Jou nal o Enginee ing Science Vol. XXXII, no. 2 (2025), pp. 7 - 25
Fascicle Indus ial Enginee ing ISSN 2587-3474
Topic Applied Enginee ing Sciences and Managemen eISSN 2587-3482
Jou nal o Enginee ing Science June, 2025, Vol. XXXII (2)
h ps://doi.o g/10.52326/jes.u m.2025.32(2).01
UDC 656.11.053.3
ROUNDABOUT – ELEMENT OF SAFETY, ECOLOGY AND ECONOMY
Oli ian Pădu e *, ORCID: 0000-0002-6024-3763,
Vasile Plămădeală, ORCID ID: 0000-0003-1722-2649,
Vladimi Goian, ORCID: 0000-0002-0031-0389
Technical Uni e si y o Moldo a, 168 S e an cel Ma e Bl d., Chisinau, Republic o Moldo a
* Co esponding au ho : Oli ian Pădu e, oli ian.padu e@ an.u m.md
Recei ed: 05. 15. 2025
Accep ed: 06. 12. 2025
Abs ac . S a is ical analysis ein o ces he conclusion ha oad acciden s a e no andom
and e en mo e unp edic able o una oidable, al hough hei occu ence is andom. The
concen a ion o oad acciden s a in e sec ions is high, a ound 25-30% o he o al numbe
o oad acciden s. The in e sec ion i sel is an a ea o concen a ion o con lic poin s, whe e
he occu ence o oad acciden s is bo h heo e ically and p ac ically possible due o he
con ac o ehicle lows om h ee di e en di ec ions: in e sec ing, sepa a ing and me ging.
Inc easing he sa e y o in e sec ions he e o e boils down o aking measu es o educe he
numbe o con lic poin s and he deg ee o hei po en ial dange . The a icle desc ibes he
pu pose, ad an ages and disad an ages, con lic poin s, classi ica ion and ypes o
oundabou s. The bene i s o oundabou o ganiza ion in e ms o oad a ic sa e y,
en i onmen al sa e y and inc easing he oad's passing capaci y, hus educing wai ing ime
a in e sec ions, a e also analyzed.
Keywo ds: oundabou , in e sec ion, con lic poin s, oad acciden s, oad a ic sa e y,
en i onmen al sa e y, oundabou capaci y.
Rezuma . Analizele s a is ice în ă esc concluzia, că acciden ele u ie e nu sun în âmplă oa e
şi cu a â mai mul imp e izibile sau ine i abile, cu oa e că apa iţia lo es e alea oa e.
Concen ația acciden elo u ie e la in e secții es e una ma e, ci ca 25-30% din numă ul o al
de acciden e de ci culație. In e secția p ezin ă în sine o zonă de concen a e a punc elo de
con lic , unde apa iția acciden ului u ie a â eo e ic, câ și p ac ic es e posibilă da o i ă
con ac ului luxu ilo de ehicule din ei di ecții di e i e: de in e sec a e, sepa a e și
uziona e. P in u ma e, c eș e ea sigu anței in e secțiilo se educe la în ep inde ea uno
măsu i de educe e a numă ului punc elo de con lic și g adului de pe icol po ențial al
aces o a. În a icol sun desc ise des inația, a an ajele și deza an ajele, punc ele de con lic ,
clasi ica ea și ipu ile de sensu i gi a o ii. De asemenea, sun analiza e bene iciile o ganiză ii
sensului gi a o iu p i ind sigu anța a icului u ie , secu i a ea ecologică și idica ea
capaci ății de ece e a d umului, as el educând impul de aș ep a e la in e secții.
Cu in e cheie: sens gi a o iu, in e secție, punc e de con lic , acciden e u ie e, sigu anța ci culației
u ie e, sigu anța ecologică, capaci a e de ece e a in e secției.
8 O. Pădu e, V. Plămădeală, V. Goian
Jou nal o Enginee ing Science June 2025, Vol. XXXII (2)
1. In oduc ion
In global oad a ic managemen p ac ices, one o he mos e ec i e me hods o
educing a ic acciden s is conside ed o be oundabou in e sec ions [1]. In many coun ies
in Wes e n Eu ope, No h Ame ica and Aus alia, he e ec i eness o using oundabou s is
con incingly con i med by he educ ion o all c ash indica o s, in pa icula by he educ ion
in c ash se e i y and he dec ease in he numbe o oad a ic acciden s wi h a ali ies.
Roundabou in e sec ion o oundabou is he in e sec ion, whe e app oaching ehicles
decele a e and begin o ci cle a ound he cen al „island” coun e clockwise on oads wi h
a ic on he igh side o he oad, o clockwise on oads wi h a ic on he le side o he
oad, un il exi ing on o a oundabou a e ial (con e gence) [2].
Roundabou s a e in e sec ions o med by a one-way ci cula pa h a ound a cen al
island. Thus, he oundabou can be compa ed as a one-way oad wi h a sequence o
T-in e sec ions (Figu e 1) [3-5].
Figu e 1. Roundabou in e sec ion shown as a one-way oad
wi h a sequence o T-junc ions [3,4].
In he li e a u e, oundabou s a e a ached o a b oad class o ci cula oad junc ions
(ci cula in e sec ions). Howe e , no e e y ci cula oad junc ion is conside ed o be a
oundabou . The e a e h ee ypes o ci cula oad junc ions [1].
