syne gy
In e nal and ex e nal secu i y isks
S1S1
S2
RRR
C i ical in as uc u e sys em
Socie y
S
Rsecu i y isks
c i ical in as uc u e sec o s
cause o dis up ion o o ailu e o he c i ical in as uc u e
di ec impac
cascading impac
syne gis ic impac
T anspo , 2020, 35(3): 300–314 303
CIA is an impo an ool in examining c i ical in a-
s uc u e. Wi hou p edic i e modelling ools, he po en-
ial impac s o dis up ion o o ailu e o c i ical in a-
s uc u e elemen s canno be iden i ied p omp ly. The
s a ing poin o cascade impac assessmen is a de ailed
analysis o he sys em in which links be ween elemen s a e
assumed (Zimme man, Res epo 2009). Analysing hese
links and de e mining hei in ensi y is hen necessa y.
Me hods ha assess cascading impac s in a c i ical
in as uc u e sys em p ima ily ocus on he elec ici y
sec o , which was designa ed in he P esiden ial Policy
Di ec i e PPD-21 as a uniquely c i ical sec o (The Whi e
House 2013). Howe e , om he pe spec i e o e alua ion,
hese me hods a e applicable e en o o he echnically o i-
en ed c i ical in as uc u e sec o s.
The i s majo s udy o he assessmen o cascade e -
ec s in he con ex o powe ailu e was conduc ed by
Bie and Wang (2002). Acco ding o he au ho s, cascad-
ing ailu es in he powe gene a ion indus y a e usually
caused by common mode ailu es such as connec ion ail-
u e, cabine ailu e, e c. In hei wo k, hey published a
i e-pa algo i hm comp ising ailu e analysis, ne wo k
opology, ne wo k connec i i y assessmen , sys em s a us
e alua ion and index s a is ics.
Ano he a ea o impo ance is examining he p obabil-
i y o a cascading ailu e de eloping om an un o eseeable
e en wi h ega d o ne wo k load (Liao e al. 2004). This
app oach is based on he phase ansi ions o he p ob-
abili y o cascading ailu es, e i ied expe imen ally us-
ing lowe and highe esolu ion ne wo ks. Bo h ypes o
ne wo k demons a e phase ansi ions. The esul s o he
expe imen con i med a a ian whe e he cascade ailu e
isk assessmen is based on a sea ch nea he cu en op-
e a ing poin o he phase ansi ion o he p obabili y o
cascading impac s.
The me hod o s udy cascading e ec s (Hassel e al.
2014) deals wi h he na u e and p ocesses o cascading
impac s. The au ho s poin ou ha unde s anding he
p ocesses o cascading impac s can help add ess and
mi iga e hei e ec s. A he same ime, hey p esen a
me hodology designed o cha ac e ize and analyse hese
impac s. In he desc ip ion, hey d aw on inpu da a om
he analyses o eme gencies ha ha e al eady happened in
he pas . They also examine he condi ions ha con ib-
u e o he de e io a ion o he ex en o cascading impac s
and o he condi ions ha educe he e ec s o cascading
impac s. The p esen ed me hod is based on a concep ual
model o cascading impac s, which comp ises h ee basic
s eps. The i s is iden i ying a dis up ed (dependen ) sys-
em, speci ically whe he his sys em is di ec ly a ec ed by
he ini ia ion e en o is indi ec ly in luenced h ough a
link o he in luencing sys em. The second s ep is desc ib-
ing he impac s on all o he dis up ed sys ems in o de o
unde s and how and o wha ex en a dependen sys em
is in luenced by an in luencing sys em. The las s ep ex-
amines he impac sys em a ge ing all dependen sys ems
a ec ed by he ini ia ion e en .
In he ollowing yea s, a comp ehensi e me hodol-
ogy based on eliabili y me hods was in oduced o au-
oma ically gene a e scena ios du ing c i ical in as uc-
u e ailu es wi h subsequen cascading impac s (Gonz a
e al. 2016). In hei s udy, he au ho s p esen ed exis -
ing me hods o assessing in e dependencies in he c i i-
cal in as uc u e sys em wi h a ocus on assessing hei
eliabili y. In he case s udy, hey assessed he cascading
impac s be ween elec ici y and ail anspo . This as-
sessmen was based on he use o he aul ee analysis
(IEC 61025:2006) and ailu e mode and e ec s analysis
(IEC 60812:2006) me hods.
