Current Future 1 Louw Kannemeyer Contents Road Network Current WIM Use Future WIM Use 2 Authority Paved Gravel Total SANRAL 22 214 0 22 214 Provinces 9 46 548 226 273 272 821 ID: 799917
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Slide1
USE OF WIM IN SOUTHERN AFRICACurrent / Future
1
Louw Kannemeyer
Slide2Contents
Road Network
Current WIM Use
Future WIM Use
2
Slide3Slide4Authority
Paved
Gravel
Total
SANRAL
22 214
0
22 214Provinces - 946 548226 273272 821Metros - 851 68214 46166 143Municipalities 37 680219 223256 903Total158 124459 957618 081Un-Proclaimed (Estimate) 131 919131 919Estimated Total158 124591 876750 000
SA ROAD NETWORK - 2018
Un-Proclaimed
Roads = Public roads not formally gazetted by any Authority
Slide5South Africa has the 10
th
longest total and 18
th
longest paved road network in the world
The National Development Plan states that roads represent one of the largest public infrastructure investments in most countries.
RSA road
replacement cost>R2 trillion
Slide6Freight flow on road and rail (10
th
State of Logistics Survey 2014)
Also important to note that of the person trips recorded in
National Household Travel Survey
, 2013, by transport modes are as follow:
Minibus taxi’s (41.6%)
Private Vehicles (23.4%) Walking (18.5%) – Along road corridorsbusses (10.2%) Trains (4.4%)Other (1.9%)Roads account for 87.9% of Freight and 93.7% of Person TripsMode Choice FactorPercentageTravel time32.6Travel Cost26.1Flexibility9.2Other32.1SOUTH AFRICA ROAD USE
Slide7Total Life Cycle Transportation Costs
Road User Cost is up to 90% of Total Life Cycle Transportation Cost
Very Good
Very Poor
Slide88
SANRAL Traffic Monitoring Stations
Accurate Traffic Data –
Most Important Data Item
Capacity Analysis / Pavement Design / Life Cycle Economics / Toll Income
Slide99
Traffic Monitoring Stations - WIM
Current Active WIM Stations
Slide10Typical RSA WIM Station
Slide11Main Problem - Systematic deviations in WIM observations due to quality/calibration of WIM installation.Available Calibration Methods
On-site calibration of WIM equipmentAutomatic self-calibrationPost-processing calibrationWhy post-processing calibration?Difficult to undertake full-scale on-site calibration (sample/weigh bridge)
WIM calibration tends to “drift” over time
Post-calibration method applied after load measurements. Can be reapplied to old data.
“Truck-Tractor” (TT) method - Calibration based on load observations of population sample of articulated trucks of a certain type and size Development of method – Dr Martin Slavik
/Mr Gerhard de Wet
WIM – Systematic Deviations
21.8 tons
Slide12Poor WIM Installation
Slide1313
Good WIM Installation
Slide14WIM - Random Deviation
Axle load distribution
WIM Random errors and variation in dynamic loads result in:
Measured axle distribution wider than actual static load distribution
Particularly at higher end of distribution
Results in overestimation of percentage “overloaded” axles
Basic adjustment methodology
Observed axle load measurements is the sum ofStatic load of the axle plusWIM error and dynamic impactIf information on WIM error and dynamic impact is knownThen such impact can be “subtracted” from observed axle loadsTo provide the static load of the axleRandom Deviation Correction Important When Quantifying Overload Damage
Slide15“
Expectation-Maximization-Smoothing” (EMS) algorithmApplies a numeric technique using so-called “deconvolution” methodWim errors basically “convolutes” or distorts the static loadDeconvolution removes this convolution from data
Central limit theorem is a special case
Numeric method does not require fitting of Log-Normal distributions
Can also be solved by means of Expectation-MaximizationProblem is that deconvolution is very sensitive to “noise” in dataCan only be used when data relatively free of noise
This problem is solved by incorporation of smoothing algorithm
Smoothing intended to remove noise from data
WIM - Random Deviation
Slide16WIM - Random Deviation
Slide1717
SANRAL OVERLOAD SOFTWARE
15 to 30 %
Vehicles Overloaded – Only
2%
loaded beyond Prosecution Grace
Statistics - Screened Sample versus Population
Slide1818
SANRAL OVERLOAD SOFTWARE
Slide1919
Committee of Transport Officials (COTO)
TMH Standards
Slide20FUTURE WIM USE
Pavement Design/Maintenance
Old – Axle Load Histogram reduced to Equivalent Standard Axle Load per vehicle - E80
Future
–
SARDS Complete Axle Load Histograms used along with Tyre Contact Stress (How load is transferred to Pavement !!!)
20
20(Not to scale)n-shape:- Single Circularn-shape:- Single rectangularm-shape:- Triple rectangular
Slide21FUTURE WIM USE
Overload Control
Old
– Screeners at Static Weigh Bridges
50 to 100 km impact radius
Construction/Operational Costs
Human Factor
Future – WIM-Enforcement Direct Weight Enforcement integrate with Average Speed over Distance (ASOD) – 250+ InstallationsBeen trialled over past 5 yearsAwaiting National Regulator Compulsory Standards Type Approval for ASOD and WIM-EEnd 2018Realtime Integration to SANRAL Central Operations CentreRealtime Tracking of Load Movements Country Wide (OD) Direct Enforcement (Speed/Load)Insurance FraudSecurity ApplicationsAbnormal Permits EnforcementIndustry Self Regulation Verification???2121(Not to scale)
Slide22THANK YOU
Louw KannemeyerEngineering Executive SANRAL
louwk@nra.co.za
www.sanral.co.za
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