Ro a ies a e an old ype o ci cula oad junc ions, cha ac e ized by a la ge diame e ,
some imes exceeding 100 m. The la ge diame e is due o he high p ojec ed a ic speeds,
which exceed 50 km/h. Such junc ions p o ide a sligh de ia ion om linea a ic and may
ope a e acco ding o he „ igh obs uc ion” ule (in coun ies wi h igh -hand a ic), i.e. a ic
en e ing he ci cle has p io i y o e a ic mo ing in he ci cle.
Neighbo hood a ic ci cles a e ci cula oad junc ions usually loca ed on local s ee s
in esiden ial a eas o a ic calming. The en ances o such junc ions may be undi ec ed o
accompanied by signs and oad ma kings, which indica e he p io i y o a ic on he ci cle.
Such in e sec ions a e usually no accompanied by low channeliza ion (i.e. no sepa a ion
islands a e c ea ed a he en ance along he oadway axis). La ely, his ype o oundabou
in e sec ion is becoming mo e widesp ead and is used as a means o a ic calming.
Roundabou s a e ci cula oad nodes wi h es ablished geome ical pa ame e s and
o m o o ganiza ion o he low o oad a ic, including [1]:
• „Yield” o „Manda o y s op” oad signs a ci cle en ances [6];
• geome y o he in e sec ion in plan – adii o he oadway side o he ci cle, o he
unimmedia e en ances o and exi s om he oadway side o he ci cle, o he app oaches o
he in e sec ion, which do no allow he de elopmen o a speed g ea e han 50 km/h;
• manda o y canaliza ion o oad lows a he en ances o he ci cle, while he
sepa a ion islands a he en ances a e used as sa e y islands o pedes ians.
Roundabou – elemen o sa e y, ecology and economy 9
Jou nal o Enginee ing Science June, 2025, Vol. XXXII (2)
The e m oundabou s o igina ed in he Uni ed Kingdom as ea ly as 1929 wi h he
Minis y o T anspo a ion and he Ins i u e o Town and Coun y Planning. I should be no ed
ha Flo ida's Roundabou In e sec ion Guidelines (FRG 1996) in oduced a new e m „mode n
oundabou ”, which has come o be commonly used in echnical li e a u e.
The i s oundabou was o ganized in Pa is a ound he A c de T iomphe in 1901.
Columbus Ci cle in New Yo k was buil in 1904. The i s B i ish oundabou ollowed in 1909
(Le chwo h Ga den Ci y) – o iginally planned as a pedes ian island. La e , du ing 1925-1926
in he UK, se e al oundabou in e sec ions we e buil in di e en pa s o London. A ha
ime, when designing in e sec ions, hey we e guided only by accumula ed expe ience and
in ui ion. Widesp ead use began in he mid-1960s, when English enginee s pe ec ed he
sys em o guiding he low o ca s [1].
In ac , in 1966, he UK adop ed a new p io i y ule – he main oad low mo ing
a ound he ci cle has p io i y o e he main oad low en e ing he ci cle. Wi h he
in oduc ion o his inno a ion (modi ica ion) o oundabou s, he h ough capaci y (by
10-40%, acco ding o a s udy by he Road Resea ch Labo a o y) and a ic sa e y le els
inc eased signi ican ly. The success o he in oduc ion o mode n oundabou s has e i ed
in e es in his ype o in e sec ions wo ldwide, especially in Eu ope.
Since he la e 1980s, oundabou s ha e become a widesp ead solu ion o oad
in e sec ions in se e al coun ies, including he Ne he lands, No way, F ance, Swi ze land,
Sweden, Swi ze land, he Uni ed S a es o Ame ica, Aus alia e c. In he Ne he lands, abou
400 oundabou s we e buil in jus six yea s, due o hei ad an ages such as educed
acciden s and he absence o he need o a ic ligh s. In No way, he numbe inc eased
signi ican ly be ween 1990 and 1992, eaching 500 oundabou in e sec ions. F ance has
seen a apid inc ease, eaching abou 12080 oundabou s a he end o 1994 and mo e han
27000 in 2005. In Sweden, he e has been a signi ican inc ease in he numbe o oundabou s
(mo e han 1000 in 2000), wi h s udies showing ha single-lane ci cles wi h a cen al island
diame e o 10 o 20 m a e he sa es , educing speed and acciden s, especially hose
in ol ing cyclis s. The Uni ed S a es began building mode n oundabou s in he 1990s wi h
excellen esul s in educing acciden s, and by 2002 he numbe had exceeded 600. In he
mean ime, oundabou s ha e become e y popula in many coun ies. In Aus alia, o
example, he numbe has isen o o e 10000, in he UK o o e 25000 and in F ance o o e
32000 [7].
A busy in e sec ions, wai ing imes o yielding anspo a ion can be qui e long. This
would c ea e oppo uni ies o some oad use s o use all so s o ime-sa ing icks.
In e sec ion poin s and equen u ning condi ions c ea e dange ous si ua ions, hus he
o e all a ic pic u e becomes seemingly uncon ollable.
The a ic condi ions a an in e sec ion ha e a speci ic cha ac e , due o he exis ence
o poin s whe e ehicle lows in e sec wi h each o he and ehicle lows wi h pedes ian
lows. These poin s o con ac a e called „con lic poin s”, as hey a e whe e collisions a e mos
likely o occu . In he case o he in e sec ion o wo oads wi h
X-shaped wo-way a ic (Figu e 2a), 32 possible „ ehicle- ehicle” con lic poin s can be
de e mined [5-11], o which 16 in e sec ion poin s ( ed colo ), 8 sepa a ion poin s (g een
colo ) and 8 me ging poin s (blue colo ), as well as 8 possible „ ehicle-pedes ian” con lic
poin s (whi e colo ) [12].