An app op ia e me hod o assessing cascading impac s
is an app oach based on e alua ing echnical sys ems
(Renge e al. 2017). Sys em e alua ion heo y applies bo h
sys emic hinking and sys em heo y. Using h ee s eps, an
e alua o can (1) de ine he sys em, (2) e alua e sys em e -
iciency, (3) e alua e sys em e ec i eness. The au ho s also
s a e ha he e ec i eness o a sys em depends on p omp ,
su icien ly equen , speci ic, ele an and eliable sha -
ing o in o ma ion a and be ween sub-sys ems h ough
eedback mechanisms, i.e., eedback in he con ex o he
sub-sys em o be ween indi idual sub-sys ems.
Ano he possible iew o he issue in ques ion is o -
e ed in he esea ch by Chen and Milano ić (2017).
The au ho s p esen ed selec ed me hods o modelling
and simula ions designed o analyse in as uc u e in e -
dependencies on models based on a ac o o so-called
agen . These a e mos o en used because o he de ailed
depic ion o sys em beha iou . In his model, he unde -
lying elemen o agen is designed o p o ide a pa icula
se ice and ollows a se ies o “wha i ” ules and p ede-
ined a ibu es, making i possible o lea n and espond
acco dingly.
Zucca o e al. (2018) desc ibed he possibili y o ex-
ao dina y e en s occu ing o assessed elemen s in
which mul iple e en s may ac simul aneously on one
elemen . This phenomenon can signi ican ly a ec he
sp ead o impac s by cascading e ec s. I also has o be
ca e ully assessed in e ms o eme gency planning and
managemen . The a icle discusses, om a heo e ical
poin o iew, he needs o modelling and he main issues
o conside a ion when simula ion ools a e de eloped
ha aim o inco po a e he analyses o cascading impac s
and e ec i ely suppo s akeholde s in hei p epa a ions
o sol e and mi iga e hei consequences h ough plan-
ning a local, na ional and in e na ional le els. The aim o
his model is o desc ibe scena ios o sp eading cascading
impac s a di e en le els acco ding o he a ailabili y o
da a o di e en ca ego ies o elemen s and models o
di e en sou ces o isk.
The inal cu en ool is he CIA me hod, which was
de eloped o quan i y he sp ead o cascading impac s in
c i ical in as uc u e sys em (Rehak e al. 2018). The basis
o he e alua ion p ocess is o mula ing a s a ic s ochas ic
model o c i ical in as uc u e elemen s and he depend-
304 D. Rehak e al. Iden i ying c i ical elemen s o oad in as uc u e using cascading impac assessmen
encies be ween hem. This model is based on p edic ing
he pe cen age o p obabili y and he impac in ensi y.
This me hod assesses all elemen s ound in a selec ed
a ea and e alua es hei esilience (NIAC 2009) and links
(Rinaldi e al. 2001). A s uc u al map o he isk o he
sp ead o cascading impac s can hen be c ea ed. E alu-
a ion o he isk o sp eading cascading impac s is based
on h ee limi ing ac o s: (1) he in ensi y o he ini ia ion
h ea (i.e., he d op in he le el o se ice deli e y om
he p e ious sec o ), (2) he le el o esilience o he de-
penden b anches, (3) he in ensi y o he link be ween he
e alua ed b anches.
3. Me hod o ICERI
P uden iden i ica ion o c i ical elemen s allows hei
esilience o be acco dingly e alua ed (e.g., Rehak e al.
2019a; Nan, Sansa ini 2017; Be occhi e al. 2016). Weak-
nesses can be iden i ied and e oac i ely s eng hened
(e.g., Public Sa e y Canada 2018; Labaka e  al. 2015).
