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Cl318 Transport Engineering Gordon Best 201109204
Street Design Project- Individual Submission
The streetwhichshall be studiedandre-designedforthisprojectisShawlandsCross (fig.1) inthe
Shawlandsareaof SouthGlasgow.It isa commercial centre inamainlyresidential areaof the city,
home to approximately8000 people.The A77PollokshawsRoad (inred) goesfromSouthWestto
NorthEast at a 30mph speedlimit,andtwosmallerroads of 20mph limits linkontothismainroad.
These tributary roadsare Moss-Side Road (inorange) andKilmarnockRoad(ingreen).Allroads
linkingintothe junctionare 2lane dual directionroads,permittingregulartrafficsuchasstandard
cars, lorries,busesandcyclists.All roadshave carparkingbayson both sidesof the road,which
appearto be takingupa car widthportionof the road. Inthe same lanes,busstopsindicate ahigh
level of publictransportusage inthe area.
The roads are relativelyflat,withnonoticeable steepgradientsor hillswhichcouldaffecttrafficin
winteryconditions. Gradientsare showninfigure 2,takenfromheightsabove sealevel from
digimap. Inaddition,the roadsare of reasonable quality,withno large potholespresent,although
there isa clear lossof colourin the trafficmarkingsat the cross, whichcouldleadtoproblemsinthe
future overthe clarityof trafficinstructions.
Fig.1
Fig.2
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Trafficis regulatedusingBritishstandard trafficlightsystemsandphasing,asshowninfigure 1.
The trafficat the junctionismostlymanagedbytrafficlights,butwithGoogle Mapanalysis,police
officersare alsoseentobe guidingtrafficat nearbyjunctions,showingtrafficmanagementsystems
inthe areaare not adequate toallowthe trafficto flow byautomaticandcomputational means
alone.
The road is primarilyusedtoaccessthe city centre of Glasgow,butis alsousedas a local hubfor
shopsand facilitiesinthe area,suchas the Church and pubsnearthe junction.Itcan alsobe usedas
access to othertownsinthe area such as NewtonMearnsandRutherglen. Itparticularlygrowsin
popularityduringfootball gamesatthe nearbyHampdenParkNational Stadium.
In additiontotrafficmovement,the areaiscommonlyusedforparkinganddropoffsforthe nearby
Shawlands Academy andPrimarySchool with1200 and600 pupilsrespectively.Thisresultsinalarge
rise incongestionduringschool hoursandinparticularthe morningandeveningrushhours,ascan
be seeninfigure 3 at 8.30am.
Fig.3
Fig.4
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Junction Operation
The operational degree of saturation (x)anddelaytime of the junctionshall be calculatedusingthe
equations:
Where
qi= flowfor eachlane inpcu per hour.Thisis dividedinto3sections,the morningpeak,the
afternoonpeakandthe interpeakvalue betweenthesetwo.
S=saturationflowinpcu/hour.
g= effective green time inseconds
C= also knownasthe cycle time inseconds
D=delaytime inseconds
The AM peakvaluesare displayedinthe table below.The initialarrival flow wascalculatedintothe
pcu value fromraw data takenfrom my place.Thiscouldallow the Qand X value tobe calculated
usingthe equationabove.
The arrival flowinthese data setsisthe actual flow of PCU perhour duringthe givenpeaktimes
measured.Qisthe approachcapacity,relatedtothe saturationflow,andacts as the capacity inPCU
perhour, showingthe limitforcapacityperhour,where if exceededqueueswillbegintoform.
X isthe degree of saturation,whichisfoundbydividingthe arrival flow byQ.
Some cellsinthe data setbeloware combineddue tosharinglanes.Forexample carsattemptingto
turn rightonto Moss Side Roadwill share laneswithtrafficgoingstraightontoPollokshawsRoad.
The afternoonpeakvalue wascalculatedusingthe same methodwithdifferentraw data fromMy
Place.
The interpeaktime wascalculated usingthe same method.
C
g
S
q
x
i
i
i
i
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(Full datasetsand calculationsare availablein theappendix section.)
The data shows the widespread nature of the congestion, where Moss Side Road shows very little
signof masscongestion.However,ShawlandsCrossshowsanextremely high level of congestion. A
level of 1 forX showsa highlevel of congestion,withanythinghighershowing potentially significant
queuing issues.
The delay times are similar for AM and PM figures, but lower during the IP time, suggesting the
congestionisnota huge issue duringthistime,butmustclearlybe improvedduringrushhourtimes.
The 2 minute wait drivers face coming from Shawlands Cross and attempting to turn right or go
straight on to Pollokshaws during these times of day will likely cause frustration and potentially
cause further issues.
