Analysis of Rural Road Geometry, it’s Consistency and Safety through Alignment Index in Kaski,Nepal

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 12 Issue: 03 | Mar 2025 www.irjet.net p-ISSN: 2395-0072

Analysis of Rural Road Geometry, it’s Consistency and Safety through Alignment Index in Kaski,Nepal

Prakash Baral1

1Assistant Professor, Civil Engineering, Pokhara University, Pokhara, Nepal

Abstract

Road accidents are major problem these days in rural road of Kaski. Driver, vehicle, road condition as well as weather conditions are mostly liable to causesuchcircumstances.Road geometry and its consistency are basically measure through operating speed, alignment index, vehicle- stability anddriver workload respectively. Safety is burning issues in the field of transportation engineering which can be address only due to consistent design of rural road alignment. This study tries to quantify the influence of alignment index on road safety using operating speed and design speed to predict the crash rate for evaluation of consistency in Methlang-Gyarjati rural road, Kaski. In this paper crash rate prediction model were developed which can be utilized to measure consistency using alignment indices(Average curve length and tangent length ) on two lane undivided rural road for a mixed traffic flow having similar type of topography and geometric characteristics.

Key words: Alignment indices, Safety, Crash rate, Roadway geometry, Rural road

1.INTRODUCTION

VehicleaccidentoccursfrequentlyinthehillyareaofNepal wherevehicleplungeddowntoseveralmetersfromtheroad surface causing a lot of fatalities and injuries every year. Highspeedofvehicles,steeringorbrakefailures,unfamiliar and intoxicated drivers, long duty hours of driver continuously,poorconditionofvehicles,muddyandslippery roads, haphazard overtaking, poor maintenance, loaded cargo,negligenceoftrafficrulesandsignsaremajorcause behindthisscenario.

InNepal,vehicleaccidentwas8406inFY2013/14andthe numberincreasedby08.79percentandreachedto9145in FY2014/15.Likewise,itincreasedto10013inFY2015/16 androseby09.49percentage.Besidethesefacts,numberof vehicles accident increased by 01.65 percentage only and reachedto10178vehiclesinFY2016/17.Frequentvehicle accidenthadoccurredinhillyareaswherevehiclefalldown up to 500m from the road with tremendous increase in fatalities. Human error, poor infrastructure, geological conditions are major aspect causing road accidents.(Bhagat,S.K.,2017) Geometric design inconsistencies are also a vital aspect to cause accidents whicharebecomingseriousissuesthesedaysinNepal.

AccordingtothereportbyWHO,thenumberofannualroad traffic deaths, globally has reached 1.35 million and approximately causes up-to 50 million more injuries. Differentcountriesaretryingtoadoptdifferentmeasuresto minimize it which varies significantly. With rate of 27.5 deathsper1,00,000population,theriskis3timeshigherin low-incomecountriesthaninhighincomecountrieswhere theaveragerateis8.3deathsper1,00,000population.This reflect that road traffic death is disproportionately high among low-income group as seen from the size of their population and number of motor vehicles point of view.(GemechuShiferawet.al,2021)

Geometric design consistency is an important measure in designingaroadaswellasan importanttooltoevaluate safety.Designconsistencyevaluationis gainingpopularity these days due to increase in crash rate. Various methods can be utilized to check the consistency of roadway geometry.Operatingspeed,alignmentindex,vehiclestability and driver workload are mostly common in operation regardingthisaspect.

Road design without safety measures is meaningless. The majorobjectiveofroadtransportistoprovideeasy,safeand efficient service to the road users which could only be achieved through consistent design. On the other hand, if thereisinconsistencyinroadwaygeometrythentherewill beabruptchangesinspeedandworkloadofthedriver.This resultincriticaldrivingmanoeuvrewhichleadstoincrease intheprobabilityofaccidents.

Kaskidistrictruralroadscannotbekeptasideregardingto questioninsafety.Roadcrasheslevelisincreasingovertime along with the growth in the number of vehicles, the population, the road network and the vehicles kilometres driven.

In the aspect of developing countries like Nepal very few studies have been conducted in this regard. This paper preliminaryanalysedthegeometricdesign,it’sconsistency andsafetyonthealignmentofMethlang-Gyarjatiruralroad ofKaskionthebasisofalignmentindexandcrashratewhich can be utilized to remove shortcomings in road safety standard, design and implementation of policies and safe transportationinfrastructureinruralroadsofKaski.