Howe e , no sui able me hod o comp ehensi ely iden-
i ying elemen s o all linea , poin and a eal opological
s uc u es is cu en ly a ailable (Sli ko a e al. 2018). Fo
his eason, he au ho s o he a icle p opose he ICERI
me hod, which was c ea ed speci ically o iden i y c i ical
elemen s o oad in as uc u e.
This me hod analyses he sp ead o impac s o po en-
ially dis up ed oad in as uc u e elemen s in o depend-
en and in luenced elemen s in he c i ical in as uc u e
sys em – bo h inside and ou side he oad anspo
sub-sec o (e.g., impac s on elec ici y supply, heal hca e
acili ies, in eg a ed escue sys ems, se ices and indus-
y). This analysis is based on p og essi ely e alua ing he
pe meabili y o impac s be ween hose elemen s whose
dependence o in luence has been iden i ied (Rehak, No-
o ny 2016). The isk o sp ead o cascading impac s is
hen e alua ed o hese elemen s h ough he in ensi y
o hei links and he le el o esilience in indi idual ele-
men s. This e alua ion is pe o med om a mac oscopic
poin o iew, i.e., whole componen s o he sys em a e
examined, ega dless o hei de ailed s uc u e.
3.1. F amewo k o he ICERI me hod
ICERI using CIA is a ela i ely demanding p ocess ha
equi es a clea ly de ined amewo k. This amewo k
consis s o ou basic a eas: (1) elemen s o oad in a-
s uc u e, (2) h ea s o oad in as uc u e elemen s, (3)
dependen and in luenced c i ical in as uc u e elemen s,
(4) me hodology (Figu e 2).
The basic a eas o iden i ying c i ical elemen s a e in
he oad in as uc u e elemen s hemsel es. These can be
classi ied in o h ee basic g oups acco ding o hei opo-
logical s uc u e (Sli ko a e al. 2018): (1) linea elemen s
(e.g., mo o ways and oads), (2) poin elemen s (e.g.,
b idges and unnels), (3) a ea elemen s (e.g., bus s a ions).
The c i icali y o hese elemen s can be assessed no only
in he oad anspo sub-sec o bu also in o he ele an
c i ical in as uc u e sub-sec o s (e.g., ail anspo , he
in eg a ed escue sys em, elec ici y supply).
An assessmen o cascading impac s can only be con-
duc ed in ela ion o speci ic h ea s ha may cause dis-
up ion o o he ailu e o oad in as uc u e elemen s
(Pa man e  al. 2019). To his end, eigh basic h ea
g oups we e de ined (Table 1) based on he pe il e en
ypology (IRDR 2014), which is used in la ge-scale e en
da abases. F om hese e en s, only hose h ea s in which
he ocus was p ima ily on in as uc u e we e selec ed.
As wi h classi ying h ea s ha a ec oad in as uc-
u e elemen s, c i ical in as uc u e elemen s dependen
on o a ec ed by oad in as uc u e elemen s also ha e
o be classi ied. The i s g oup comp ises dependen ele-
men s ha canno unc ion wi hou oad in as uc u e
elemen s. These elemen s occu no only in he anspo
sec o (e.g., mo o way dependency on a mo o way b idge
o unnel) bu also in o he c i ical in as uc u e sec o s
(e.g., he in eg a ed escue sys em’s dependence on oad
in as uc u e). The second g oup comp ises elemen s
whose unc ion may be a ec ed by he dis up ion o o
ailu e o oad anspo elemen s. Again, hese elemen s
no only occu in he anspo sec o (e.g., he e ec o
mo o way ailu e on he su ounding oads) bu also in
o he sec o s o c i ical in as uc u e (e.g., he impac o
oad ailu es on heal hca e se ices o elec ici y supply).