As a ule, in e sec ion poin s ep esen he g ea es po en ial haza d, since he se e i y
o he consequences o a oad acciden is g ea e han in he case o a oad acciden a he
10 O. Pădu e, V. Plămădeală, V. Goian
Jou nal o Enginee ing Science June 2025, Vol. XXXII (2)
poin s whe e he lows sepa a e o me ge. The numbe o con lic poin s and he po en ial
dange o he in e sec ion inc eases [12]:
• as a ic in ensi y inc eases;
• in he absence o di ec ion es ic ions;
• when he numbe o a ic lanes inc eases;
• when he wid h o he oadway inc eases;
• in he absence o es ic ions on he choice o lanes o he in e sec ion o ehicle
and pedes ian lows e c.
Figu e 2. Possible con lic poin s in an in e sec ion [8]:
a) X-shaped in e sec ion; b) oundabou in e sec ion.
F equen in e sec ions and junc ions o seconda y oads wi h he main oad hinde he
smoo h low o a ic on he main oad, inc easing he po en ial isk o oad acciden s along
i s en i e leng h.
The isk o a a ic acciden inc eases, in pa icula , when a ic in ensi y on seconda y
oads inc eases. In he absence o means o di ec ing a ic, he wai ing ime a he en ance
om he seconda y oad o he main oad can be qui e long. This causes d i e s on he
seconda y oad o ake dange ous ac ions o educe he wai ing ime, e.g. speeding up in
o de o „squeeze h ough”.
Mul i-lane oundabou s, al hough hey can inc ease a ic handling capaci y, can
c ea e new con lic poin s be ween a ic pa icipan s (Figu e 3). When a oundabou has
only one a ic lane, a ic usually lows smoo hly. Howe e , in he case o mul i-lane
oundabou s, ehicles choose di e en pa hs based on hei in en ions o accele a e, which
can lead o pa h in e sec ions.
A he same ime, d i e s c ossing a oundabou end o a el in he mos di ec and
sho es pa h. These in e sec ions a e no always o eseen in he o iginal design and can
c ea e con lic s which, du ing pe iods o ee a ic, can be e en mo e equen , hus
inc easing he isk o acciden s.
a)
b)
Roundabou – elemen o sa e y, ecology and economy 11
Jou nal o Enginee ing Science June, 2025, Vol. XXXII (2)
a)
b)
Figu e 3. Possible con lic poin s a a oundabou in e sec ion mul i-lane oundabou [13]:
a) equi alen in e sec ion; b) non-equi alen in e sec ion.
Ano he nega i e aspec is ha widening he oundabou does no always b ing a
p opo ional inc ease in a ic capaci y. In mul i-lane oundabou s, he cen e lanes a e o en
less used, which leads o an ine icien use o he whole in as uc u e and can cause
conges ion in he pe iphe al sec ions wi h a highe low o ehicles. Thus he o al capaci y
o he oundabou does no always align wi h a ic equi emen s.
2. Solu ions o imp o e oad a ic low and sa e y
In o de o imp o e a ic low and educe he isk o oad acciden s on high- a ic
p io i y oads, i is usually ecommended o design in e sec ions in wo o mo e le els.
Va ious a ian s o such in e sec ions a e used, bu hey equi e la ge capi al in es men s.
The ich expe ience o some coun ies shows ha less cos ly solu ions can be used on
public oads wi h low a ic in ensi y, which success ully imp o e a ic low and sa e y.
P o en and e ec i e solu ions include [9-11]:
• di iding he X-shaped in e sec ion in o wo T-shaped ones;
• applica ion o speed limi ing measu es by aising he in e sec ion a ea, pedes ian
c ossing o applying a i icial speed bumps;
• channeliza ion ( ou ing) h ough he space in he o m o ma kings o sepa a ing
and me ging lows;
• channeliza ion o lows by means o g aded spaces (islands);
• he o ganiza ion o addi ional lanes in o de no o hinde he mo emen o ehicles
en e ing and exi ing he in e sec ion when u ning igh ;
• o ganiza ion o he addi ional lanes in o de no o hinde a ic in he in e sec ion
by ehicles u ning le ;
• o ganiza ion o he le - u n manoeu e a igh - u ning in e sec ions;
• eo ganizing he Y- o X-shaped in e sec ion in o a oundabou in e sec ion e c.
I is o en p oposed o build addi ional a ic lanes o inc ease he h ough capaci y
o busy in e sec ions. P ac ice in many coun ies shows ha inc easing he numbe o lanes
12 O. Pădu e, V. Plămădeală, V. Goian
Jou nal o Enginee ing Science June 2025, Vol. XXXII (2)
a in e sec ions leads o an inc ease in he numbe o oad acciden s. No wegian s udies show
ha a e widening he in e sec ion, he numbe o oad acciden s wi h inju ies inc eases on
a e age by 10% and he numbe o oad acciden s wi h p ope y damage doubles. This
phenomenon is explained by he ollowing [11]:
• he wide oad in he in e sec ion causes d i e s o inc ease speed o c oss he
in e sec ion as e ;
• he wide oadway inc eases he leng h o he pedes ian c ossing, he e o e also
he leng h o ime pedes ians is on he oadway side;
• addi ional a ic lanes inc ease he willingness and possibili ies o change lanes in
he icini y o he in e sec ion, which inc eases he isk o oad acciden s no only a he
in e sec ion i sel bu also in he icini y o he in e sec ion.