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 12 Issue: 03 | Mar 2025 www.irjet.net p-ISSN: 2395-0072

1.1 Statement of the problem:

Safetyissueismajoraspecttobetakenintoconsideration especiallyinruralroadofKaskidistrict.Everyyeartherate offatalitiesisincreasingwithahugelossoflifeandproperty. Inadequacy in road length, shoulder width, sharp curve, largespeedvariation,lackofproperstructure,inadequacyof drainageetc.aremajorfactorscontributingtohighrateof crashesinsuchruralroads.

1.2 Objectives:

Themajorobjectivesunderthestudyare:

 Toanalysetheruralroadgeometryanditsconsistency basedonalignmentindices.

 Todevelopasafetymodelforanalysisofsafety.

1.3 Significance of the study:

This study will assist planner, designer to maintain consistency in roadway geometry. The safety model develops in thisstudy will helpto reduceaccident inlong run. It also helps to reform NRRS (Nepal Rural Road Standard) as per necessity which assist in consistent roadwaygeometrydesign.Itfinallyprovesto bea helpful tooltoevaluatesafetywhichisnecessaryforsocio-economic developmentofacountry.

2. Literature Review:

Designconsistencyhasbeenevaluatedandstudiedwidelyin thepastcentury.Intheearlypartofthe1980’sresearchers foundpoordesignconsistencyperformancecausedhigher driverworkload.(Article…

The inconsistent design was summarized as “a geometric featureorcombinationofadjacentfeaturesthathavesuch unexpectedly high driver workload that motorist may be surprisedandpossiblydriveinanunsafemanner.”(Messer, 1980).In terms of the designconsistencyconcept,”Design consistencyistheconformanceofahighwaygeometricand operational features with driver expectancy.” Consistent roadway geometry allows the driver to accurately predict theroadwayspathwithlittlecognitiveeffort,inturnleaving muchofdriver’smentalcapacitytobedevotedtoobstacle avoidanceornavigation.(Wooldridgeetal.,2003)

Fitzpatricketal.definedalignmentindicesas“quantitative measures of the general character of a roadway segments alignment. ”In terms of increasing the geometric inconsistenciesalignmentindiceschangeinrelationtothe high rate or large increase of different segments of the roadway.(Fitzpatricketal.,2000)

Basically, horizontal curves are more dangerous which possesseshighercrashratethanstraightsectionsofsimilar length and traffic composition. The increase in crash rate

becomes particularly significant at radii below 200m. (MohammedHameed,2013)

Trafficvolumeonthecurveandmixtraffic,curvefeatures, cross-sectional curve elements, curve section roadside hazard features(clear slope, rigidity and type of obstacle),stoppingsightdistanceatcurveapproach,friction, distance of adjacent curves too influence the safety at horizontalcurvesections.(AliAram,2010)

Polus and Dagan proposed alignment indices which are based on different geometric characteristics in curve roadwaysections.Fromtheirpreliminaryevaluationitwas suggested that such indices hold promise a measure of consistency. (A.Polus et.al., 1987).High rate of change in alignment indices over some length of roadway lead to geometricinconsistencies.

German uses a horizontal alignment index as alignment severity.(StraBenRichtlinienet.al.,1984)

Likewise,invariousstudy,thoughdifferentelementofthe roadway sections including tangent length and major accident record have been used to predict a model which lack consideration of speed. So, this study propose to developasimplemodelbasedoncrashrate(CR)asgivenby earlierestablishedmodelwherecrashesonthemajor,minor fatalitiesarenotclassifiedasintheearlierstudy.

3.

Methodology:

3.1 Study area:

The study area (Methlang-Gyarjati road section) lies at 28014’27”N latitude and 83058’00”E Longitude. It has an elevation of 895m from the mean sea level. This road connectBaglunghighwaywithSarangkotVDC.Itisselected forstudyonthebasisofvariationinthegeometricfeatures whichwasobservedduringpreliminarysurvey.

3.2Data Collection:

Data related to horizontal road alignment are collected throughfieldsurveyforpreliminarytest.