Figu e 2. F amewo k o ICERI me hod
Me hods o iden i ying
dependen elemen s
Me hods o assessing he esilience
o c i ical in as uc u e elemen s
Me hods o assessing
he in ensi y o links
Elemen s o he oad anspo sub-sec o
Elemen s o he anspo sec o
Elemen s o he c i ical in as uc u e sys em
Na u ogenic h ea s
An h opogenic h ea
s
Technogenic h ea s
Linea elemen s
Poin elemen
A eal elemen s
Elemen s o oad
in as uc u e
Me hodology
Dependen and in luenced
elemen s o c i ical
in as uc u e
Th ea s ac ing on elemen s
o oad in as uc u e
Iden i ying C i ical Elemen s
o Road In as uc u e
(ICERI)

T anspo , 2020, 35(3): 300–314 305
The mos impo an pa o he amewo k o he
ICERI me hod is he me hodology o ming he s a -
ing poin o p oposing he p ocedu e o applying o
his me hod. The me hodology includes h ee impo an
me hod g oups, which a e:
– me hods sui able o iden i ying dependen and
in luenced elemen s, such as e en ee analysis
(IEC 62502:2010) o aul ee analysis (IEC 61025:2006),
– C i ical In as uc u e Elemen s Resilience Assessmen
(CIERA) me hods, such as he complex app oach o
assessing c i ical in as uc u e elemen s (Rehak e al.
2019a) o he guidelines o c i ical in as uc u e esil-
ience e alua ion (Be occhi e al. 2016),
– me hods o iden i ying and assessing he in ensi y o
links (e.g., Seppänen e al. 2018; Gonz a e al. 2016;
Min e al. 2007).
3.2. P ocedu e o he ICERI me hod
The abo e amewo k allows a p ocedu e o ICERI o be
de ined. The s uc u e o his p ocedu e is based no only
on gene al me hods (e.g., IEC 31010:2019) bu also on
speci ic me hods ha assess c i ical elemen s in simila
ields (e.g., Sli ko a e al. 2018; Lei ne e al. 2017; Pan
e al. 2016). A p ocedu e o applying he ICERI me hod
was de eloped om hese backg ound ma e ials and com-
p ises eigh consecu i e s eps (Figu e 3).
The s a ing poin in ICERI is delimi ing he e i o y
unde e alua ion (S ep 1). Selec ing he e i o y is no
limi ed by any hing, howe e , selec ing smalle e i o ial
uni s is ecommended because o ime cons ain s. I a
la ge e i o ial uni is e alua ed, di iding i in o se e al
smalle pa s is ecommended. In his case, he occu ence
o links be ween he elemen s o he indi idual pa s mus
also be checked unde he e alua ion p ocedu e.
This is ollowed by selec ing he oad in as uc u e
ini ia o s (S ep 2) loca ed in he gi en e i o y. These
a e assessed agains he speci ic, p edic ed h ea (see he
ICERI amewo k). Ini ia ing elemen s a e oad in a-
s uc u e elemen s ha a e subsequen ly assessed o he
isk o sp eading cascading e ec s when he elemen is
dis up ed o ails. The elemen s wi h he highes le el o
isk a e hen designa ed as c i ical elemen s. These ele-
men s can be selec ed ei he acco ding o documen a ion
om he ele an au ho i ies (e.g., Minis y o T anspo
o he Czech Republic) o h ough app op ia e me h-
ods (e.g., Lei ne e al. 2018; D ořák e al. 2017), such
as he S eng hs, Weaknesses, Oppo uni ies and Th ea s
(SWOT) analysis me hod (Weih ich 1982). This me hod is
ecommended and may be used o iden i y weaknesses in
elemen s and any ex e nal h ea s. Mainly, he highes p i-
o i y elemen s o he “a oid” s a egy should be e alua ed.
The nex s ep in applying he ICERI me hod is se-
lec ing elemen s ha depend on ini ia ing elemen s and
any elemen s ha may be a ec ed by hei dis up ion o
ailu e (S ep 3). Selec ing elemen s is conduc ed in wo
s ages. In he i s s age, he sec o s o in e es and sub-
sec o s o c i ical in as uc u e (e.g., elec ici y, medical
acili ies o in eg a ed escue sys em) a e selec ed a he
disc e ion o he e alua o . In he second s age, dependen
o in luenced c i ical in as uc u e elemen s in hese sec-
o s and sub-sec o s a e selec ed. Selec ing hese elemen s
is based on iden i ying links be ween hese elemen s and
he ini ia ing elemen s, wi h an emphasis on dependence
and in luence (Rehak, No o ny 2016). Me hods sui able
o iden i ying and e alua ing link in ensi ies may be used
o his pu pose (e.g., Seppänen e al. 2018; Gonz a e al.