The e o e, in o de o inc ease he passing capaci y o conges ed in e sec ions,
nowadays mo e and mo e o en, he eo ganiza ion o hese in e sec ions in o oundabou s
is applied. The aim and pu pose o oundabou in e sec ions a e he ollowing [14]:
• dis ibu ion o oad lows in nodes wi h a complex s uc u e and a la ge numbe o
in e sec ing oads;
• inc easing he h ough capaci y o he in e sec ion and educing wai ing ime in
on o he in e sec ion;
• inc ease oad a ic sa e y;
• a ic calming;
• c ea ing an a chi ec u al s yle speci ic o he u ban en i onmen ;
• in oducing con enien o ms o a ic managemen o le - u ning and u ning
a ic lows;
• educing noise and a ic speed when loca ing junc ions in close p oximi y o
medical and educa ional ins i u ions e c.
The o ganiza ion o oundabou s is no ecommended: on oad sec ions wi h a
longi udinal g adien o mo e han 4%; a he beginning and end o oad sec ions wi h long
slopes and amps; in he immedia e icini y o ailway le el c ossings; when ehicles wi h an
inc eased gauge size o mo e han 25% a e p esen in he a ic low.
3. Ad an ages and disad an ages o o ganizing oundabou s
Roundabou o ganiza ion has he ollowing ad an ages [3,7,11,14,15]:
educing he heo e ical numbe o „ ehicle- ehicle” con lic poin s om 32 o 8
(Figu e 2b), o which 4 sepa a ion poin s (g een colo ) and 4 me ging poin s (blue colo ), as
well as 8 possible ehicle-pedes ian con lic poin s (whi e colo );
elimina ing he a ea, whe e he mos se ious oad acciden s occu , wi h he help o
he cen al island, which „co e s” he a ea o he mos dange ous in e sec ion con lic poin s;
he comple e elimina ion o he isk o se ious head-on collision oad c ashes, wi h
only he less dange ous con lic poin s o sepa a ion and me ging o oad lows, which educe
he likelihood and se e i y o oad c ashes;
low speed o cing by design, which o ces d i e s o slow down on en y, educing
he isk o se ious c ashes;
achie ing he sel - egula ing p ope y inhe en o oundabou s, which ensu es a
cons an unin e up ed low o a ic a low speed, as opposed o a ic ligh ou ing;
Roundabou – elemen o sa e y, ecology and economy 13
Jou nal o Enginee ing Science June, 2025, Vol. XXXII (2)
one-way ou ing o a ic inside he ci cle, which does no cause psychological
s ess on he d i e 's pa due o he need o moni o a ic om o he di ec ions when
wai ing o he in e sec ion en y in e al;
exclusion o le - u n si ua ion and u ning maneu e om oncoming a ic;
low a ic speed, due o he smoo h and calm o a ion a ound he cen e island,
which allows d i e s o adequa ely assess he a ic si ua ion and espond quickly, and in
case o a oad acciden , he consequences, as a ule, do no become se ious o he occupan s
o he ca , being limi ed only o damage o he ehicle body;
he slow decele a ion o he a ic low on he ci cle, which educes he numbe o
b aking – s opping – accele a ion, helps o educe he nega i e impac o anspo on he
en i onmen (emissions, noise);
achie ing mo e e icien a ic o ganiza ion when passing h ough a junc ion wi h
4 o mo e oads;
educed capi al cos s compa ed o mul i-le el junc ions;
educed main enance compa ed o signalized in e sec ions, which equi e cons an
elec ici y, epai s and calib a ion;
lowe long- e m cos s; once buil , a oundabou can ope a e o decades wi h
minimal in e en ion;
adap abili y, which allows he e ec i e use o oundabou s in a ious ypes o
in e sec ions: om u ban, mode a ely a icked in e sec ions o majo highway in e sec ions;
inc ease a ic sa e y by 1.5-3 imes compa ed o o he ypes o in e sec ions a he
same le el;
he o ganiza ion o oundabou s helps o educe he numbe o oad acciden s and
he se e i y o hei consequences e c.
Among he disad an ages o he oundabou a e [3,14,15]:
need in la ge a eas o land compa ed o classic in e sec ions, which can be a
p oblem in dense u ban a eas wi h old in as uc u e o buildings close o in e sec ions;
educed a e age a ic speed;
di icul ies in o ganizing he c ossing o pedes ians and cyclis s in he absence o
special in as uc u e;
wai ing ime a he en ance o he ci cle du ing ush hou s, when p io i y is gi en
o ehicles a eling on he ci cle;
di icul ies in o ganizing p io i y o passing ehicles;
con usion o inexpe ienced o un amilia d i e s, oundabou s, which can cause
unce ain y o hesi a ion;
ine iciency in hea y a ic when oundabou s can become conges ed, equi ing
addi ional in e en ions such as empo a y a ic ligh s;
high up on cos s o design, cons uc ion and eloca ion o exis ing in as uc u e;
inc eased isk o ipping o ehicles wi h high cen e o g a i y as a ic speeds
inc ease;
maneu e ing di icul ies o la ge ehicles, pa icula ly a small oundabou s,
equi ing special solu ions such as a e sable cen e islands;
he need o c ea e a ai ly complex sys em o in o ma ion assis ance o d i e s on a ic
condi ions e c.