The flowishigheston ShawlandsCrossandKilmarnockRoadat all timesof day,thisis due to these
beingthe mainroadsleadingthroughthe crossand havinga higherspeedlimitthanthe otherroads
inthe cross.All of the roadsin the cross appearto have highsaturationvalues,meaningthatthere is
likelytobe highlevelsof congestionatall peaktimes. Ascanbeenseeninthe table,trafficcoming
fromShawlandsCrossandtryingto turn rightto Moss Side Road will face substantial delay.Withthis
AM
PM
IP
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highsaturationrate, highcongestionisexpected.The phasingshouldthereforebe alteredtoreduce
the saturationrate andtherefore reduce congestioninthe junction. Forexample,trafficcoming
fromMoss Side ispermittedafull 30 secondsto flow,despitehavingaratherlow saturationflow.
Thistime couldbe betterspentinallowingtrafficfromShawlandsCrosstoPollokshawsorMoss Side
Road,where saturationisconsiderablyhigher.
In addition,lane designcouldbe alteredtoallow fora righthand turnonly,and therefore reducing
the flowinthe lane waitingforcars to turn rightwhentheyare planningongoingstraightaheadto
PollokshawsRoad.
Assumptionsweremade forthe Shawlandsto Pollokshaws sectionof roaddue tothe road beingan
opposedflow. Simple equationsare onlyavailable foranunopposedflow.Forthis,aliteral approach
was taken,where itwasknownthat8 cars were approachingpergreenlighttothe flow pergreen
lightcycle.Thisworkedoutas 3.25s percar, andconsiderationswere takenforhow manycars
wouldattempttocross duringthisbrief breakintraffic.Itwas estimated that2 -4 may try,although
thiscouldbe higheror lower dependingonflow.Fourcarswere estimatedtoattempttocrossper
greenlightasthe actual flow.The saturationflow wascalculatedbyworkingbackwardsusingthis
estimatedvalue.
From a non-motoristperspective,the junctionwouldmostlikelyseemimpractical.There are no
noticeable orconsistentcycle lanesalongthe road,meaningcyclistsmustcompete withmotor
vehiclesforspace alongall roads,increasingthe chance of accidentsorproblemsbetweenroad
users.Also,the maincommercial sectorof the townof Shawlandsisalongthe road,and crossingthe
road seemsproblematicdue tothe awkwardshape of the junction.Inorderto cross the road at
sections,pedestriansmustcross3 setsof pedestriancrossing.The new designforthe junctioncould
incorporate all of these concernstomake the junctiona saferand more efficientareaforall those
whouse it. The pedestrianwalkwaysseemtobe of a reasonable qualityintermsof footpathquality,
althoughthe pathsappearto have beenaffectedbywinterfreeze thaw weatheringlikethe roads,
withminorpotholesinplaces.
To summarise the problemsinShawlandsJunction,there isadistinctinefficiencyinthe phasingof
the trafficlights, where carsare givenunsuitable timeforpassing through.Inadditiontomotor
vehicle use,the facilitiesare notinplace fora safe and efficientusage fromcyclists orothernon-
motorised usersof the road.In orderfor thisto be improved,designatedlanesmustbe addedfor
cyclists,andpossiblybusesif there isroomforthisonthe road. The pedestrianusersof the junction
mustbe consideredforthe changesinthe junction.Currentlyitishighlyinconvenientfor crossing
due to the layoutand positionof crossingpoints,inparticularthe NorthtoSouthcrossingof the
A77. This resultsina highpotential foraccidents.Improvementsinall of the above issueswillresult
inan increase insafety,efficiencyinthe junctionintermsof congestion,andalsoimprovethe
economicbenefittothe nearbycommercial areaalongthe cross.
There ishoweverapotential forimprovingthisjunctionsignificantly.If the datafromtrafficcounts
for eachsectionof road can be studied,thenamore efficientphasingplancanbe suggested,
resultinginaloweringof congestion.Thiswill meangreaterefficiencyandsafetyforall those who
use the road. There ispotential forthe roadto be widened,allowingforfacilitiessuchasa cycle lane
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or bus lane tobe added,thiswouldleadtofurthersafety. Inaddition,righthandturnsonlycouldbe
accommodatedforinorder to reduce the overall flow perlane,andtherefore reduce waitingtimes
and congestion. Thiswouldof course have tocompromise the pedestrianfootpath,butif thiscould
be redesignedforbettercrossingpointthen itispossible sucha
wide pathwouldnotbe required.Thiswouldbe downtomore
efficientlyguidingpedestrianstotheirdestinationratherthan
requiringfootpathsinplacespedestrianscouldeasilyfindamore
efficientroute.
Thiswouldreduce the needforthe highnumberof railingsinplace,whichattempttoguide the
pedestriansthe longwayroundtothe inconvenientcrossingpoints,asseeninfigure 5.
The current crossing positionsare markedonfigure 6as red lines,withpossiblenew positions
markedinblue.If thiswasfollowed,thenpedestrianswouldhave lessdistance towalk,and
pavementscouldbe narrowedtoimplementcycle lanes. Thiscouldbe operatedasonce large scale
pedestriancrossingpoint,where all trafficmustwaitforthe pedestriansratherthanparticularroads
stoppingforparticularcrossings.
Fig.6
Fig.5