2016; Min e al. 2007).
A e selec ing he ini ia ing, dependen and in luenced
elemen s, a s uc u al map o cascading impac s can be
c ea ed (S ep 4). Fo his pu pose, he e en ee analysis
(IEC 62502:2010) me hod is sui able. This me hod is used
o analyse e en s ha may lead o a po en ial acciden . In
he e alua ion, he e alua o hypo hesizes “wha i ”, and
in his manne sea ches o e en s ha could po en ially
a ise a e an ini ia ion e en . F om his e alua ion s age,
a s uc u al map o he dis ibu ion o cascading e ec s
be ween elemen s can be compiled and hen quan i ied
(Figu e 4).
Table 1. Classi ica ion o h ea s o assessing cascading e ec s in c i ical in as uc u e sys em
Na u ogenic h ea s Technogenic h ea s An h opogenic h ea s
In e nal h ea s – p ocedu al- echnological pe sonnel
Ex e nal h ea s me eo ological cascading cybe ne ic
geological physical
Figu e 3. P ocedu e o applying he ICERI me hod
Delimi ing he assessed e i o y
Selec ing ini ia ing elemen s o oad in as uc u e
Selec ing dependen and in luenced elemen s o c i ical in as uc u e
C ea ing a s uc u al map o cascading impac s
De e mining he link in ensi y be ween he e alua ed elemen s
De e mining he le el o esilience o e alua ed elemen s
De e mining he isk le el o cascading impac s
Iden i ying C i ical Elemen s o Road In as uc u e (ICERI)
1
2
3
4
5
6
7
8
S eps
306 D. Rehak e al. Iden i ying c i ical elemen s o oad in as uc u e using cascading impac assessmen
Fo hose elemen s be ween which a link has been
iden i ied, he in ensi y o his link is subsequen ly de e -
mined (S ep 5). The in ensi y o he link is no only de e -
mined be ween he ini ia ing elemen and i s dependen
elemen s in he oad anspo sec o bu also be ween
dependen elemen s. The link in ensi y is measu ed ac-
co ding o he ollowing c i e ia: (1) ype o link, (2) s a e
o link, (3) le el o link, (4) subs i u ion o link, (5) em-
po al cha ac e o he link, (6) s uc u e o he link. The
poin sco e alues o each c i e ia (i.e., 1– c i e ion wi h
a low-le el link, 2– c i e ion wi h a mid-le el link, 3–
c i e ion wi h a high-le el link) we e es ablished using he
pai compa ison me hod (Da id 1988) and a e p esen ed
in Table 2.
The c i e ia de e mining link in ensi y di e in hei
signi icance du ing e alua ion. Fo his eason, no mal-
ized weigh s we e de ined o hese c i e ia (Table 3). The
no malized weigh s we e de ined using he pai compa i-
son me hod (Da id 1988).
The inal calcula ion o link in ensi y be ween elemen s
is calcula ed om a weigh ed a e age acco ding o Equa-
ion (1):
max
1
100
n
iii
i
IL C w C
=
= ⋅⋅
∑
, (1)
whe e: IL– in ensi y o he link be ween he e alua ed ele-
men s [%]; Ci– poin alue o he i- h c i e ia; n– numbe
o c i e ia; wi– no malized weigh o he i- h c i e ia [%];
max
i
C
– maximum poin alue o he i- h c i e ia.
The nex s ep in he p ocedu e o ICERI is de e min-
ing he le el o esilience o he elemen s unde assess-
men (S ep 6). The CIERA me hod (Rehak e al. 2019a)
is ecommended o his, as i pe mi s he echnical and
o ganiza ional esilience o elemen s o be comp ehen-
si ely assessed and hei weaknesses iden i ied in o de
o s eng hen hei esilience. The a iables o esilience
e alua ion can be ca ego ized in o h ee g oups acco d-
ing o he esilience de e mining componen s: obus ness,
eco e abili y and adap abili y (NIAC 2009). An o e iew
o hese a iables is p esen ed in Table4.