14 O. Pădu e, V. Plămădeală, V. Goian
Jou nal o Enginee ing Science June 2025, Vol. XXXII (2)
4. Types o oundabou s
In o de o ensu e a uni ied app oach o he pu pose, scope, geome ic pa ame e s,
design and a ic o ganiza ion, oundabou in e sec ions a e classi ied as ollows [3,12,14]:
La ge oundabou s. They a e p ima ily used on oads ou side se lemen s wi h high
design speeds. En e ing he oundabou is pe o med wi h igh u n, d i ing on he
oundabou o wa d and exi ing he oundabou wi h igh u n. The ou e diame e o he
middle island o hese ci cles is 100-120 m (Figu e 4a), he es ima ed design speed –
50 km/h, he numbe o con e ging oads ≤ 4, he es ima ed in ensi y – up o 70 housand
ehicles/24 h, he numbe o lanes on he en ance/exi – 2/2-3/3 and he numbe o lanes
on he ci cle oadway – 2-3.
a)
b)
Figu e 4.
Roundabou in e sec ion [3, 12]:
a) la ge oundabou ; b) medium oundabou .
Medium oundabou s. These a e he mos common in e sec ions o his ype o u ban
and non-u ban oads. They possess a ai ly high h ough capaci y a a small node a ea. The
ou e diame e o he middle island o hese ci cles is 25-80 m (Figu e 4b), es ima ed design
speed – 35-40 km/h, numbe o con e ging oads ≤ 5, es ima ed in ensi y – up o 35-40
housand ehicles/24 h, numbe o lanes on he en ance/exi – 2/2-3/3 and numbe o lanes
on he ci cle oadway – 2-3.
Small oundabou s. Ab oad, his ype o in e sec ion is called compac . I is
ecommended o be used a he nodes o he local oad ne wo k and unk oad ne wo k o
egional signi icance. The ou side diame e o he middle island o such ci cles is 20-25 m
(Figu e 5a), he ou side diame e o he oadway – no mo e han 30 m, he wid h o he 4,5-
5,5 m, design speed – 25 km/h, numbe o con e gen oads ≤ 4, es ima ed in ensi y – up o
20-25 housand ehicles/24 h, numbe o lanes on en y/exi – 1/1 and numbe o lanes on
he ci cle – 1.
A in e sec ions wi h small oundabou s i is possible o o ganize a ma ginal lane o
he middle island o la ge ehicles (Figu e 5b). A such in e sec ions i is no longe logical
o apply he „classical” maneu e ing scheme o he oundabou . He e, he igh u n is passed
h ough he ci cle in a single maneu e , and he en y on o he ci cle akes place om he
s ee ing island angen ially o he middle island.
Mini oundabou s. These a e used on local oad ne wo ks o a ic calming. The
ou side diame e o he middle island o hese ci cles is 13-18 m (Figu e 6a), es ima ed design
speed – 15-25 km/h, numbe o con e ging oads ≤ 4, es ima ed in ensi y – up o 15-20
Roundabou – elemen o sa e y, ecology and economy 15
Jou nal o Enginee ing Science June, 2025, Vol. XXXII (2)
housand ehicles/24 h, numbe o lanes on he en y/exi – 1/1 and numbe o lanes on he
ci cle oadway – 1.
a)
b)
Figu e 5. Roundabou [3, 12]:
a) small oundabou ; b) ma ginal lane o he middle island o la ge ehicles.
A in e sec ions wi h mini oundabou s, as well as a in e sec ions wi h small
oundabou s, a ma ginal lane o he middle island is o ganized o la ge ehicles (Figu e 4b).
The igh u n and he en ance o he ci cle a e iden ical.
Roundabou oad su aces. These (Figu e 6b) ep esen nodes o med in he p ocess o
his o ical de elopmen and o ganized o oundabou a ic. Road su aces, when o ganizing
he oundabou on hem, a e no subjec o sys ema iza ion and classi ica ion. The pa ame e s
o hese in e sec ions a e de e mined by calcula ion o modeling me hods.
The main ini ial da a, in his case, a e he dimensions o he oad su ace, he in ensi y
and composi ion o oad lows, he co espondence ma ix, he a ic managemen schemes
on con e ging s ee s. A hese in e sec ions also he „classical” ci cula mo emen does no
i . T a eling in he ci cle a some exi s migh con inue s aigh ahead in he igh di ec ion,
a o he s go le . The en y on he ci cle, oo, can be pe o med bo h in he o wa d di ec ion
and u ning igh . Es ima ed design speed – 20-40 km/h, numbe o con e ging oads ≥ 3,
es ima ed in ensi y – up o 60 housand ehicles/24 h, numbe o lanes on he en ance/exi
– 1/1-3/3 and numbe o lanes on he ci cle oadway – 2-3.
a)
b)
Figu e 6.
Roundabou [3,12]:
a) mini oundabou ; b) oad su ace wi h oundabou .
22 O. Pădu e, V. Plămădeală, V. Goian
Jou nal o Enginee ing Science June 2025, Vol. XXXII (2)
buildings o signi ican changes o exis ing oad in as uc u e. These modi ica ions can be
cos ly and may be esis ed by he local communi y.