Table-1 SummaryofGeometricdetailsatCurves

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 12 Issue: 03 | Mar 2025 www.irjet.net p-ISSN: 2395-0072

Fatalitiesandcrashesaremeasuresofinconsistencyinrural road.Thedataforthecrashrateiscalculatedbasedonthe predeterminedmodel

CR=0.0041(v85-vd)2+(V85-Vd)+3.4325

Where,operatingspeedofthevehiclesarecollectedthrough mobilesmartsensorsinthefield.

3.3 Data Analysis:

Mostofthealignmentindicesrequirefortheresearchare identified and included in current design studies. Study stretches include a smaller section of road with three horizontalcurveswhichareutilizedforfindinghorizontal alignmentindices.(Table-2)

Table- 2 Horizontalalignmentindices:

AverageRadius ΣR/N

AverageTangentlength ΣTL/N

Averageradiustoroadlength AR/L

Average curvelengthtotangentlength AV.(CL/TL)

Tangent length to average tangent length TL:AV.TL

Differentscatterplotsaremadetoobtaintherelationship between crash rate and various alignment indices parameters.Thescatterplotsarethenutilizetodevelopa safetymodels..Fromthepreliminaryanalysis,itisclearthat AV. (CL/TL) (Figure.1) shows positive relationship with crash rate whereas, Av. CL:RL(Figure.2), AV.R/L(Figure.3) andTL/AV.TL(Figure.4),showsinverserelationshiptocrash rate(CR).Thesummarystatisticsofalignmentindices(Table3)showssignificanceofthestudy. y = 0.0422x + 2.0344 R² = 0.7404

3.4 Model Formulation:

It has been observed that horizontal alignment indices which comprise a proportion between average curve lengthtotangentlength (Table-2)isthemostinfluencing factors to crash rate with(R2=0.7404, RMSE=0.046) and predicted crash rate as (CR=0.042AV.CL/TL+2.034) respectively.

(Figure.1)than other alignment indices in the present study. It shows that with increase in the ratio of average curve length to tangent length there is increase in crash ratewhichshowsinconsistencyinroadalignmentofKaski.

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 12 Issue: 03 | Mar 2025 www.irjet.net p-ISSN: 2395-0072

Regarding to other indices the case is different where increaseinalignmentindicesthereisdecreaseincrashrate whichensureconsistencyandsafety.Thesafetyevaluation model

(Table - 4) shows variation in indices along horizontal curve section which determine inconsistencies along the rural road alignment of study area that are prone to accidentleadingdeclinationinsafety.

Table -4 Safetyevaluationmodel:

4. Discussion:

In previous study (Jeena Jhony et.al, 2019), average curve length, average tangent length was found to be the most influencing factor which also prevail in thisstudy, though predetermined crash rate model were utilized in this study insteadofnumberofaccidentdatacollected.

Similarly,asperevaluationmadefortwolanerural highway forIndianconditionaveragecurvelengthwasfoundtobethe goodalignmentindex.(AnithaJacobet.al,2018).Thevalidityof the result further can be achieved through R2=0.7404 andRMSE value of 0.04699 which is obtained from the analysis.

Further,thepredeterminedmodelofcrashrateWhichisused inthispaperconsideroperatingspeedaswellasdesignspeed which are vital in analysis of rural road geometric design consistencywhichassisttodeterminetheconditionofsafety inMethlang-Gyarjatiruralroad,Kaski.

5. CONCLUSIONS

•Ratioofcurvelengthtotangentlengthandaverage radius to roadway length was found to be the most influencingvariablewiththecrashrateonhorizontalcurves ofrural roadofKaski.

•Evaluationofhorizontalcurveconsistencybasedon crash rate and safety model for selected road section were obtained.

•Highly influencing variables over a study section must be considered to obtain geometric consistency to maintainsafetyinruralroadsofKaski.

•Theresultsoobtainedfromthepreliminaryanalysis of this study may be taken into consideration for vertical alignment. Beside this other factors can also be utilizeforanalysisofroadconsistencyandsafetyinfuture.

ACKNOWLEDGEMENT

TheauthorwouldliketoacknowledgeProfessorDr.Jaswant

Sokhiforhervaluablesuggestionandsupports.

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