The poin alues o indi idual c i e ia and he p ocess
o assigning hem a e desc ibed in de ail in he CIERA
me hod (Rehak e al. 2019a). The inal calcula ion o e-
silience le el o he elemen s is calcula ed acco ding o
Equa ion(2):
1 11
11
n nm
j kk
j jk
RE K V w
nn
= = =
=⋅=⋅ ⋅
∑ ∑∑
, (2)
whe e: RE– c i ical in as uc u e elemen esilience [%];
Kj– j- h c i ical in as uc u e elemen esilience com-
ponen [%]; n– o al numbe o esilience de e mining
componen s; Vk– he k- h c i ical in as uc u e elemen
esilience a iable [%]; wk– k- h no malized weigh o he
k- h a iable esilience o he c i ical in as uc u e ele-
men
0; 1


; m– o al numbe o a iables in he j- h
componen .
F om he link in ensi y assessmen and elemen esil-
ience le els, he isk le el o he sp ead o cascading im-
pac s can hen be de e mined (S ep 7). This isk is always
assessed sepa a ely in each pai o elemen s. The assess-
men ’s s a ing poin is he gene al ela ionship whe e he
Figu e 4. Gene al depic ion o a s uc u al map o he sp ead o cascading impac s
Dependen elemen o he
in eg a ed escue sys em
In luenced elemen o
he elec ici y supply
Ini ia o elemen 1
o he oad in as uc u e
Dependen elemen 1
o he oad in as uc u e
In luenced elemen
o he oad in as uc u e
P esump i e h ea
Dependen elemen 2
o he oad in as uc u e
In luenced elemen
o he chemical indus y
Ini ia o elemen 2
o he oad in as uc u e
Table 2. Poin alues o he c i e ia de e mining link in ensi y
C i e ia de e mining link in ensi y CiPoin alue
Type o link
(Rinaldi e al. 2001)
physical link 3
geospa ial link 2
cybe ne ic link 2
logical link 1
S a e o link
(Rehak and No o ny
2016)
mu ual dependence 3
dependence 2
in luence 1
Le el o link
(Rehak e al. 2016)
sys em link 3
sec o link 2
sub-sec o link 1
Subs i u ion o link
no subs i u e link exis s 3
only one subs i u e link
exis s 2
wo o mo e subs i u e
links exis 1
Tempo al
cha ac e is ic link
unin e up ed 3
pe iodic 2
s and-by 1
S uc u e o link
di ec 3
indi ec ac oss one node 2
indi ec ac oss wo o
mo e nodes 1
T anspo , 2020, 35(3): 300–314 307
isk is exp essed by a combina ion o he p obabili y o
occu ence o an undesi able e en and i s impac le el
(IEC 31010:2019). The p obabili y o occu ence o cas-
cading impac s, in his case, is de e mined by he link in-
ensi y IL. The cascading impac le el is de e mined by he
esilience o he e alua ed elemen s RE. Highe esilience
means ad e se impac s a e minimized because he ulne -
abili y o hese elemen s, which acili a es he sp ead o
cascading impac s, is also minimized.
F om he abo e, Equa ion (3) was de i ed o calcula e
he isk o a cascading impac sp eading du ing dis up ion
o o ailu e o oad in as uc u e elemen s:
3
IE DE
R V V IL= ⋅ ⋅=
( ) ( )
311
IE DE
RE RE IL− ⋅− ⋅
, (3)
whe e: R– le el o isk o a sp eading cascading impac [%];
VIE– ulne abili y o he in luencing elemen [%]; VDE–
ulne abili y o he dependen elemen [%]; REIE– le el o
esilience o he in luencing elemen [%]; REDE– le el o
esilience o he dependen elemen [%]; IL– link in en-
si y be ween he in luencing and dependen elemen [%].
The inal s ep in he applying he ICERI me hod is
iden i ying he c i ical elemen s o oad in as uc u e
(S ep 8). This is done using he esul s om he isk le el
assessmen o cascading e ec s sp eading be ween ele-
men s. These alues a e included in he s uc u al map
and hen compa ed wi h e e ence alues in o de o ca -
ego ize he le el o sp ead o cascading impac s (Table 5).