Also, oundabou s a e no always he bes solu ion o all in e sec ions. In he case o
ex emely busy in e sec ions, hey can become o e loaded and cause bo lenecks, especially
du ing ush hou s. In such si ua ions, al e na i e solu ions, such as in elligen a ic ligh s o
zeb a c ossings, may be mo e e ec i e.
7. In e na ional oad acciden s a is ics a e oundabou implemen a ion [1]
Aus alia. In 1981 he esul s o he implemen a ion o 73 oundabou s we e
e alua ed. The e was a 74% dec ease in he a e o oad acciden s, while p ope y damage
om oad acciden s dec eased by 32% and he numbe o oad acciden s in ol ing
pedes ians dec eased by 68%. Fo 3 yea s he e we e no a al oad acciden s.
In 1990, a he 15 h Aus alian Road Resea ch Boa d con e ence, an analysis o oad
acciden s a is ics a 230 in e sec ions in New Wales be o e and a e hei con e sion o
oundabou s was p esen ed. The a e age numbe o oad acciden s a an in e sec ion pe yea
ell by 41.5% om 3.910 o 2.289, he a e age numbe o oad acciden s wi h pe sons inju ed
a an in e sec ion pe yea – by 45.4% om 1.045 o 0.571 and he a e age numbe o pe sons
killed a an in e sec ion pe yea – by 62.5% om 0.024 o 0.009.
Belgium. In Wallonia in he 90s o he las cen u y, he numbe o oundabou s
inc eased 10- old, while he o al numbe o oad acciden s a oundabou s inc eased only 2-
old. In he pe iod 1992-2000, he expe ience o con e ing 122 undi ec ed in e sec ions in o
oundabou s was s udied, while i was ound ha :
he a e age numbe o oad acciden s wi h auma ized pe sons a an in e sec ion
pe yea a e he ans o ma ion was educed by 41.6%, om 1.352 o 0.789;
he a e age numbe o se ious oad c ashes a an in e sec ion pe yea was educed
by 48% om 0.373 o 0.194.
UK. Du ing esea ch in 1984, i was ound ha he annual numbe o oad acciden s a
oundabou in e sec ions a e aged 3.31, o which only 16% we e oad acciden s wi h inju ies
and a ali ies, and he a e age numbe o oad acciden s pe 100 million ehicles passing
h ough oundabou s was 27.5. S udies ca ied ou in his coun y indica e ha oundabou s
ha e led o a dec ease in wai ing imes by up o 20% and a educ ion in oad acciden s by up
o 50% in some egions [23].
Repea ed s udies on he e alua ion o oad acciden s a di e en oundabou s ha e
been ca ied ou be ween 1999 and 2003. I was es ablished, ha he a e age numbe o
oad acciden s a a oundabou pe yea was 1.77, o hese only up o 7% we e oad acciden s
wi h auma ized and a ali ies. Compa ed o 1984, he a e o oad acciden s a oundabou s
has dec eased by 46.5%.
Ne he lands. A he end o 1992, 181 oundabou s we e su eyed in he Ne he lands.
The in e sec ions we e p e iously undi ec ed, bu due o he high a e o a ic acciden s,
hey we e con e ed in o oundabou s as a esul :
he a e age numbe o oad a ic acciden s a an in e sec ion pe yea a e he
ans o ma ion was educed by 51% om 4.9 o 2.4;
he a e age numbe o people auma ized a one in e sec ion pe yea has been
educed by 71.5% om 1.3 o 0.37.
USA. Acco ding o a epo by he Fede al Highway Adminis a ion, he e a e mo e han
7000 oundabou s in he Uni ed S a es and he numbe is g owing. This expansion is
Roundabou – elemen o sa e y, ecology and economy 23
Jou nal o Enginee ing Science June, 2025, Vol. XXXII (2)
suppo ed by da a showing ha , on a e age, oundabou s educe a al c ashes by 90% and
o al c ashes by 75% compa ed o adi ional signalized in e sec ions [23].
Acco ding o a ede al sou ce in 2000 a s udy was conduc ed a 24 in e sec ions
con e ed o mode n oundabou s in he s a es: Cali o nia, Colo ado, Flo ida, Kansas, Kansas,
Ma yland, Sou h Ca olina and Ve mon . The e ec was as ollows: educ ion in he numbe o
oad acciden s – 39%; educ ion in he numbe o oad acciden s wi h inju ed pe sons – 76%.
The abo e-men ioned sou ce epo ed ha a s udy o 15 small, single-lane
oundabou s on he oadway side o a ci cle in Ma yland (2002) showed hei excep ional
e ec i eness. The ollowing esul s we e ob ained: educ ion in he numbe o acciden s oad
acciden s – 60%; educ ion in he numbe o oad acciden s wi h auma ized
pe sons – 82%; numbe o a ali ies – 100%; educ ion in p ope y damage only – 27%.
A mo e ecen s udy o 8 in e sec ions in Ma yland published he ollowing da a:
he a e age numbe o a ic c ashes a an in e sec ion pe yea a e he
ans o ma ion was educed by 75.8%, om 5.9 o 1.43;
he a e age numbe o a ic c ashes pe 100 million ehicles passing h ough he
in e sec ion dec eased by 76.7%, om 1.59 o 0.37 a e he ans o ma ion.
Ano he in e es ing ac : 60 oundabou s ha e been buil in he ci y o Ca mel, Indiana
(mo e han in any o he ci y in he Uni ed S a es) and, as a esul , he e has been an 80%
educ ion in inju ies and a 40% educ ion in oad acciden s [7].
