Accident Analysis and Prevention

(1)

AccidentAnalysisandPrevention48 (2012) 346–352

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Accident Analysis and Prevention

j ou rna l h o me pag e :w w w . e l s e v i e r . c o m / l o c a t e / a a p

Safety effects of low-cost engineering measures. An observational study in a Portuguese multilane road

Sandra Vieira Gomes

^∗

, João Lourenc¸ o Cardoso

LaboratórioNacionaldeEngenhariaCivil,DepartmentofTransportation,Av.Brasil,101,1700-066Lisbon,Portugal

a r t i c l e i n f o

Articlehistory:

Received23December2009

Receivedinrevisedform2January2012 Accepted7February2012

Keywords:

Before–afterstudy Median

Low-costengineeringmeasures Roadsafety

a b s t r a c t

Singlecarriagewaymultilaneroadsarenot,ingeneral,averysafetypeofroad,mainlybecauseofthe highnumberofseriouslyinjuredvictimsinhead-oncollisions,whencomparedwithdualcarriageway multilaneroads,withamedianbarrier.

Inthispapertheresultsofastudyontheeffectoftheapplicationofseverallowcostengineering measures,aimedatroadinfrastructurecorrectionandroadsafetyimprovementonamultilaneroad (EN6),arepresented.ThestudywasdevelopedbytheNationalLaboratoryofCivilEngineering(LNEC)for thePortugueseRoadAdministrationandinvolvedacomparisonofselectedaspectsofmotorizedtraffic behaviour(trafficvolumesandspeeds)measuredinseveralsectionsofEN6,aswellasmonitoringofroad safetydevelopmentsinthesameroad.Theappliedlowcostengineeringmeasuresallowedareduction of10%intheexpectedannualnumberofpersonalinjuryaccidentsanda70%decreaseintheexpected annualnumberofhead-oncollisions;theexpectedannualfrequencyofaccidentsinvolvingkilledand seriouslyinjuredpersonswasreducedby26%.

1. Introduction

Thecasestudydescribedinthispaperreferstotheanalysisofthe effectofseveralroadsafetymeasuresundertakenonaPortuguese singlecarriagewaymultilaneroad(EN6),followingtheconstruc- tionofanewmotorway(A5),paralleltotheexistingroad,which linksdirectlyLisboatoCascais.Severallowcostengineeringmea- sureswereimplementedthereafter,ona3.7kmlongstretchofEN6 (between3.2kmand6.9km)toimproveitssafetyrecord.

Theevaluationwascarriedthrougha“before–after”studywith acontrolgroup.Astretchofanothersinglecarriagewaymultilane road(theEN125inAlgarve)wasusedascontrolgroup.

AccordingtotheOrganizationforEconomicCo-operationand Development(OECD),integratedprogrammesonroadsafetyaim- ing to reduce accident severity should focus on several traffic systemelements,namelybyadaptationofroadenvironmentchar- acteristicstotheintendedroaduses(OECD,1984).

Theapplication ofroad safetymeasuresis based ongeneral knowledgeontheroadsafetyphenomenon,sometimescomple- mentedbyresultsfromtheanalysisofaccidentdataintheareato becorrected.

∗Correspondingauthor.Tel.:+351218443528;fax:+351218443029.

E-mailaddresses:[email protected](S.VieiraGomes),[email protected] (J.L.Cardoso).

Betterresultsmaybeachievedwithroadsafetyinterventions ifproceduresfortheirimplementationincludethefollowingsteps (CardosoandBairrão,2001):

-Networksafetydiagnosistoidentifylocationswithhighinfluence ofroadcharacteristicsonaccidentoccurrence.

-Safetyanalysisoneachselectedlocationforpotentialinterven- tions,toidentifythemainroadcharacteristicsleadingtosafety issues.

-Selectionandapplicationofappropriatesafetymeasures.

-Safetymonitoringofthecorrectedsitesandevaluationofresults.

Thedecisionprocessforselectingcorrectivemeasurestakesinto accounttheavailablebudgetfortheprogramme,thesafetyissues identifiedbythediagnosisandtheanticipatedbenefitsfromthe potentialsuitablemeasures.Monitoringsafetydevelopmentsfol- lowinginterventionsandassessingtheresultsobtainedarevery importantstepsforenhancingtheefficiencyofthistypeofprocess, sincetheyallowtheimprovementofex-antebenefitestimations, andconsequently,betterfutureinvestmentdecisions.Thisisespe- ciallyrelevantwhentheappliedsafetymeasuresaretransferred fromothercountries’trafficsystems,duetothedifferentresponse of drivers.This paperallows toincrease theknowledgeonthe effectsofsafetyinterventionsspecificallyappliedinthePortuguese roadenvironment, whichcan bedifferentfromotherEuropean countriesduetoparticulardriverbehaviour.

doi:10.1016/j.aap.2012.02.004