The ca ego iza ion o cascading e ec le els and e e -
ence alues is philosophically based on he ailu e mode,
e ec s and c i icali y analysis (IEC 60812:2006). This
me hod uses mul iple a iables o de e mine isk le el
and is based on a ia ions in ex eme alues when e alu-
a ing s a es. Indi idual le els o c i icali y ha ac o in
ex eme alue a ia ion in he ou -s age e alua ion scale
we e de e mined in a manne simila o he me hod o
assessing he c i icali y o ailway in as uc u e elemen s
(Sli ko á 2018):
– 1,1,1,4=> ⌀ 1.75=> 43.7%;
– 1,1,4,4=> ⌀ 2.50=> 62.5%;
– 1,4,4,4=> ⌀ 3.25=> 81.3%;
– 4,4,4,4=> ⌀ 4.00=> 100%.
The inal iden i ica ion o c i ical elemen s o oad in-
as uc u e is achie ed using he e e ence alues o ca e-
go izing hele el o sp ead o cascading impac s (Table 5).
Elemen s demons a ing a c i ical isk le el (i.e., Ca ego-
y I) be ween each o he a e subsequen ly designa ed as
c i ical. Weaknesses should be iden i ied in hese elemen s
and adequa e sa e y measu es hen in oduced in o de o
educe link in ensi y and inc ease esilience (e.g., Š olle
e al. 2018; Klein, Hu e 2017; Labaka e al. 2015; H o-
mada, Lukas 2012). A en ion should also be gi en o ele-
men s demons a ing a high le el o isk (i.e., Ca ego y II)
be ween each o he . In all o he elemen s, signi ican p o-
li e a ion o cascading impac s is no o eseen.
Table 4. Va iables de e mining he esilience o c i ical
in as uc u e elemen s (Rehak e al. 2019a)
Resilience componen s
o c i ical in as uc u e
elemen s Ki
Va iables o assessing
esilience Vj
Robus ness
c isis p epa edness
edundancy
de ec ion abili y
esponsi eness
physical esilience
Reco e abili y
ma e ial esou ces
inancial esou ces
human esou ces
eco e y p ocess
Adap abili y
isk managemen
inno a ion p ocesses
educa ional and de elopmen
p ocesses
Table 3. No malized weigh s o c i e ia de e mining link in ensi y
C i e ia Type
o link
S a e
o link
Le el
o link
Subs i u ion
o link
Tempo al cha ac e
o link
S uc u e
o link S
Weigh coe icien s 29% 24% 19% 14% 10% 4% 100%
Table 5. Re e ence alues o ca ego izing he le el o sp ead o
cascading impac s
In e al Risk le el o
sp eading Desc ip ion
(
81;100 Ca ego y I
C i ical isk le el o he sp ead
o cascading impac s.
The esul o such cascading
impac s may be he ailu e
o a dependen elemen
(
62; 81
Ca ego y II
High- isk le el o he sp ead
o cascading impac s.
The esul o such cascading
impac s may be signi ican
dis up ion o he unc ioning
o a dependen elemen
(
43; 62
Ca ego y III
Accep able isk le el o he sp ead
o cascading impac s.
The esul o such cascading
impac s may be pa ial dis up ion
o o limi ed unc ioning
o a dependen elemen
0; 43 Ca ego y IV
Low isk le el o he sp ead
o cascading impac s.
This ype o cascading impac
will no esul in dis up ion o o
limi ed unc ioning
o a dependen elemen
308 D. Rehak e al. Iden i ying c i ical elemen s o oad in as uc u e using cascading impac assessmen
4. Case s udies in applying he ICERI me hod
The p ac ical applica ion o he ICERI me hod is p esen -
ed as a case s udy o demons a e he sequen ial e alua-
ion o selec ed elemen s in eigh consecu i e s eps (see
below). The esul s ob ained we e subsequen ly discussed
wi h s akeholde s (i.e., Minis y o T anspo o he Czech
Republic, Czech Road and Mo o way Di ec o a e, Czech
Railway and T a ic Rou e Adminis a ion, Regional Au-
ho i y o he Mo a ian–Silesian Region, Eme gency Med-
ical Se ice o he Mo a ian–Silesian Region). The au hen-
ici y and p edic i e alue o he esul s we e con i med.