Acco ding o he Ins i u e o Highway Sa e y, mode n oundabou s gene ally show a
educ ion in Ame ican p ac ice:
• o oad acciden s wi h a ali ies o 90%;
• 76% o oad acciden s wi h auma;
• 30-40% o oad acciden s in ol ing pedes ians;
• 10% o oad acciden s in ol ing cyclis s.
A 2004 s udy es ima ed ha con e ing 10% o classic in e sec ions in he US o
oundabou s would ha e p e en ed 51000 a ic c ashes in 2018, including 231 a ali ies
and app oxima ely 34000 oad c ashes wi h auma. I no es ha he s udy co e s single-lane
in e sec ions. Meanwhile, a 2019 Insu ance Ins i u e o Highway Sa e y s udy also ound ha
he sa e y o wo-lane oundabou s also imp o es o e ime as d i e s ge used o he new
oundabou . Resea che s analyzed oundabou in e sec ions buil in Washing on S a e
be ween 2009-2015 and ound ha a ic c ashes a wo-lane oundabou s dec eased by an
a e age o 9%/yea [24].
F ance. An analysis o he esul s o he implemen a ion o 83 oundabou
in e sec ions in F ance in 1986 showed he ollowing indica o s:
he a e age numbe o oad acciden s wi h auma ized pe sons a an in e sec ion
pe yea a e he con e sion was educed by 78.2%, om 1.42 o 0.31;
he a e age numbe o a ali ies pe in e sec ion pe yea has dec eased by 82.4%
om 2.78 o 0.49;
he a e age numbe o pe sons killed a an in e sec ion pe yea dec eased by 87.5%
om 0.16 o 0.02.
Ge many. In 1995, an expe imen was ca ied ou in Ge many in which 13 o dina y
undi ec ed in e sec ions we e con e ed in o mini oundabou s. I was es ablished ha he
use o a mini oundabou ins ead o a egula in e sec ion in an u ban en i onmen leads o
a signi ican educ ion in acciden s and a e age oad acciden damage:
24 O. Pădu e, V. Plămădeală, V. Goian
Jou nal o Enginee ing Science June 2025, Vol. XXXII (2)
The a e age numbe o oad acciden s pe 1 million ehicles passing h ough he
in e sec ion dec eased by 29.1% om 0.79 o 0.56 a e he ans o ma ion;
The a e age numbe o se ious oad acciden s pe in e sec ion pe yea dec eased
by 48% om 0.373 o 0.194.
8. Conclusion
Acco ding o oad acciden s a is ics a oundabou in e sec ions, unlike adi ional
oundabou s, he e a e almos no head-on, igh - u n and le - u n collisions. The easons a e
speed educ ion and one-way a ic. These cha ac e is ics o oundabou s gene ally educe
o al oad c ashes by 35%, oad c ashes wi h a ali ies by 90%, oad c ashes wi h inju ies by
75%, oad c ashes in ol ing pedes ians by 35% and oad c ashes in ol ing cyclis s by 10%.
In conclusion, i is sa e o say ha , wi h he s a ed aim o inc easing oad a ic sa e y,
imp o ing en i onmen al sa e y and inc easing oad capaci y, which educes wai ing imes
a in e sec ions and subsequen ly ansla es in o sa ings, oundabou in e sec ions a e a
g ea solu ion. The o ganiza ion o oundabou s om e e y echnical and a chi ec u al poin
o iew is o majo p ac ical in e es o many coun ies, including he Republic o Moldo a.
Con lic s o In e es : The au ho decla es no con lic o in e es .
Re e ences
1. Mode n oundabou s, I ku sk, 2009. A ailable online: h p:// anspo .is u.edu/downloads/books/
deponen _3.pd (accessed on 24.09.2024) [in Russian].
2. Ukade o , V.V. Imp o ing he o ganiza ion o a ic h ough in e sec ions. Mas e 's hesis, K asnoya sk, 2022,
80 p. [in Russian].
3. Goian, V.; Plămădeală, V.; Beiu, I. O ganiza ion and sa e y o oad a ic. Volume 4. O ganiza ion and sa e y
o ehicle a ic in a ious condi ions and a ic si ua ions. Uni e si y cou se. Tehnica-UTM, Chisinau, RM,
2021, 306 p. ISBN 978-9975-45-721-7, ISBN 978-9975-45-724-8 (PDF) [in Romanian].
4. In e sec ions. Roundabou s. A ailable online: h ps://wiki.z . u/Перекрестки._Круговое_движение (accessed
on 26.09.2024) [in Russian].
5. Onceanu, V.; Voleac, P. Roundabou design conside a ions. A ailable online:
h ps://ibn.idsi.md/si es/de aul / iles/imag_ ile/352-359_2.pd (accessed on 26.09.2024) [in Romanian].
6. Plămădeală, V.; Goian, V.; Beiu, I. O ganiza ion and sa e y o oad a ic. Technical means o o ganizing and
di ec ing oad a ic. Volume 3. Uni e si y cou se. Tehnica-UTM, Chisinau, RMN, 2021, 450 p. ISBN 978-9975-
45-721-7, ISBN 978-9975-45-728-6 (PDF) [in Romanian].
7. Road Usabili y: Roundabou s. A ailable online: h ps://lpgene a o . u/blog/2015/12/21/yuzabili i-
do ozhnogo-d izheniya-k ugo ye- az yazki/ (accessed on 26.09.2024) [in Russian].