S ep 1: Delimi ing he assessed e i o y. The s a ing
poin in ICERI is delimi ing he e i o y unde assess-
men . In o de o es he ICERI me hod, he sou h-wes -
e n pa o he ci y o Os a a was selec ed. Asigni ican
numbe o impo an elemen s o anspo in as uc u e
a e ound in his ci y. Os a a is loca ed in he no heas -
e n pa o he Czech Republic and is an impo an oad
and ail anspo hub o Slo akia and Poland.
S ep 2: Selec ing ini ia ing elemen s o oad in a-
s uc u e. The nex s ep in ol ed selec ing he oad in-
as uc u e ini ia o s loca ed in he gi en e i o y. These
we e assessed agains he speci ic, p edic ed h ea (see
ICERI amewo k). Because o he case s udy’s scale, only
one oad in as uc u e elemen was selec ed, namely he
in e change o he D1 Mo o way and Exp essway 11 (Fig-
u e5). This ini ia o elemen was selec ed using he as-
sessmen o c i ical in as uc u e elemen s in anspo
me hod (D ořák e al. 2017). The po en ial isk o his
elemen collapsing due o he use o inapp op ia e back-
g ound ma e ials (RSD 2012) was conside ed. Fo his ea-
son, he ini ia o was e alua ed in e ms o he isk c ea ed
by poo echnical condi ion.
S ep 3: Selec ing dependen and in luenced elemen s
o c i ical in as uc u e. The nex s ep in applying he
ICERI me hod was selec ing elemen s ha may be ad-
e sely a ec ed by dis up ion o o ailu e o he ini ia o
elemen . Selec ing hese elemen s was conduc ed in wo
s ages. In he i s s age, he ele an c i ical in as uc u e
sub-sec o s we e selec ed, speci ically oad anspo , ail
anspo and he in eg a ed escue sys em. In he second
s age, he dependen and in luenced elemen s o c i ical
in as uc u e in hese sub-sec o s we e selec ed. These
elemen s we e iden i ied om he links be ween hese el-
emen s and he ini ia ing elemen , wi h an emphasis on
dependence and in luence (Rehak, No o ny 2016). F om
his, a o al o ou elemen s we e selec ed, which a e
shown in Figu e 5.
Two dependen elemen s and wo in luenced elemen s
we e iden i ied om he abo e map backg ound. Exp ess-
way 11 and he in eg a ed escue sys em (speci ically he
eme gency medical se ices) a e elemen s dependen on
he lyo e in e sec ion. The exp essway acili a es ans-
po a ion o pa ien s om he Os a a–Jih and Zábřeh dis-
ic s o he hospi al in Po uba (see op le ). I he unc-
ioning o he lyo e in e sec ion ails (in he con ex o
he selec ed h ea , his would be he s uc u e collapsing),
a ic on he D1 Mo o way and he high-speed ailway
co ido would be a ec ed.
S ep 4: C ea ing a s uc u al map o cascading im-
pac s. Based on he selec ed ini ia o and dependen and
in luenced elemen s, a s uc u al map o he cascading im-
pac s was c ea ed (Figu e6). Fo his pu pose, he e en
ee analysis me hod (IEC 62502:2010) was used in o de
o analyse e en s ha may lead o a po en ial acciden .
S ep 5: De e mining he link in ensi y be ween he
e alua ed elemen s. The in ensi y o he links be ween
elemen s sha ing a link was hen measu ed. In ensi y was
e alua ed acco ding o he de e mining c i e ia (Table 2)
and hen calcula ed acco ding o Equa ion (1). The esul -
ing alues o link in ensi y be ween indi idual co ela ed
elemen s a e p esen ed in Table 6.
Figu e 5. The selec ed elemen s plo ed on a map backg ound
ini ia o elemen
dependen elemen o oad in as uc u e
in luenced elemen o oad in as uc u e
in luenced elemen o ailway in as uc u e
dependen elemen o in eg a ed escue sys em