8. Goian, V.; Plămădeală, V.; Beiu, I. O ganiza ion and sa e y o oad a ic. No ma i e ac s, sa e y elemen s and
cha ac e is ics o oad a ic. Volume 1. Uni e si y cou se. Tehnica-UTM, Chisinau, RM, 2021, 341 p. ISBN
978-9975-45-721-7, ISBN 978-9975-45-722-4 (PDF) [in Romanian].
9. Onceanu, V. O ganiza ion and sa e y o oad a ic. Elena VI, Chisinau, Republic o Moldo a, 2006, 273 p. ISBN
978-9975-935-94-4 [in Romanian].
10. Onceanu, V.; A mașu, S. Road a ic sa e y managemen and audi . Tehnica-UTM, Chisinau, Republic o
Moldo a, 2011, 240 p. ISBN 978-9975-45-175-8 [in Romanian].
11. Ope a ing p inciples o a oundabou and i s ad an ages o e an X-shaped in e sec ion. A ailable online:
h p://www.ado . u/da a/ iles/s a ic/audi _16.pd (accessed on 26.09.2024) [in Russian].
12. Roundabou s in he Russian Fede a ion. A ailable online: h ps://zen.yandex. u/media/ uspdd/k ugo oe-
d ijenie- - -5c1bd62bb7cd5100aad3a9d2 (accessed on 27.09.2024) [in Russian].
13. How o de e mine p io i y a a oundabou ? A ailable online: h ps:// uspdd. u/jou nal/62-k ugo oe-
d izhenie-p io i e / (accessed on 27.09.2024) [in Russian].
14. Me hodological ecommenda ions o he de elopmen and implemen a ion o measu es o o ganize a ic.
Inc easing he e iciency o using oundabou s. A ailable online: h ps:// iles.s oyin . u/
Da a2/1/4293734/4293734704.pd (accessed on 28.09.2024) [in Russian].
Roundabou – elemen o sa e y, ecology and economy 25
Jou nal o Enginee ing Science June, 2025, Vol. XXXII (2)
15. Roundabou s: p os, cons, acciden s a is ics. A ailable online: h ps://a oshkolamos . u/a icles/k ugo ye-
pe ek es ki (accessed on 28.09.2024) [in Russian].
16. The second s age o he Piska e skaya in e change has opened in S . Pe e sbu g. A ailable online:
h ps:// opdialog. u/2014/11/29/ -pe e bu ge-o k ylas- o aya-oche ed-piska e skoj- az yazki/ (accessed
on 28.09.2024) [in Russian].
17. The Hippod ome in e sec ion has aken away he Haabe s i Ci cle's i le as a a ic jam magne . A ailable
online: h ps:// us.pos imees.ee/6244032/pe ek es ok-u-ippod oma-o ob al-u-k uga-haabe s i- i ul-
magni a-p obok (accessed on 27.09.2024) [in Russian].
18. Amb osi, G .; Amb osi, E. Tu bo-gy a ion as a me hod o imp o ing oad a ic sa e y. In: Ma e ials o he
na ional scien i ic-p ac ical con e ence „T anspo : enginee ing, economics and managemen ”, Chisinau TUM,
2017, p. 59-62. ISBN 978-9975-45-511-4 [in Romanian].
19. D a new s anda d o oundabou s. A ailable online: h p:// ansspo . u/2017/09/25/p oek -no ogo-
s anda a-na-kolce ye-pe esecheniya/ (accessed on 25.09.2024) [in Russian].
20. Tu bine- ing in e changes: he end o a ic jams! A ailable online: h ps://hodo .lol/pos /159468/ (accessed
on 30.09.2024) [in Russian].
21. England's „Magic Roundabou ” le s ca s na iga e six ci cles. A ailable online: h ps://c s.o g.ua/
news/2016/08/05/ olshebnaya_k ugo aya_ az yazka_ _anglii_p opuskae _a omobili_che ez_shes _kole s_
ideo_35620 (accessed on 30.09.2024) [in Russian].
22. Capsky, D.V. T a ic managemen . Acciden a e: analysis, assessmen , o ecas ing. S udy guide o s uden s
majo ing in 1-44 01 02. T a ic managemen , Minsk, Bela us, 2023, 439 p. ISBN 978-985-583-849-5 [in
Russian].
23. Roundabou speed limi . A ailable online: h ps://www. opgea . o/sens-gi a o iu- i eza-legala/?u m_
sou ce=cha gp .com (accessed on 30.09.2024) [in Romanian].
24. Why we need oundabou s: s udying acciden s a is ics. A ailable online: h ps://110km. u/a /k ugo ye-
pe ek es ki-udobno- odi elyam-bezopasno-peshehodam-134693.h ml (accessed on 26.09.2024) [in
Russian].
Ci a ion: Pădu e, O.; Plămădeală, V.; Goian, V. Roundabou – elemen o sa e y, ecology and economy. Jou nal o
Enginee ing Science. 2025, XXXII (2), pp. 7-25. h ps://doi.o g/10.52326/jes.u m.2025.32(2).01.
Publishe ’s No e: JES s ays neu al wi h ega d o ju isdic ional claims in published maps and
ins i u ional a ilia ions.
Copy igh :© 2025 by he au ho s. Submi ed o possible open access publica ion unde he e ms
and condi ions o he C ea i e Commons A ibu ion (CC BY) license
(h ps://c ea i ecommons.o g/licenses/by/4.0/).
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